Harm Reduction Journal
BioMed Central
Open Access
Research
Effect of filtration on morphine and particle content of injections
prepared from slow-release oral morphine tablets
Stuart McLean1, Raimondo Bruno*2, Susan Brandon1 and Barbara de Graaff2
Address: 1School of Pharmacy, University of Tasmania, Hobart, Tasmania, Australia and 2School of Psychology, University of Tasmania, Hobart,
Tasmania, Australia
Email: Stuart McLean - mclean@utas.edu.au; Raimondo Bruno* - Raimondo.Bruno@utas.edu.au; Susan Brandon - S.Brandon@utas.edu.au;
Barbara de Graaff - Barbara.deGraaff@utas.edu.au
* Corresponding author
Published: 22 December 2009
Harm Reduction Journal 2009, 6:37
doi:10.1186/1477-7517-6-37
Received: 3 August 2009
Accepted: 22 December 2009
This article is available from: http://www.harmreductionjournal.com/content/6/1/37
© 2009 McLean et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background: Injections of mixtures prepared from crushed tablets contain insoluble particles
which can cause embolisms and other complications. Although many particles can be removed by
filtration, many injecting drug users do not filter due to availability, cost or performance of filters,
and also due to concerns that some of the dose will be lost.
Methods: Injection solutions were prepared from slow-release morphine tablets (MS Contin®)
replicating methods used by injecting drug users. Contaminating particles were counted by
microscopy and morphine content analysed by liquid chromatography before and after filtration.
Results: Unfiltered tablet extracts contained tens of millions of particles with a range in sizes from
< 5 μm to > 400 μm. Cigarette filters removed most of the larger particles (> 50 μm) but the
smaller particles remained. Commercial syringe filters (0.45 and 0.22 μm) produced a dramatic
reduction in particles but tended to block unless used after a cigarette filter. Morphine was retained
by all filters but could be recovered by following the filtration with one or two 1 ml washes. The
combined use of a cigarette filter then 0.22 μm filter, with rinses, enabled recovery of 90% of the
extracted morphine in a solution which was essentially free of tablet-derived particles.
Conclusions: Apart from overdose and addiction itself, the harmful consequences of injecting
morphine tablets come from the insoluble particles from the tablets and microbial contamination.
These harmful components can be substantially reduced by passing the injection through a
sterilizing (0.22 μm) filter. To prevent the filter from blocking, a preliminary coarse filter (such as
a cigarette filter) should be used first. The filters retain some of the dose, but this can be recovered
by following filtration with one or two rinses with 1 ml water. Although filtration can reduce the
non-pharmacological harmful consequences of injecting tablets, this remains an unsafe practice due
to skin and environmental contamination by particles and microorganisms, and the risks of bloodborne infections from sharing injecting equipment.
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Background
It is common for many injecting drug users to prepare
injections from tablets that are designed for oral administration [1,2]. Tablets contain therapeutically inactive
ingredients to facilitate the lubrication, disintegration and
dissolution of the dosage form [3]. These ingredients
include talc, cornstarch, cellulose, magnesium stearate
and waxes, which are not water soluble and their injection
can cause complications. After injection into any blood
vessel, particles will move downstream until they encounter a vessel too small to pass, where they lodge forming an
embolism. Blockage of a vessel causes ischemic damage
through a reduction in blood supply to the tissue downstream and can result in necrosis of the distal tissue. For
example, injection of particles into a peripheral vein can
lead to pulmonary granulomas, pulmonary oedema,
emphysema and pulmonary fibrosis and hypertension
[4,5]. Smaller particles (< 3-4 μm) can pass through capillaries and remain in the circulation until sequestered by
the mononuclear phagocytic system, mainly in the liver
and spleen [6]. Intra-arterial injection, whether deliberate
or accidental, can impair blood supply to a limb and
cause severe tissue ischemia and necrosis, leading to
amputation [7].
Adverse reactions to illicit drug injections are commonly
aggravated by infections due to the non-sterile methods of
preparation and injection procedures. This is seen with
local skin and soft tissue infections, which are the most
common cause of hospital admissions of injecting drug
users [8]. Filterable contaminants in drug injections contribute to many other cardiovascular and infectious complications [9,10].
Although appropriate syringe filters can remove particles
from solutions for injection, their use has not become
routine amongst injecting drug users. While there are
many factors contributing to this, including cost, availability and performance of syringe filters, one substantial
reason is the concern of many drug users that some of the
drug would be lost in filtration.
The current study was designed to replicate preparation
and filtration methods used by injecting drug users for
injection of slow-release oral morphine tablets (MS Contin®, also known as MST Continus® in some other countries). This was selected as injection of morphine tablets
was reported as the last drug injected by 15% of the 2270
injecting drug users interviewed in the national 2008 Australian Needle and Syringe Program study [11] and as
injected in the past six months by 47% of the 909 frequent
injecting drug users interviewed nationally in the 2008
Illicit Drug Reporting System study [12]. MS Contin is the
morphine tablet most commonly injected [12]. The current study aimed to compare the effectiveness of different
http://www.harmreductionjournal.com/content/6/1/37
types of commonly used filters on their ability to reduce
particle content, and also their effect on amount of morphine remaining in the filtered solution.
Methods
Procedures used by injecting drug users
A survey of injecting drug users in the Hobart area (Tasmania, Australia) presenting to needle and syringe distribution outlets (n = 260) was conducted to determine the
filtering methods they applied on their last occasion of
morphine injection [13,14]. One-third (29%) had not
used any filter; 41% used cigarette filters (34% hand-rolling cigarette filters); 21% used 0.22 μm syringe filters
accessed through needle and syringe outlets. Minorities
reported use of 0.45 μm syringe filters (2%), cotton balls
(3%), combinations of cigarette and syringe filters (3%)
or other makeshift filters (such as tampons, 1%). Injecting
drug users in the Hobart area (n = 11) subsequently participated in detailed interviews to describe how they prepared injections from tablets and their filtration
procedures. The methods used in this laboratory study are
based on these methods.
Extraction of morphine from tablets
One sustained-release 60 mg tablet of morphine sulfate
(MS Contin®, Mundipharma, UK) was wiped with a sterile
swab containing 70% isopropyl alcohol (Briemarpak,
Briemar Nominees, Australia) to remove the orange coating (replicating the process used by injecting drug users),
then placed on a glass petri dish to dry. The tablet was
then extracted using either cold or hot Water for Injection
BP (Pfizer, Australia). In the cold method, the tablet was
thoroughly crushed using a glass mortar and pestle, and
mixed with 3.0 ml water. The mixture was then stood for
5 min with occasional stirring. Injecting drug users
employ a variety of improvised methods, such as crushing
the tablet between two spoons. However, it was considered preferable to use a single, reproducible method in
this study, although it is probably more efficient than the
improvised methods and may result in fewer large particles.
The resulting drug extract was either kept for filtration,
examined for particle content by light microscopy or analysed for morphine content by high performance liquid
chromatography (HPLC). The mixture was transferred
into a 5 ml plastic specimen tube for particle counting or
a 50 ml volumetric flask for morphine analysis. The effect
of different methods of filtration on the particle and morphine content of the extracts were also examined. Control
solutions were prepared in an identical manner except
that the tablet was omitted.
In the hot method of morphine extraction, the tablet was
crushed by a porcelain pestle in a small (3 cm diameter, 4
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Harm Reduction Journal 2009, 6:37
cm high), round nickel crucible and the remnants adhering to the pestle were scraped into the crucible. Then 3.0
ml water were added and the crucible placed on a hot
plate and gently boiled, with mixing, for 30-45 s by which
time the mixture appeared to be clear and melted wax
could be seen floating on top. The mixture was then stood
on the bench until it felt cold to touch (about 5 min)
before further treatment as described for the cold preparations.
It is important to note that cold extraction methods are
recommended by Australian Intravenous Drug Consumer
groups
(Network
Against
Prohibition
http://
www.napnt.org/health/filtering_pills.htm; Safer Injecting
Net
http://www.saferinjecting.net/injecting-ms-con
tin.htm) due to a perception of loss of active dose following hot extraction techniques.
Filtration
Cigarette type filter
A filter used for hand-rolled cigarettes (Ranch Slims, Stuart Alexander & Co., Australia) was cut down the side and
the encircling paper removed. Following precisely the
methods reported by injecting drug consumers, the filter
was placed in the drug extraction mixture and moved
around with the tip of a 5 ml syringe (Luer-Lok, sterile, BD
Medical, Melbourne, Australia) until it became saturated
with the liquid. The tip of the syringe was gently pressed
against the side of the filter and the mixture slowly drawn
up. This was repeated at two other sites on the filter, and
the filter usually became blocked before all of the liquid
was drawn up. A second filter was added to enable the filtration to continue until there was no mixture left.
As described for the unfiltered extract, the filtrate was kept
for further filtration, particle counting or morphine analysis. Two successive 1 ml rinses of water were added to the
mortar or crucible and, after moving the filter around in
the liquid, taken up into the syringe and added to the first
filtrate. With the hot preparation method, each rinse volume was briefly boiled then cooled before filtration. All
containers were tared and weighed again at different
stages to estimate the volumes collected. Despite the presence of tablet constituents, it was assumed that the specific gravity of all the mixtures was that of water to enable
the volumes to be calculated. Aliquots of each rinse were
taken for morphine analysis.
Cotton ball filter
A cotton ball (Home Brand Cotton Balls, Australia) was
cut into four equal parts which were rolled into smaller
balls. One small ball was placed in the drug extraction
mixture and gently moved around with the tip of a 5 ml
syringe to absorb the liquid. The mixture was taken up
into the syringe and treated as described for the cigarette
type filter.
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Syringe filter (0.45 or 0.22 μm)
The mixture was taken up into a 5 ml syringe fitted with a
19G needle. The needle was removed and replaced by a
0.45 or 0.22 μm sterile syringe filter (33 mm diameter,
Millex, Millipore, Ireland) and the syringe contents were
slowly pushed through the filter. In some experiments the
filter was flushed with a 1 ml rinse volume of water.
Combined filters
After initial filtration through a cigarette type filter, followed by two 1 ml rinses, the combined filtrates were
taken up into a 5 ml syringe and then the needle was
replaced with a 0.45 or 0.22 μm syringe filter and the
syringe contents gently expelled into a container. The filter
was flushed with another 1 ml water.
Analysis of particle content
Glass microscope slides and coverslips were cleaned in
laboratory detergent (Decon 90, Decon Lab., Sussex, UK),
rinsed in tap water, distilled water and methanol, then
dried in air. In some experiments an overnight acid wash
(conc. nitric acid) was included before the water rinses.
A 20 μl aliquot of each sample was pipetted on to a slide
and covered with a 22 × 22 mm coverslip. This volume
filled the area under the coverslip. The slides were viewed
under a light microscope (Gillet and Sibert, London, UK)
in transmission mode. The eyepieces (Leitz Wetzlar, Germany) had reticules which enabled particles of different
sizes to be counted. One eyepiece showed a rectangular
area (360 × 250 μm with 20× objective) and the other a
linear scale (0-10 by 0.1 unit) whose length was 400 μm
with 20× objective. The rectangle and scale were calibrated
using the ruled lines of a Neubauer blood cell counting
chamber (Hawksley, London, UK). Thus the smallest particle that could be measured with the 20× objective was 4
μm (0.1 on the scale) although smaller particles could be
seen and counted. For each sample, five fields were chosen for counting, at the four corners and centre of the coverslip, selected by moving the microscope stage without
looking through the eyepiece. Particles were counted if
they were inside the rectangle, or overlapped the bottom
or right side, but not if they overlapped the top or left side.
Particles were counted in size groups, using the scale and
a factor based on the magnification of the objective to estimate size. For example, particles 50-99 μm were counted
with the 5× objective, and corresponded to scale readings
0.3-0.5. Particles 20-49.9 μm were counted with the 20×
objective and corresponded to scale readings 0.5-1.24.
Clearly this level of precision was not possible, and borderline particles could have been assigned to either of two
adjacent groups. Total particles in each size group were
estimated from the average count per field multiplied by
the ratio of field area/coverslip area (= number of particles
in 20 μl), then by the ratio of the volume of the injection
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(ml)/0.02 ml to give the number of particles in the injection mixture. Counts are given as mean ± SD of three replicate preparations. Photomicrographs of slides were
taken with an Olympus BX50 microscope fitted with an
Olympus DP50 digital camera.
Analysis of morphine content
The tablet extract or its filtrate was made to volume (50
ml) with 0.5% acetic acid. About 5 ml was filtered
through a syringe filter consisting of a nylon prefilter and
0.45 μm filter (Chromacol, UK). This step was required to
remove particles before HPLC analysis. The relatively large
volume and acidic pH was expected to maximise the dissolution of any morphine that remained in the particles,
and to minimise any retention by the filter. An aliquot of
this filtrate was diluted ten-fold and analysed, in duplicate, by HPLC using a Varian 9010 instrument (Varian,
Australia), a C18 reversed-phase column and UV detection at 286 nm. The mobile phase was 90% phosphate
buffer (50 mM, pH 3) and 10% methanol, and flow rate
0.7 ml/min. Injections were made using a 20 μl loop.
Standard solutions were prepared from morphine sulfate
BP (British Drug Houses, London, UK) and there was no
internal standard. The retention time of morphine was 4.2
min. Calibration curves from 2.5 - 200 μg/ml were prepared each day and linearity was excellent (r2 > 0.99). As
the morphine content of the tablets is given in mg morphine sulfate, we have done the same with the morphine
recovered from the tablets.
Results
Cold extraction, unfiltered
The outer coating was readily removed with an alcohol
swab and the tablet crushed easily although continued
grinding did not result in an ever-finer powder since the
waxy nature of the powder resulted in some re-compaction.
The crushed tablet suspended in cold water gave an
opaque suspension with a milky appearance (Figure 1).
Macroscopic particles were evident on the wall of the tube.
The mean morphine content (as morphine sulfate) was
56 ± 2 mg from 60 mg tablets (Table 1). Microscopic
examination showed many particles ranging in size from
> 400 μm to < 5 μm (Figure 2A). Particles were not uniformly distributed across the coverslip area. Most of the
fields counted were crowded and heterogeneous, making
it difficult to count every particle, and the fields were usually dissimilar. The larger particles (> 50 μm) tended to be
amorphous in shape and to some extent appeared to be
agglomerations of smaller particles (Figure 2B). In counting the particles, the size group was taken to be that of the
agglomeration, regardless of how friable it appeared. Thus
the assignment of particles to size categories was based on
a subjective judgement of whether they appeared to be
separate or joined. Small particles (< 5-10 μm) sometimes
Figure 1mixtures (cold extraction)
Injection
Injection mixtures (cold extraction). Each mixture was
prepared from one tablet as described in Methods. 1, unfiltered; 2, cigarette filtrate; 3, cigarette then 0.45 μm filtrate.
drifted across the field, and had to be counted quickly
while they remained in view. However, some particles
would have been missed. The smallest particles (< 5 μm)
were generally too numerous to count accurately, and
their counts represent a minimum number.
In some preparations regular crystalline shapes were seen,
with sizes ranging from rectangles of 10 μm × 25 μm, to
rods of 1-2 μm × 5-10 μm (Figure 2C and 2D). Treatment
with weak acid (0.5% acetic acid) dissolved the crystals.
This, together with their shape, and the absence of other
likely candidates in the tablet formulation, suggested that
the crystals were morphine hydrate, which precipitated
because of the alkalinity of the glass. This was confirmed
by examining an extract which gave abundant crystals on
the standard glass slides. The same extract gave no crystals
on either glass slides which had been soaked overnight in
nitric acid, or plastic slides. Because their formation was
considered to be artifactual, the crystals were not included
in the particle count. All slides were examined when
freshly-prepared as crystal formation increased with time
on the slide.
A solution of morphine sulfate 60 mg in 3 ml Water for
Injection had a pH of 4.6. An aliquot (50 μl) was mixed
with an equal volume of 50 mM NaOH, resulting in the
formation of masses of small rods of the same appearance
as those found in the tablet extracts. The cold unfiltered
tablet mixture had a pH of 6.4, which was unchanged after
filtration through the cigarette filter or 0.45 μm or 0.22
μm filters.
Figure 3 shows the number of particles sized 5 μm and
larger in the total injection volume for three preparations:
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A
100 ȝm
B
100 ȝm
C
100 ȝm
D
10 ȝm
Figure 2in unfiltered mixture (cold extraction)
Particles
Particles in unfiltered mixture (cold extraction). Photomicrographs of particles from a single preparation.
control (no tablet), cold extraction and hot extraction.
Figure 4 shows the additional particles in the smallest size
group (< 5 μm) of the same preparations, plotted separately because their counts were an order of magnitude
greater than for the larger particles. The upper panel of Figure 3 shows the particle counts in unfiltered preparations.
Even in the absence of a crushed tablet, some small (up to
20 μm) particles were found (Control: Unfiltered), reflecting contamination from the local environment. The unfiltered cold tablet extract produced a much larger number
of particles of all sizes, with the numbers tending to
increase as the size became smaller (Figure 3, Cold: Unfiltered). Although not apparent in Figure 3, there were also
significant numbers of particles in the largest size group (>
400 μm), 12,000 ± 14,000 in the 3 ml injection volume.
The large SD shows the inherent variability of the particle
counts.
Cold extraction, filtered
Two cigarette filters were required to enable the mixture to
be taken into a syringe without the filter being blocked.
The filtrate was milky, like the unfiltered mixture, but it
was also more translucent and there were fewer particles
on the wall of the tube (Figure 1). Only about half (1.7
ml) of the 3 ml water used to prepare the mixture could
be recovered, with the remaining liquid remaining in the
wet filters (Table 1). The mean morphine content of the
filtrate was 32 mg, which is the amount expected to be in
this fraction (1.7/3.0) of the total volume of extract. This
indicates that the morphine was not binding to the filter,
but was being retained because some of the solution was
held up in the filter. Two successive 1 ml rinses with water
recovered most of the remaining morphine (Table 1).
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Table 1: Recovery of morphine after cold extraction and filtration
Filtration
Volume of extract
(ml)
Amount of morphine
(mg)
3.0
55.8 ± 1.9
(N = 4)
Cigarette filter
First filtrate
First rinse
Second rinse
Total
1.7 ± 0.1
1.1 ± 0.0
1.1 ± 0.1
3.9 ± 0.1
31.7 ± 2.3
12.8 ± 0.7
5.9 ± 0.2
50.5 ± 1.8
Cotton wool
First filtrate
First rinse
Second rinse
Total
1.7 ± 0.1
1.1 ± 0.1
1.0 ± 0.0
3.8 ± 0.0
30.5 ± 1.9
10.6 ± 1.2
5.0 ± 0.8
46.1 ± 0.1
0.099
0.45 μm filter
1.9 ± 0.0
33.9 ± 1.0
0.098†
Combined filtration
Cig.+ 0.45 μm filter
Cig. + 0.22 μm filter
5.0 ± 0.2
4.9 ± 0.2
51.5 ± 0.7
51.9 ± 1.4
0.701
0.410
None
P versus cig.
filter alone*
Data are mean ± SD, N = 3 except where otherwise indicated.
*This figure provides a comparison of the amount of morphine recovered through use of the target filter to that recovered through use of a
cigarette filter. Comparisons were made by Mann-Whitney U test (a non-parametric analogue of the t-test), 2-tailed. Results are consistent with
parametric analysis with Games-Howell post-hoc tests with the exception of †0.45 μm filters (p < 0.05). P values greater than 0.05 suggest that it is
unlikely that there is any real difference between the amount of morphine recovered in the two compared techniques.
Some large particles escaped this filtration (Figure 5A),
and there were large numbers of smaller particles and
crystals (Figure 5B). The cigarette filter produced a large
reduction (60-80%) in numbers of particles > 50 μm, a
smaller reduction (10-20%) in particles sized 10-50 μm,
and an increase (20-40%) in the number of smaller particles (< 10 μm; Figures 3 and 4).
The cotton ball filter gave a similar result to the cigarette
filter: a milky filtrate with limited removal of particles
(data not shown). However, the recovery of morphine
may have been slightly lower (Table 1). Also, it was difficult to consistently reproduce the size and density of the
filters.
The 0.45 μm syringe filter gave a clear solution (Figure 1),
but the filter tended to block and it required considerable
pressure to deliver the last of the filtrate. Additionally, the
volume of filtrate was low (1.9 ml), containing only 34
mg morphine. However, this was the amount expected for
the fraction of mixture which was filtered. The filtrate was
relatively particle-free, and this will be described under
the combination filtration procedure.
Hot extraction, unfiltered
The tablet could only be coarsely crushed in the crucible,
but everything melted or went into solution when the
water was boiled. Care was taken to minimise evaporative
water loss, since this tended to increase crystal formation.
On cooling, the mixture became turbid and some large
waxy solids separated. The largest masses were not taken
up into the syringe and were therefore not included in the
particle count. The aspirated mixture had a milky appearance, similar to that produced by cold extraction. The
morphine extraction (59 ± 1 mg, Table 2) was virtually
complete. Microscopic examination showed that, compared to cold extraction, there were fewer particles sized
10 μm or larger, and more sized less than 10 μm (Figures
3 and 4). However, the injection still contained an average
50,000 particles in each of the size groups 50-99 μm and
> 100 μm. Figure 6A shows a field with one very large particle (> 400 μm) and many smaller particles, and panel B
shows what appear to be solidified droplets of melted
wax. The microscopic appearance of hot extractions was
characterised by droplets, particles, and crystals (Figure 6A
and 6D). The larger droplets had inclusions, either particles or other droplets. The formation of many small droplets contributed to the large number of small particles
present.
Hot extraction, filtered
Aspiration through a cigarette filter removed all of the
largest particles (> 100 μm) but only 10-50% of the
smaller particles (Figures 3 and 4). In preliminary experiments it was found that, if the mixture was still warm,
many more of the wax droplets passed through the filter.
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Particle size
9.
9
5-
9.
9
9.
9
-1
-4
10
20
0
4000
3000
2000
1000
9
59.
.9
-1
9
10
9
-4
9
20
0
-9
50
40
0-
.9
0
00
Particles per injection
thousands)
Hot Extract: Cig. Filtrate
5000
>4
9
59.
-1
9
10
.9
9
-4
9
40
0-
>4
10
.9
0
Particle size
-9
9
0
>4
0
9.
9
9.
9
5-
9.
9
-1
-4
1000
00
9
59.
.9
10
-1
9
.9
9
-4
9
20
-9
50
0-
40
00
0
0
2000
20
1000
3000
0
2000
4000
-9
3000
(7112)
5000
50
4000
>4
0
Particle size
Cold Extract: Cig.Filtrate
Particles per injection
(thousands)
5000
10
1000
Particle size
Control Extract: Cig. Filtrate
Particles per injection
(thousands)
2000
10
Particle size
3000
10
10
040
5-
0
0
0
4000
50
Particles per injection
(thousands)
1000
>4
0
9.
9
9.
9
-1
9.
9
-4
0
2000
10
20
50
040
>4
0
10
-9
9
0
Hot Extract: Unfiltered
5000
10
1000
3000
20
2000
4000
-9
9
3000
5000
50
Particles per injection
(thousands)
Cold Extract: Unfiltered
4000
0
Particles per injection
(thousands)
Control Extract: Unfiltered
5000
040
Harm Reduction Journal 2009, 6:37
Particle size
Figure 35 μm or larger in injection mixtures
Particles
Particles 5 μm or larger in injection mixtures. Numbers of particles (in thousands) estimated to be in the total injection
volumes, prepared without a tablet (control) or with cold or hot extraction. Upper panel, unfiltered; lower panel, cigarette filtrate. Total injection volumes are given in Table 1. Values are mean ± SD (N = 3).
As with the cold preparation, nearly all of the dose could
be recovered after 2 × 1 ml rinses with water (Table 2).
Particles per injection
(thousands)
60000
Unfiltered
Cig. Filtrate
0.45Pm Filtrate
0.22 Pm Filtrate
50000
40000
30000
20000
(76,000)
10000
0
Control
Cold
Extraction
Hot
Particles
Figure 4less than 5 μm in injection mixtures
Particles less than 5 μm in injection mixtures. Numbers of particles (in thousands) estimated to be in the total
injection volumes. The unfiltered extracts were passed successively through a cigarette filter then a syringe filter (0.45
μm or 0.22 μm). Values are mean ± SD (N = 3).
Filtration through cotton wool balls gave no better recovery of morphine (Table 2) and, because of the variability
in forming these filters, was not further considered.
The 0.45 μm syringe filter again gave a clear solution with
recovery of 41 mg morphine, which increased to 52 mg
after a 1 ml rinse (Table 1). The particle count is described
after combination filtration.
Combination filtration
Fresh extracts were prepared using cold and hot water and
passed sequentially through a cigarette filter then syringe
filter (0.45 μm or 0.22 μm), with rinses. After both cold
and hot extraction with cigarette filtration, the subsequent
syringe filtration step did not significantly reduce the
recovery of morphine (Tables 1 and 2). Both syringe filters
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http://www.harmreductionjournal.com/content/6/1/37
100 ȝm
100 ȝm
B
Figure 5in cigarette filtrate (cold extraction)
Particles
Particles in cigarette filtrate (cold extraction). Photomicrographs of particles from a single preparation.
greatly reduced the particle count, to levels at or below the
control counts (Figures 7 and 4). In some samples (e.g.
0.45 μm filtrate after hot extraction) there appeared to be
large numbers of small (< 5 μm) particles or droplets.
However, this will require confirmation by re-investigation using cleaner conditions.
Discussion
Morphine in the MS Contin® slow-release tablet is embedded in a complex dual matrix of hydroxyethyl cellulose
and cetostearyl alcohol, designed to release the drug over
12 h [15]. Crushing the tablet disrupts this matrix, allowing the rapid extraction of morphine. The amount of morphine in prolonged-release tablets is permitted to vary by
5% [16] so a 60 mg tablet could contain from 57 to 63 mg
morphine sulfate. The extraction of morphine by cold
water (56 mg) and hot water (59 mg) was therefore essentially complete. None of the filters bound morphine, and
their retention of morphine was due to the volume of liquid which remained. Consequently, rinsing the filters
increased the recovery of morphine. Repeated rinses
brought diminishing recoveries of morphine, and
increased the volume to be injected, and therefore the
number of rinses used in the combined filtration method
was a minimized but nevertheless gave a good recovery
(84-93%) of the extracted morphine. Overall, the extraction of morphine and its recovery after filtration was similar after cold and hot extraction.
The MS Contin® tablet contains a number of constituents
with low or no water solubility which are liable to produce particles in the extract [17]. These include cetostearyl
alcohol, which is a mixture of two waxes: cetyl alcohol (1hexadecanol, mp 49°C) and stearyl alcohol (1-octadeca-
nol, mp 61°C); magnesium stearate (mp 88°C); talc, a
hydrated magnesium silicate; and hydroxyethylcellulose
(a gelling agent which is insoluble in water). The coating
contains other insolubles such as iron oxide, but this was
usually removed in preparing the extracts.
There are advantages and disadvantages in counting particles by microscopy rather than an instrumental method,
such as the Coulter Multisizer which has been used to
study the effectiveness of filters for heroin injections [18].
In this latter study, the instrument required considerable
dilution of the sample (50 μl to 75 ml) with the possibility of dissolution of some particles which would have
been present in the smaller volume to be injected. The
dilution was made with an electrolyte (saline) which may
also have affected particle solubility or aggregation.
Microscopy avoided dilution and enabled examination of
the appearance of particles, which gave insights into their
origin (such as crushed solids, condensed wax droplets,
and crystallised morphine) which in turn can indicate
how they could be removed. However, microscopy necessarily examines only a small part of the total sample, adding to errors as discussed below.
Counting particles, especially in the unfiltered preparations, was inherently variable due to the large amount of
insoluble material and its complex physical form. This
variability also affected instrumental counting, and Scott
[18] considered that variability in the particle counts
made the exact values meaningless although useful for
comparison of filters. In our study counts are presented as
the number of particles in an injection volume in order to
relate the data to health impacts. This required a large
multiplier factor. For example a count of one 100 μm parPage 8 of 13
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Harm Reduction Journal 2009, 6:37
A
C
100 ȝm
100 um
http://www.harmreductionjournal.com/content/6/1/37
B
100 ȝm
D
100 ȝm
Figure 6in unfiltered mixture (hot extraction)
Particles
Particles in unfiltered mixture (hot extraction). Photomicrographs of particles from a single preparation.
ticle in 5 fields using the 5× objective would give an estimated 8,897 particles in the 3 ml dose volume, and one
10 μm particle (20× objective) would give 161,333 particles in 3 ml. If there were no similar particles in the other
two replicate mixtures, then the mean particle counts
would be 2966 for the 100 μm particle and 53778 for the
10 μm particle. The particle counts are therefore reported
in thousands to avoid implying a level of precision which
would be misleading. The counts are indicative estimates
rather than precise determinations, but are nevertheless
able to show that filtering can greatly reduce the number
of particles injected.
The working area for preparing the injections was neither
sterile nor particle-free, since the aim was to reproduce the
typical conditions used for illicit preparations by injecting
drug users. Consequently, a significant number of particles and fibres were found when control injections were
prepared, showing that particles are ubiquitous unless
removed by specific cleaning procedures. Fibres, however,
were not counted as particles since they were present on
control slides and were not considered to be tabletderived. Environmental particles will vary widely according to local conditions but will add to the total particle
burden in the injection. Not using a clean workplace
became a limitation in counting particles in the cigarette
plus 0.22 μm filtrate, in which virtually all tablet-derived
particles had been removed.
The form of the waxes was evidently altered after melting
and re-solidifying, with the formation of wax droplets of
various sizes. Hot extraction resulted in a shift in particle
size distribution, with the formation of more small particles (< 5 μm) and fewer larger particles. However, the
remaining particle burden in unfiltered preparations was
still too large for this to be considered other than harmful
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Table 2: Recovery of morphine after hot extraction and filtration
Filtration
Volume of extract
(ml)
Amount of morphine
(mg)
3.0
58.9 ± 1.3
Cigarette filter
First filtrate
First rinse
Second rinse
Total
2.1 ± 0.1
1.0 ± 0.1
1.1 ± 0.1
4.1 ± 0.1
42.4 ± 0.9
9.1 ± 1.9
2.7 ± 0.1
54.3 ± 2.6
Cotton wool
First filtrate
First rinse
Second rinse
Total
1.6 ± 0.2
1.1 ± 0.0
1.0 ± 0.2
3.8 ± 0.3
35.3 ± 4.4
12.1 ± 2.3
5.2 ± 0.6
52.6 ± 3.1
0.393
0.45 μm filter
First filtrate
Rinse
Total
1.9 ± 0.2
0.9 ± 0.1
2.8 ± 0.2
41.2 ± 2.3
10.7 ± 2.4
51.8 ± 1.9
0.203
Combined filtration
Cig.+ 0.45 μm filter
Cig. + 0.22 μm filter
4.5 ± 0.3
4.3 ± 0.6
52.4 ± 1.6
49.6 ± 2.0
0.400
0.096
None
P versus cig.
filter alone*
Data are mean ± SD, N = 3.
*Comparison of morphine recovery by Mann-Whitney U test (a non-parametric analogue of the t-test), 2-tailed. Results are consistent with
parametric analysis with Games-Howell post-hoc tests.
to inject. Pharmaceutical standards require that, measured
by microscopy, injections of less than 100 ml must have,
in total, no more than 3000 particles > 10 μm and no
more than 300 particles > 25 μm [16]. The hot unfiltered
morphine tablet preparations had, in the total volume of
3 ml, an average 1.1 million particles > 10 μm and
368,000 particles > 20 μm. For the cold preparations, the
numbers of particles were 7.2 million > 10 μm, and 4.0
million > 20 μm.
The aqueous solubility of morphine is critically dependent on its ionization and therefore the pH, as the ionized
form is freely soluble and the free base has a low water solubility (0.25 mg/ml at 35°C) [19]. These authors found
that, at 35°C, the solubility of morphine in water was
13.39 mg/ml at pH 6.35 and 5.75 mg/ml at pH 6.69. This
change in solubility with pH could be explained by the
change in ionization and the low free base solubility. A 60
mg tablet of morphine sulfate (MW = 758.9) contains
45.1 mg morphine (MW = 285.3), or 15.0 mg/ml in the 3
ml extract. Using the amount of morphine sulfate recovered in cold extracts, this concentration would be 14.0
mg/ml. In either case, the concentration of morphine in
the 3 ml extract will be critically close to, or exceed, its solubility, especially as the pH is slightly higher (6.4) and the
temperature was considerably lower (about 20°C). From
the pKa of morphine (8.08) and the buffer equation, pH
= pKa + log10([base form]/[acid form]), it can be calcu-
lated that morphine is 1.8% unionized at pH 6.35 and
2.1% unionized at pH 6.40.
It was considered that morphine crystal formation was an
artifact due to alkalinity in the glass microscope slide or
cover, since they did not form on acid-washed glass or
plastic slides. However, there is a significant risk of formation of morphine crystals in the tablet extracts,, and conditions of preparation could reduce this problem by
decreasing pH or, preferably, increasing the volume of
water. Although morphine will eventually dissolve in
blood this will take some time, and any crystals which
remain undissolved during the brief transit time from
injection site to capillary bed are liable to cause embolisms.
The unfiltered tablet extracts must be considered
extremely harmful as they contained many particles of all
sizes. After intravenous injection, particles will flow
through ever-widening vessels back to the heart and then
they will enter the pulmonary circulation, where the
smaller arteries which are 300-400 μm diameter [20]
could be occluded by the largest particles found in unfiltered mixtures. Arterioles (9-40 μm diameter) and capillaries (7-9 μm diameter) could be blocked by the smaller
particles. Even particles too small to embolize may cause
vascular injury. Small airborne particles (< 2.5 μm) have
been implicated in cardiac and vascular damage, includPage 10 of 13
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Harm Reduction Journal 2009, 6:37
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0
3000
2000
1000
0
1000
50
-9
9
20
-4
9.
9
10
-1
9.
9
59.
9
0
5000
4000
3000
2000
1000
0
>4
0
10 0
040
0
50
-9
9
20
-4
9.
9
10
-1
9.
9
59.
9
Particles per injection
(thousands)
2000
>4
0
10 0
040
0
Particles per injection
(thousands)
3000
2000
1000
0
Particle size
Cold Extract: 0.22 m Filtrate
Control Extract: 0.22 m Filtrate
4000
3000
Particle size
Particle size
5000
4000
>4
0
10 0
040
0
50
-9
9
20
-4
9.
9
10
-1
9.
9
59.
9
1000
4000
5000
Particle size
Hot Extract: 0.22 m Filtrate
Particle size
5000
4000
3000
2000
1000
0
>4
0
10 0
040
0
50
-9
9
20
-4
9.
9
10
-1
9.
9
59.
9
2000
Hot Extract: 0.45 m Filtrate
Particles per injection
(thousands)
3000
5000
>4
0
10 0
040
0
50
-9
9
20
-4
9.
9
10
-1
9.
9
59.
9
Particles per injection
(thousands)
4000
>4
0
10 0
040
0
50
-9
9
20
-4
9.
9
10
-1
9.
9
59.
9
Particles per injection
(thousands)
5000
Particles per injection
(thousands)
Cold Extract: 0.45 m Filtrate
Control Extract: 0.45 m Filtrate
Particle size
Figure 75 μm or larger in syringe filtrates
Particles
Particles 5 μm or larger in syringe filtrates. Numbers of particles (in thousands) estimated to be in the total injection volumes, prepared without a tablet (control) or with cold or hot extraction. Upper panel, 0.45 filtrate; lower panel, 0.22 μm filtrate. Total injection volumes are given in Table 1. Values are mean ± SD (N = 3).
ing endothelial dysfunction and promotion of atherosclerotic lesions [21]. Large numbers of particles of this size
were present in the unfiltered mixtures.
The cigarette filter reduced the number of particles, especially the larger particles. This filter was more effective
when used after hot extraction, but the remaining particle
burden remained too high for injection. Of course, cigarette filters are not designed for liquids. The morphine
recovery from the cigarette filters was nearly complete
(90%) after two rinses. The unfiltered mixtures caused a
block of the syringe filters, but the cigarette filtrate passed
through them, as did the rinse volumes. Scott [18] found
that both 0.22 μm and 0.45 μm syringe filters blocked
with heroin injections, and abandoned them in favour of
5 μm filters. However, these blockages can be prevented
by the use of a preliminary, coarse filter, such as the cigarette filter applied here.
The combination of cigarette filter then syringe filter
mostly gave a good recovery of the extracted morphine.
The 0.22 μm filter is considered to be sterilizing because,
unlike the 0.45 μm filter, it will remove bacteria. In a trial
with injecting drug users [22], it was found that 0.22 μm
syringe filters were effective in removing bacteria from 3
out of 4 injections, while larger pore filters (15 - 20 μm)
were completely inadequate.
Conclusions
When a tablet of slow-release morphine (MS Contin®) is
crushed and mixed with water, the resulting mixture contains millions of particles, of sizes from less than 5 μm to
greater than 400 μm. These particles will cause great harm
if injected into the bloodstream. The number of particles
can be greatly reduced by filtration. A low-porosity syringe
filter (0.45 or 0.22 μm) is most effective, but is likely to
block unless a coarser filter is used first. Little of the morphine is lost in filtration if the filters are rinsed.
Hot extraction does not significantly increase extraction of
morphine, and carries the risk of filtering a warm mixture
which allows wax to pass through the filter, producing
particles when it cools and solidifies. In practice, it is
uncommon for solutions to be left for long before filtra-
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Harm Reduction Journal 2009, 6:37
tion and injection, producing the potential for a substantially greater level of filtrate contamination with wax than
identified in the current study.
It is not possible to prepare an injection of pharmaceutical
standard without clean facilities, as some particles will
remain even after filtration through a syringe filter, and
the injection will not be sterile. Also, the manufacturer
cautions against using Millex® sterile filters for suspensions or emulsions, because they are not designed for this
purpose (Millipore Millex User Guide, 2008). However,
filtration with a 0.45 μm or 0.22 μm filter can remove virtually all of the tablet-derived particles and should be a
standard method of harm reduction for injecting drug
users (a plain language summary of this study is provided
in Additional file 1 in order to facilitate health interventions). The 0.22 μm filter is to be preferred, as it can
remove the organisms (e.g. Staphylococcus aureus, Candida)
which commonly produce cutaneous and systemic infections in injecting drug users [7,8,10]. Although it cannot
remove the much smaller virus particles, including Hepatitis C [23], viral infections are mostly due to blood contamination from shared equipment and are avoided by
not sharing. In one Canadian hospital, the two most common reasons for admission of injecting drug users were
pneumonia and soft-tissue infections [24], both potentially preventable by effective skin swabbing and filtration
of injections. The average daily cost of hospitalization was
$CAN610 ($USD420 at the time of the study), which
makes the use of alcohol swabs (currently <$USD0.02 in
Australia) and filters (<$USD0.90) extremely cost-effective.
http://www.harmreductionjournal.com/content/6/1/37
Acknowledgements
The authors are grateful to Inn Chua for assistance in preparing the photomicrographs, and to Tania Hunt from the Tasmanian Council on AIDS,
Hepatitis and Related Diseases for assisting with organisation of consumer
interviews and surveys, and to the consumers who shared their knowledge
and expertise.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Competing interests
The authors declare that they have no competing interests.
13.
Authors' contributions
SM contributed to the design of the study, carried out the
particle counting, and drafted the manuscript. RB conceived of the study, participated in its design and coordination and helped to draft the manuscript. SB developed
and conducted the morphine assays. BG interviewed the
injecting drug users and summarised their methods. All
authors read and approved the final manuscript.
14.
Additional material
18.
15.
16.
17.
19.
Additional file 1
Plain Language Summary: Effect of filtration on morphine and particle
content of injections prepared from slow-release oral morphine tablets.
Click here for file
[http://www.biomedcentral.com/content/supplementary/14777517-6-37-S1.DOCX]
20.
21.
Degenhardt L, Black E, Breen C, Bruno R, Kinner S, Roxburgh A, Fry
C, Jenkinson R, Ward J, Fetherston J, et al.: Trends in morphine
prescriptions, illicit morphine use and associated harms
among regular injecting drug users in Australia. Drug Alcohol
Rev 2006, 25:403-412.
Fischer B, Cruz MF, Rehm J: Illicit opioid use and its key characteristics: a select overview and evidence from a Canadian
multisite cohort of illicit opioid users (OPICAN). Can J Psychiatry 2006, 51:624-634.
Sinko PJ: Martin's Physical Pharmacy and Pharmaceutical Sciences 5th edition. Baltimore: Lippincott Williams & Wilkins; 2006.
Roberts WC: Pulmonary talc granulomas, pulmonary fibrosis,
and pulmonary hypertension resulting from intravenous
injection of talc-containing drugs intended for oral use. Proc
Bayl Univ Med Cent 2002, 15:260-261.
Gotway MB, Marder SR, Hanks DK, Leung JWT, Dawn SK, Gean AD,
Reddy GP, Araoz PA, Webb WR: Thoracic complications of
illicit drug use: An organ system approach. Radiographics 2002,
22:S119-S135.
Decuzzi P, Pasqualini R, Arap W, Ferrari M: Intravascular Delivery
of Particulate Systems: Does Geometry Really Matter? Pharmaceutical Research 2009, 26:235-243.
del Giudice P: Cutaneous complications of intravenous drug
abuse. British Journal of Dermatology 2004, 150:1-10.
Ebright JR, Pieper B: Skin and soft tissue infections in injection
drug users. Infect Dis Clin North Am 2002, 16:697-712.
Chiang W, Goldfrank L: The medical complications of drug
abuse. Med J Aust 1990, 152:83-88.
Cherubin CE, Sapira JD: The medical complications of drug
addiction and the medical assessment of the intravenous
drug user: 25 years later. Ann Intern Med 1993, 119:1017-1028.
National Centre in HIV Epidemiology and Clinical Research: Australian NSP Survey National Data Report 2004-2008. Sydney:
University of New South Wales; 2009.
Stafford J, Sindicich N, Burns L, Cassar J, Cogger S, de Graaff B,
George J, Moon C, Phillips B, Quinn B, White N: Australian Drug
Trends 2008: Findings from the Illicit Drug Reporting System. Sydney: National Drug and Alcohol Research Centre; 2009.
de Graaff B, Bruno R: Tasmanian Drug Trends 2007: Findings from the
Illicit Drug Reporting System (IDRS). Australian Drug Trends Series No. 5
Sydney: National Drug and Alcohol Research Centre; 2008.
de Graaff B, Bruno R: Tasmanian Drug Trends 2008: Findings from the
Illicit Drug Reporting System (IDRS). Australian Drug Trends Series No. 23
Sydney: National Drug and Alcohol Research Centre; 2009.
Miller DA, DiNunzio JC, Williams RO: Advanced formulation
design: Improving drug therapies for the management of
severe and chronic pain. Drug Development and Industrial Pharmacy
2008, 34:117-133.
British Pharmacopoeia Commission: British Pharmacopoeia London:
The Stationery Office; 2005.
Thomas J: Australian Prescription Products Guide 35th edition. Hawthorn: Australian Pharmaceutical Publishing Co; 2006.
Scott J: Laboratory study of the effectiveness of filters used by
heroin injectors. Journal of Substance Use 2005, 10:293-301.
Roy SD, Flynn GL: Solubility behavior of narcotic analgesics in
aqueous media - solubilities and dissociation constants of
morphine, fentanyl and sufentanil. Pharmaceutical Research 1989,
6:147-151.
Seeley RR, Stephens TD, Tate P: Anatomy and Physiology 7th edition.
New York: McGraw Hill; 2006.
Kang YJ: Toxic responses of the heart and vascular system. In
Casarett and Doull's Toxicology: The Basic Science of Poisons 7th edition.
Edited by: Klaasen CD. New York: McGraw Medical; 2008:699-739.
Page 12 of 13
(page number not for citation purposes)
Harm Reduction Journal 2009, 6:37
22.
23.
24.
http://www.harmreductionjournal.com/content/6/1/37
Caflisch C, Wang J, Zbinden R: The role of syringe filters in harm
reduction among injection drug users. American Journal of Public
Health 1999, 89:1252-1254.
Yuasa T, Ishikawa G, Manabe S, Sekiguchi S, Takeuchi K, Miyamura T:
The particle size of hepatitis C virus estimated by filtration
through microporous regenerated cellulose fibre. J Gen Virol
1991, 72(Pt 8):2021-2024.
Palepu A, Tyndall MW, Leon H, Muller J, O'Shaughnessy MV, Schechter MT, Anis AH: Hospital utilization and costs in a cohort of
injection drug users. Canadian Medical Association Journal 2001,
165:415-420.
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