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Clinical Toxicology
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Methanol toxicity secondary to inhalant abuse in adult men
Erik A. Wallace a; Adam S. Green b
Department of Internal Medicine, University of Oklahoma College of Medicine, Tulsa, OK, USA b Department
of Radiology, Worcester Medical Center, St. Vincent Hospital, Worcester, MA, USA
a
First Published:March2009
To cite this Article Wallace, Erik A. and Green, Adam S.(2009)'Methanol toxicity secondary to inhalant abuse in adult men',Clinical
Toxicology,47:3,239 — 242
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Clinical Toxicology (2009) 47, 239–242
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ISSN: 1556-3650 print / 1556-9519 online
DOI: 10.1080/15563650802498781
Methanol toxicity secondary to inhalant abuse in adult men
LCLT
ERIK A. WALLACE1 and ADAM S. GREEN2
Methanol toxicity secondary to inhalant abuse
1
Downloaded By: [Wallace, Erik A.] At: 15:00 13 April 2009
2
Department of Internal Medicine, University of Oklahoma College of Medicine, Tulsa, OK, USA
Department of Radiology, Worcester Medical Center, St. Vincent Hospital, Worcester, MA, USA
Background. The purpose of this report is to evaluate the presentation, treatment, and outcomes of adults with methanol toxicity from
inhalation of carburetor cleaning fluid fumes. Methods. Retrospective chart review of adults with positive serum volatile screen for
methanol and history of carburetor cleaning fluid fume inhalation. Results. Sixteen patients were admitted 68 times. Eleven Native
American patients accounted for 90% of admissions. Sixty-five cases presented with nausea/vomiting; 27 with intoxication or altered
mental status; 21 with specific visual complaints. About 93% had a pH <7.35, 96% had serum bicarbonate <20 mEq/L, 81% had osmolal
gap ≥10 mOsm/L, and 69% had anion gap >16. Ten had an initial serum methanol level <20 mg/dL, 29 cases 20–49 mg/dL, 19 cases ≥50
mg/dL. Six patients had a measurable serum ethanol level. Of the 29 patients with a methanol level of 20–49 mg/dL, 20 received
intravenous antidote (ethanol or fomepizole); three received an antidote and hemodialysis. All who presented with a serum methanol level
≥50 mg/dL received intravenous ethanol or fomepizole. All visual symptoms resolved before discharge and all patients survived without
sequelae. Discussion. This is the largest reported number of cases of methanol toxicity from the inhalation of carburetor cleaning fluid
fumes and demonstrates a problem with recurrent abuse among some older Native American men. Conclusion. Intentional inhalation of
methanol fumes may produce toxicity. Clinicians need to question patients, especially older Native American men, regarding the possible
inhalation of carburetor cleaning fluid fumes in those who present with an unexplained metabolic anion gap acidosis.
Keywords Methanol toxicity; Carburetor; Inhalant abuse; Native American
Introduction
Methods
Inhalant abuse continues to be a problem in the United
States. More than one million people abuse inhalants each
year, the majority of whom are Caucasian and Hispanic
adolescents.1–4 However, inhalant abuse among adults is
uncommon.1 More than 1,000 products, some of which contain methanol, are available for abuse as inhalants and can
produce varying degrees of toxicity, although methanol toxicity is uncommon.5 Treatment guidelines that include the
use of intravenous ethanol, fomepizole, and hemodialysis
are based primarily on the patient’s serum methanol level on
presentation.6,7 However, outcomes associated with inhalational methanol toxicity have not been studied since the vast
majority of methanol cases are a result of ingestion. In this
report, we describe the presentation, treatment, and outcomes of adults who presented to a community hospital with
methanol toxicity from the inhalation of carburetor cleaning
fluid fumes.
The medical records of adults (age ≥18 years old) who were
admitted to St. John Medical Center in Tulsa, Oklahoma
from January 1, 2000 through December 31, 2006, with a
positive serum volatile screen for methanol were reviewed.
The inclusion and exclusion criteria are shown in Fig. 1.
Variables identified and analyzed were age, sex, race,
number of admissions per patient, location of admission,
treatment received, clinical outcome, and the admission
arterial pH, serum bicarbonate (mEq/L), anion gap, serum
osmolality (mOsm/L), serum methanol (mg/dL), and serum
ethanol (mg/dL). Serum osmolal gap was reported as calculated serum osmolality (mOsm/L) minus measured serum
osmolality (mOsm/L) where calculated serum osmolality =
(2 × (Na + K)) + (BUN/2.8) + (glucose/18).
Statistical analyses were carried out using StatsDirect statistical software (http://www.statsdirect.com) (StatsDirect
Ltd, England) in 2008. Values are reported as percentage or
mean (SD), with p < 0.05 considered statistically significant.
The institutional review boards of The University of
Oklahoma and St. John Medical Center approved this study.
Received 26 June 2008; accepted 23 September 2008.
Address correspondence to Erik A. Wallace, Department of Internal
Medicine, University of Oklahoma College of Medicine, 4502 E. 41st
Street, Tulsa, OK 74135, USA. E-mail: erik-wallace@ouhsc.edu
Results
Sixty-nine patients were identified (Fig. 1). One patient who
had a positive serum volatile screen for methanol was
Clinical Toxicology vol. 47 no. 3 2009
240
E.A. Wallace and A.S. Green
Patients identified with positive
serum volatile screen for methanol
(n = 69)
Patients admitted with diagnosis of
inhalant abuse or methanol toxicity
(n = 69)
Patients who inhaled
products that did not contain
methanol by history (n = 1)
Patients who inhaled
carburetor cleaning
products containing
methanol by history
(n = 68)
Downloaded By: [Wallace, Erik A.] At: 15:00 13 April 2009
No serum methanol
level measured on
admission (n = 10)
Patients with measured
serum methanol level on
admission (n = 58)
Serum methanol
<20 mg/dL
(n = 10)
Treatment
with antidote
(n = 20)
Serum methanol
≥50 mg/dL
(n = 19)
Serum methanol ≥20
and <50 mg/dL
(n = 29)
Treatment with
antidote and
hemodialysis
(n = 3)
Treatment
without antidote
or hemodialysis
(n = 6)
Treatment with
antidote and
hemodialysis
(n = 12)
Treatment with
antidote and no
hemodialysis
(n = 7)
Antidote = intravenous ethanol or fomepizole
Fig. 1. Study flow diagram and treatment record.
excluded because the inhalant used by this patient did not
contain methanol by history and the serum methanol concentration was negative. Ten patients were included who did not
have a serum methanol concentration measured on admission. The inhalation of carburetor cleaning fluid containing
methanol was confirmed by history in the 68 admissions.
Sixteen patients were admitted 68 times for methanol
toxicity from the inhalation of carburetor cleaning fluid containing methanol (Table 1). All 16 patients were men, and 11
patients (69%) were Native Americans. The mean age at first
admission during this time period was 38 years (SD 9, range
22–49). The mean number of admissions per patient was four
(SD 3, range 1–12). Native American patients accounted for
more admissions per patient compared with non-Native
American patients (chi-square, p < 0.0001).
In 21 of the 68 cases, patients reported specific visual complaints; in 20 of the 68 cases, patients specifically denied any
visual complaints; and in the remaining 27 of 68 cases,
patients were “intoxicated” or a review of systems was
“unobtainable” because of their altered mental status.
Although none of the patients received a formal ophthalmology exam, all visual symptoms resolved before discharge
regardless of the severity of methanol toxicity or treatment
received.
Sixty-five cases presented with nausea and vomiting.
Only 3 of the 68 cases denied nausea and vomiting on
presentation.
The laboratory values obtained on admission are shown in
Table 2. Most patients presented with pH <7.35 (92%), serum
bicarbonate <20 mEq/L (96%), osmolal gap ≥10 mOsm/L
(81%), and anion gap >16 (69%). Measured serum methanol
levels were obtained in only 58 of the 68 admissions (85%).
Of these 58 admissions, 10 cases (17%) had an initial serum
methanol level <20 mg/dL, 29 cases (50%) between 20 and
49 mg/dL, and 19 cases (33%) had an initial serum methanol
level ≥50 mg/dL. Only six patients (9%) presented with a
measurable serum ethanol level. Serum formic acid levels
were not measured.
Clinical Toxicology vol. 47 no. 3 2009
Methanol toxicity secondary to inhalant abuse
241
Table 1. Patient demographics
Number of patients
16
Gender
Age at first admission, years (mean (SD))
Race
Men
Native American
Caucasian
Hispanic
Unknown
Number of admissions
Native American
Non-Native American
Number of admissions per patient
(mean (SD))
Native American
Non-Native American
16 (100%)
38 (9), range 22–49
11 (69%)
3 (19%)
1 (6%)
1 (6%)
68
61 (90%)*
7 (10%)
4 (4), range 1–12
6 (4), range 1–12
1 (1), range 1–3
Downloaded By: [Wallace, Erik A.] At: 15:00 13 April 2009
*Chi-square, p < 0.0001.
Table 2. Laboratory values on admission
HCO−3 (mEq/L)
Anion gap
Osmolal gap
(mOsm/L)
Serum methanol
(mg/dL)
Serum ethanol
(mg/dL)
All patients (n = 68)
Mean (SD)
7.23 (0.11)
Range
6.95–7.47
10 (5)
2–25
21 (7)
9–42
25 (17)
0–62
48 (33)
0–164
8 (32)
0–189
Serum methanol <20 mg/dL (n = 10)
Mean (SD)
7.32 (0.10)
Range
7.18–7.47
13 (5)
9–25
19 (8)
11–36
7 (6)
0–15
9 (5)
0–16
0
0
Serum methanol ³20 and<50 mg/dL (n = 29)
Mean (SD)
7.23 (0.09)
10 (5)
Range
6.95–7.39
4–21
20 (7)
9–39
19 (10)
19–38
35 (8)
21–49
14 (43)
0–189
Serum methanol ³ 50 mg/dL (n = 19)
Mean (SD)
7.20 (0.10)
Range
7.02–7.33
24 (7)
15–42
44 (11)
27–62
86 (28)
56–164
5 (20)
0–85
pH
8 (4)
2–15
Forty-six admissions (68%) were to the medical intensive care unit. All patients were treated with intravenous
fluids and bicarbonate. Of the 29 patients who presented
with a serum methanol level between 20 and 49 mg/dL,
20 patients (69%) were treated with an intravenous antidote (ethanol or fomepizole) and three patients (10%)
received an antidote and hemodialysis. Six patients (21%)
did not receive treatment with intravenous ethanol, fomepizole, or hemodialysis (Fig. 1). All 19 patients who presented with a serum methanol level ≥50 mg/dL received
intravenous ethanol or fomepizole; however, seven
patients (37%) did not receive hemodialysis. No patients
received folic acid or folinic acid. All patients survived
without permanent sequelae.
Discussion
Although inhalation abuse among adults is uncommon, we
identified methanol toxicity from inhalation of carburetor
cleaning fluid as a recurrent problem among the Native
American adult men studied. Sixty-nine percent of the
patients admitted with methanol toxicity from inhaling
carburetor cleaning fluid fumes were Native Americans;
however, they accounted for 90% of the admissions with
an average of six admissions per patient. In addition, the
average patient age in this population is higher than previously reported (Table 3) with initial laboratory values on
Table 3. Comparison of patient demographics with other case series
Study
McCormick et al. (8)
Frenia and Schauben (9)
LoVecchio et al. (10)
Bebarta et al. (11)
Wallace et al. (12)
Patients Cases
1
4
22
7
16
1
7
22
7
68
Men
Mean age,
years (range)
100%
100%
72.7%
95.7%
100%
17.0
27.6 (26–29)
17.0 (14–41)
29.0 (15–58)
38.4 (22–49)
Clinical Toxicology vol. 47 no. 3 2009
Downloaded By: [Wallace, Erik A.] At: 15:00 13 April 2009
242
E.A. Wallace and A.S. Green
admission that were similar to previous reports.8–11
Although inhalant use by race is well described in adolescents,2 data on inhalant use by race in adults are not available. In addition, lifetime inhalant abuse among Native
American adolescents is unknown as use by race is only
provided for white, black, and Hispanic adolescents.2
We believe that the increased age of these patients is significant since it is unlikely that their substance abuse
started late in life.
Treatment recommendations for methanol toxicity
include intravenous sodium bicarbonate and folic or folinic acid. Guidelines indicate that an antidote, preferably
fomepizole (rather than ethanol) should be given when
the serum methanol concentration is ≥20 mg/dL. Hemodialysis along with an antidote should be initiated when
the serum methanol concentration is ≥50 mg/dL.6,7 Previous
reports on inhalational methanol toxicity describe outcomes ranging from benign to more serious sequelae
including death5,8–11,13 Other authors have suggested that
lower levels of serum methanol are achieved through
inhalation versus ingestion, thus resulting in lower rates
of complications.10,11 However, serum methanol levels
≥50 mg/dL were seen in 19 admissions (28%). No permanent sequelae were observed in these patients despite the
fact that seven patients did not receive hemodialysis,
which was indicated according to current treatment guidelines.6,7
Because ethanol has a higher affinity for alcohol dehydrogenase than methanol, concurrent abuse of ethanol can
delay methanol metabolism into formic acid and subsequent complications of metabolic acidosis. Only 6 out of
68 cases had measurable serum ethanol levels with no difference in outcomes. It is difficult to identify the timeline
between the patient’s ingestion/inhalation and their presentation to a health-care facility.14 Although the clinical
course between inhalation and ingestion of methanol may
differ, current guidelines do not differ between treating
these two groups of patients. It is also not known whether
pharmacogentics affects morbidity and mortality from
methanol toxicity.
Limitations
Our retrospective chart review has several limitations.
Medical records are often incomplete so historical and physical data may have been missing. Data regarding methanol
concentration of carburetor cleaning fluids and the quantity
of each product inhaled to produce a given methanol level
were unavailable. Similarly, the time between inhalation of
the carburetor cleaning fluid fumes and admission could not
be determined.
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Conclusion
Methanol toxicity from inhalation of carburetor cleaning
fluid is a recurrent problem among some Native American
men. These patients are older than those reported previously,
and this represents a patient group in whom the suspicion of
methanol ingestion must be entertained when the patient presents with an unexplained metabolic acidosis. Although
many clinicians question patients about oral ingestion of
methanol, we believe that the suspicion for inhalation of
methanol should be high in older Native American men.
Future research is needed to determine which factors lead to
recurrent inhalant abuse among adults.
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