A series of ureido derivatives of pyridine (UDPs) were developed as inducers of leukemic cell dif... more A series of ureido derivatives of pyridine (UDPs) were developed as inducers of leukemic cell differentiation. Fifteen agents prepared by coupling aminopyridines with appropriate isocyanates were structurally identified and tested for both antiproliferative and differentiation inducing activity in cultures of murine and human leukemic cells. Five of these lipophilic compounds [2-(3-ethylureido)-pyridine (1), 2-(3-ethylureido)-6-methylpyridine (4), 2,6-bis-(3-ethylureido)-pyridine (7), 2-(3-ethylureido)-5-methylpyridine (14) and 2-(3-ethylureido)-4,5-dimethylpyridine (15)], promoted terminal erythroid maturation of murine erythroleukemia cells (MEL) (95% hemoglobin producing cells) and stimulated hemoglobin synthesis at concentrations as low as 0.075-0.5 mM. These concentrations are 50-70 fold lower than the optimum inducing concentration of hexamethylene bisacetamide (HMBA), a potent known inducer of differentiation. The proportion of cells induced by each ureido derivative of pyrid...
Enalapril is a prodrug that is metabolized to its main active metabolite, enalaprilat that is a p... more Enalapril is a prodrug that is metabolized to its main active metabolite, enalaprilat that is a potent inhibitor of angiotensin converting enzyme (ACE). A simple, rapid, sensitive, precise and accurate SIM GC-MS method, using solid-phase extraction and derivatization with methyl iodide, for the quantitative determination of enalapril and enalaprilat in human plasma was developed and validated. The ions at m/z 220 for enalapril, m/z 234 for enalaprilat and m/z 172 for internal standard, perindopril, were monitored. The calibration graphs for the analytes were linear in the 5-160 ng mL-1 concentration range (r > 0.999). Intra-day and inter-day precision for enalapril ranged from 2.4 to 3.5 and 3.9 to 7.9%, and for enalaprilat from 5.3 to 7.8 and 6.7 to 9.1%. Accuracy was better than 105.5% for both enalapril and enalaprilat. The method was sensitive with a lower limit of quantitation (LLOQ) of 2 ng mL-1 for both analytes and was not interfered by other plasma components. The method was applied for the determination of enalaprilat in a pharmacokinetic study after single oral administration of 20 mg enalapril to 24 healthy subjects.
The uptake of flumequine by Artemia nauplii was studied as a function of its concentration in the... more The uptake of flumequine by Artemia nauplii was studied as a function of its concentration in the enrichment medium and of the duration of the enrichment period. An emulsion containing 20, 30, 40 or 50% (w/w) flumequine was administered to nauplii for 4, 8, 12, 24 or 32 h. Increased uptake of flumequine (450.4 ±15.8 μg/g dry weight) and good survival rates of the nauplii were observed with the 40% emulsion and 24 h enrichment. The concentration data of flumequine in nauplii were best fit to a two phase exponential elimination model with the first phase elimination half-life (t 1/2α) and the terminal phase elimination half-life (t 1/2β) to be 1 and 19.5 h, respectively. In the efficacy trial 1000 sea bass larvae were challenged by bath with Listonella anguillarum strain 332A, 2.5 × 10 7 CFU/ml for 1 h. Fish either received no treatment or oral treatment with flumequine bioencapsulated in nauplii or bath treatments with flumequine. Medication commenced two days following challenge, for bath treatments performed on day 2, 4 and 6 post challenge at a dosage of 20 mg/l for 2 h. Medication for oral treatments, commenced two days post challenge and two doses each of 700 nauplii per fish daily for five consecutive days. Cumulative mortality reached 96% for the unmedicated challenged group, 43% in the group receiving bath treatments and 29% in the group receiving medicated nauplii. Pharmacokinetic parameters of flumequine were calculated in sea bass larvae, after bath treatment with flumequine and oral treatment with flumequine bioencapsulated in nauplii. Steady state concentrations of flumequine (80.7 μg/g) in sea bass larvae were achieved after a 5-day oral treatment with medicated nauplii and the elimination half-life was found to be 19.5 h.
The pharmacokinetics of trimethoprim TMP , sulfamethoxazole SMX and its metabolite Ž. N-acetyl-su... more The pharmacokinetics of trimethoprim TMP , sulfamethoxazole SMX and its metabolite Ž. N-acetyl-sulfamethoxazole N-acetyl-SMX , were studied in Artemia nauplii as a function of the duration and temperature of their storage, following their enrichment with the therapeutics using the bioencapsulation technique. A marked decrease in the therapeutic content of the nauplii was observed upon storage at 188C and 258C and it was concluded that medicated nauplii should either be administered fresh to fish larvae or after storage for 8 h at 58C, at the most. Under the latter conditions, satisfactory levels of TMP and SMX were achieved, high survival rates and dry weight contents of the nauplii were preserved and minimal leakage of the therapeutics to the environment was secured. Treatment of seabass larvae with one, three, six or ten doses of medicated Artemia nauplii, showed that maximum levels of the therapeutics are achieved in fish larvae when 10 doses are used. Following the treatment scheme of oral administration of 10 doses of medicated Artemia nauplii to fish larvae, the residual kinetics of TMP, SMX and N-acetyl-sulfamethoxazole were studied in seabass larvae. TMP and SMX showed different kinetic characteristics. A steady state of SMX concentration is considered to be achieved in fish body tissue during the 5-day medication period. TMP, SMX as well as the metabolite N-acetyl-sulfamethoxazole, were detectable in small amounts in fish body tissue even 100 h-post treatment. These data suggest that oral medication of fish larvae through the use of Artemia nauplii as a carrier of therapeutics, appears to be a quite promising approach to be used as an alternative method of treatment, which
ABSTRACT Introduction. Herbal medicinal products (HMPs) are capable of modulating the metabolism ... more ABSTRACT Introduction. Herbal medicinal products (HMPs) are capable of modulating the metabolism through CYPs of several drugs. Horse chestnut seed extract (HCSE) derived from Aesculus hippocastanum has been found to inhibit CYP3A4 activity (Hellum and Nilsen, 2008). The aim of this study was to investigate two of the constituents of HCSE, aescin and aesculetin, for their in vitro inhibitory potential of CYP3A4 and CYP2D6. Aescin is the pharmacologically active compound of the herb and aescin is a secondary compound without attributed therapeutic properties. Methods. Dextromethorphan was used as a probe drug to simultaneously assess CYP3A4 and CYP2D6 activity. Incubations of recombinant CYPs and analysis of the formed metabolites, 3-methoxymorphinan trough CYP3A4 and dextrorphan through CYP2D6, were conducted as previously described using a validated SIM GC/MS method (Spanakis et al., 2009). Results: The mean basic control activity of dextromethorphan metabolism was estimated to be 820 ? 58 pmol/CYP pmol/min for CYP3A4 and 75.5 ? 3.7 pmol/CYP pmol/min for CYP2D6. The estimated IC50 values for aescin were 12.1 ? 1.6 ?? for CYP3A4 and 24.3 ? 5.3 ?? for CYP2D6 and for aesculetin were 6.18 ? 1.3 ?? for CYP3A4 and 39.2 ? 5.7 ?? for CYP2D6, respectively. Conclusion. The results of the present study showed that aesculetin is a more potent inhibitor of CYP3A4 than aescin suggesting that it may also contribute to the previously observed CYP3A4 inhibitory effect found for HCSE. Moreover, both compounds showed to be inhibitors of CYP2D6. 0
Nanomedicine: Nanotechnology, Biology and Medicine, 2014
Zeolite particles with different pore diameter and particle size were loaded with the model antic... more Zeolite particles with different pore diameter and particle size were loaded with the model anticancer drug 5-fluorouracil. The loaded zeolites were characterized by means of SEM, XRD, DSC, XPS, N 2 physisorption and FT-IR. Higher loading of 5-FU was observed for NaX-FAU than BEA. Release studies were carried out in simulated gastric fluid. Release of 5-FU from NaX-FAU showed exponential-type behaviour with the drug fully released within 10 min. In the case of BEA, the kinetics of 5-FU shows a multi-step profile with prolonged release over time. Molecular dynamics simulations showed that diffusion of the drug molecule through the BEA framework is lower than for NaX-FAU due to increased van der Waals interaction between the drug and the framework. The effect of zeolitic particles on the viability of Caco-2 monolayers showed that the NaX-FAU particles cause a reduction of cell viability in a more pronounced way compared with the BEA particles.
ABSTRACT Nowadays, it is of great importance for pharmacology to predict drug response by applyin... more ABSTRACT Nowadays, it is of great importance for pharmacology to predict drug response by applying validated assays, either early in new drug development process, or in the clinical settings. In an effort to establish an infrastructure in our laboratory to clinically assess drug interactions, we were able to confirm that herbal medicinal products of horse chestnut seed extracts (HCSE) inhibit drug metabolizing enzymes CYP3A4 and CYP2D6 in vitro. In this work, we applied the Caco-2 cell model system used in drug absorption studies to further investigate the pharmacological relevance of these observations. In particular, we evaluated the effect of HCSE and its constituent aescin in Caco-2 cells by assessing: a) The viability of cells through the application of MTT assay; b) The cellular integrity of membranes by measuring transepithelial electric resistance (TEER); and c) The adherent junctions’ morphology. The data obtained thus far indicate that HCSE and aescin: 1) Do not significantly affect cell viability; 2) Alter cellular integrity as seen by TEER values; Interestingly, TEER exhibited an initial significant reduction within the first 3hr of treatment that subsequently has been reversed leading thereafter to a substantial increase by 24hr; and 3) Modulate E-cadherin levels at cellular junctions. Overall, these data propose that the potential alteration of cell membrane integrity by HCSE and aescin could affect the paracellular drug transport in the intestine, although such a conclusion needs further pharmacological and clinical investigation.
Atenolol is a cardioselective b1-adrenergic blocker widely used for the treatment of hypertension... more Atenolol is a cardioselective b1-adrenergic blocker widely used for the treatment of hypertension, angina pectoris and cardiac arrhythmias. A simple, specific, sensitive, precise and accurate high-performance liquid chromatography method with fluorescence detection has been developed and validated for the determination of atenolol in human plasma. After addition of the internal standard, the analytes were extracted by liquid-liquid extraction. The calibration graph for atenolol was linear in a 10-1,000 ng/mL concentration range (r > 0.999), using 0.5-mL plasma samples. The assay precision of the method was less than 6.4%, the assay accuracy ranged between 99.6% and 101.6%, and the absolute recovery of atenolol and internal standard was better than 66.1% and 76.2%, respectively. The method was found to be suitable for the quantification of atenolol in a pharmacokinetic study after a single oral administration of 100 mg atenolol to 18 healthy subjects.
Dextromethorphan is used as a probe drug for assessing CYP2D6 and CYP3A4 activity in vivo and in ... more Dextromethorphan is used as a probe drug for assessing CYP2D6 and CYP3A4 activity in vivo and in vitro. A SIM GC/MS method without derivatization for the simultaneous determination of dextromethorphan and its metabolites, dextrorphan, 3-methoxymorphinan and 3-hydroxymorphinan, in human plasma, urine and in vitro incubation matrix was developed and validated. Calibration curves indicated good linearity with a coefficient of variation (r) better than 0.995. The lower limit of quantitation was found to be 10 ng/mL for all analytes in all matrices. Intra-day and inter-day precision for dextromethorphan and its metabolites was better than 9.02 and 9.91%, respectively and accuracy ranged between 91.76 and 106.27%. Recovery for dextromethorphan, its metabolites and internal standard levallorphan was greater than 72.68%. The method has been successfully applied for the in vitro inhibition of metabolism of dextromethorphan by CYP2D6 and CYP3A4 using known inhibitors of CYPs such as quinidine and verapamil.
The study investigates the potential interaction of the herbal medicinal product of Rhodiola rose... more The study investigates the potential interaction of the herbal medicinal product of Rhodiola rosea on the pharmacokinetics of losartan and its active metabolite EXP3174 after concurrent oral administration to rabbits. We conducted a randomized, single-dose, two-treatment, two-period, two-sequence, cross-over pharmacokinetic study on 6 healthy female New Zealand rabbits, after concurrent oral administration of losartan (5 mg/kg) and the herbal medicinal product of R. rosea (50 mg/kg). Quantification of losartan and its main active metabolite EXP3174 was achieved using a validated HPCL/UV method. Pharmacokinetic and statistical analysis was performed using the EquivTest/PK software. Administration of the herbal medicinal product of R. rosea resulted in a statistically significant increase of the following pharmacokinetic parameters for losartan: the maximum plasma concentration (C(max)), the area under the curve (AUC) and the apparent total body clearance (CL/F). An almost 2-fold increase in the AUC of losartan was observed after concurrent administration of the herbal medicinal product of R. rosea. No statistically significant alteration was observed in the pharmacokinetic parameters of the active metabolite of losartan EXP3174. The data of this study suggest that R. rosea significantly alters the pharmacokinetic properties of losartan after concurrent oral administration to rabbits. A study in humans should be conducted to assess the clinical significance of a possible herb-drug interaction between the herbal medicinal products of R. rosea and drugs such as losartan, which are substrates of both CYPs and P-gp.
International journal of clinical pharmacology and therapeutics, 2005
To determine the CYP2D6 phenotype in a Greek population by using dextromethorphan (DM) as a probe... more To determine the CYP2D6 phenotype in a Greek population by using dextromethorphan (DM) as a probe drug. DM (30 mg) was given orally to 102 unrelated Greek subjects and 8-hour urine samples were collected. Concentrations of DM and its metabolite dextrorphan (DX) were determined using a validated HPLC assay. Metabolic molar ratio (MR) of DM to free DX in log form was used as an in vivo index of metabolic status. The frequency distribution histogram of MR was bimodal. An antimode of 0.25 for the mean log MR was determined using probit analysis. Seven of 102 subjects (6.9%) were poor metabolizers (PMs). The PM frequency of CYP2D6 in Greek subjects was similar to other Caucasian populations.
International journal of clinical pharmacology and therapeutics, 2003
To compare the relative bioavailability and bioequivalence of 2 enalapril tablet formulations in ... more To compare the relative bioavailability and bioequivalence of 2 enalapril tablet formulations in healthy volunteers under fasting conditions. An open-label, single-dose, randomized, two-period, crossover trial with a 1-week washout period in 24 healthy volunteers. The 2 enalapril 20 mg tablet formulations used were Antiprex (Elpen, Greece) as test and Renitec (Vianex, Greece) as reference preparation. Serial blood samples were collected at 19 points for 36 h. Plasma samples were analyzed for enalaprilat, the pharmacologically active metabolite of enalapril, by a validated GC/MS assay. Pharmacokinetic parameters, such as AUC(0-infinity), AUC(0-t), C(max) T(max), t1/2 and MRT were calculated from plasma concentrations for both formulations. Statistical comparisons (ANOVA and 90% confidence intervals) of AUC(0-infinity), AUC(0-t) and C(max) data were evaluated after logarithmic transformation, and differences of T(max) were tested non-parametrically. The parametric 90% confidence inter...
International journal of clinical pharmacology and therapeutics, 2000
To assess the bioequivalence of two oral formulations containing 10 mg of nifedipine. The test pr... more To assess the bioequivalence of two oral formulations containing 10 mg of nifedipine. The test preparation were Macorel tablets, the reference preparation were Adalat tablets. The study was designed as a single-dose, three-period crossover randomized design to 18 non-smoker, healthy male volunteers under fasting conditions. Seventeen volunteers completed the study. Plasma samples were analyzed for nifedipine by HPLC after solid-phase extraction. The pharmacokinetic parameters used to assess the bioequivalence of the two formulations were AUC(0-infinite) and AUC(0-t) for the extent of absorption and Cmax and Tmax for the rate of absorption. Statistical comparisons of AUC(0-infinite) AUC(0-t), and Cmax data were evaluated after logarithmic transformation by two-way analysis of variance (ANOVA), and differences of Tmax were tested non-parametricaly. Point estimates (90% confidence intervals) of the test/reference ratios were 97.4% (87.6%-108.3%) for AUC(0-infinite) 97.0% (85.6%-110.1%)...
Methods and Findings in Experimental and Clinical Pharmacology, 1999
We conducted an open-label pilot study of dextromethorphan (DM) in intractable partial epilepsy w... more We conducted an open-label pilot study of dextromethorphan (DM) in intractable partial epilepsy with the following objectives: a preliminary evaluation of the drug's safety and efficacy in the epileptic patient and a definition of a concentration range which can be safely achieved in future studies. Sixteen patients with drug-resistant, localization-related epilepsies entered the trial. After an 8-week baseline period, DM was added to the existing antiepileptic drugs at a dose of 40 and 50 mg every 6 h (160 and 200 mg/day). Each treatment period lasted 8 weeks. Seizure control improved after administration of DM, especially in the group of intermediate and slow metabolizers. Two patients, however, experienced increased seizure frequency and withdrew from the study. Adverse effects during DM administration were mild and transient. DM was well tolerated even in patients with high plasma levels of the drug (up to 15020 ng/dl). Our results indicate that DM is safe and effective in t...
A series of ureido derivatives of pyridine (UDPs) were developed as inducers of leukemic cell dif... more A series of ureido derivatives of pyridine (UDPs) were developed as inducers of leukemic cell differentiation. Fifteen agents prepared by coupling aminopyridines with appropriate isocyanates were structurally identified and tested for both antiproliferative and differentiation inducing activity in cultures of murine and human leukemic cells. Five of these lipophilic compounds [2-(3-ethylureido)-pyridine (1), 2-(3-ethylureido)-6-methylpyridine (4), 2,6-bis-(3-ethylureido)-pyridine (7), 2-(3-ethylureido)-5-methylpyridine (14) and 2-(3-ethylureido)-4,5-dimethylpyridine (15)], promoted terminal erythroid maturation of murine erythroleukemia cells (MEL) (95% hemoglobin producing cells) and stimulated hemoglobin synthesis at concentrations as low as 0.075-0.5 mM. These concentrations are 50-70 fold lower than the optimum inducing concentration of hexamethylene bisacetamide (HMBA), a potent known inducer of differentiation. The proportion of cells induced by each ureido derivative of pyrid...
Enalapril is a prodrug that is metabolized to its main active metabolite, enalaprilat that is a p... more Enalapril is a prodrug that is metabolized to its main active metabolite, enalaprilat that is a potent inhibitor of angiotensin converting enzyme (ACE). A simple, rapid, sensitive, precise and accurate SIM GC-MS method, using solid-phase extraction and derivatization with methyl iodide, for the quantitative determination of enalapril and enalaprilat in human plasma was developed and validated. The ions at m/z 220 for enalapril, m/z 234 for enalaprilat and m/z 172 for internal standard, perindopril, were monitored. The calibration graphs for the analytes were linear in the 5-160 ng mL-1 concentration range (r > 0.999). Intra-day and inter-day precision for enalapril ranged from 2.4 to 3.5 and 3.9 to 7.9%, and for enalaprilat from 5.3 to 7.8 and 6.7 to 9.1%. Accuracy was better than 105.5% for both enalapril and enalaprilat. The method was sensitive with a lower limit of quantitation (LLOQ) of 2 ng mL-1 for both analytes and was not interfered by other plasma components. The method was applied for the determination of enalaprilat in a pharmacokinetic study after single oral administration of 20 mg enalapril to 24 healthy subjects.
The uptake of flumequine by Artemia nauplii was studied as a function of its concentration in the... more The uptake of flumequine by Artemia nauplii was studied as a function of its concentration in the enrichment medium and of the duration of the enrichment period. An emulsion containing 20, 30, 40 or 50% (w/w) flumequine was administered to nauplii for 4, 8, 12, 24 or 32 h. Increased uptake of flumequine (450.4 ±15.8 μg/g dry weight) and good survival rates of the nauplii were observed with the 40% emulsion and 24 h enrichment. The concentration data of flumequine in nauplii were best fit to a two phase exponential elimination model with the first phase elimination half-life (t 1/2α) and the terminal phase elimination half-life (t 1/2β) to be 1 and 19.5 h, respectively. In the efficacy trial 1000 sea bass larvae were challenged by bath with Listonella anguillarum strain 332A, 2.5 × 10 7 CFU/ml for 1 h. Fish either received no treatment or oral treatment with flumequine bioencapsulated in nauplii or bath treatments with flumequine. Medication commenced two days following challenge, for bath treatments performed on day 2, 4 and 6 post challenge at a dosage of 20 mg/l for 2 h. Medication for oral treatments, commenced two days post challenge and two doses each of 700 nauplii per fish daily for five consecutive days. Cumulative mortality reached 96% for the unmedicated challenged group, 43% in the group receiving bath treatments and 29% in the group receiving medicated nauplii. Pharmacokinetic parameters of flumequine were calculated in sea bass larvae, after bath treatment with flumequine and oral treatment with flumequine bioencapsulated in nauplii. Steady state concentrations of flumequine (80.7 μg/g) in sea bass larvae were achieved after a 5-day oral treatment with medicated nauplii and the elimination half-life was found to be 19.5 h.
The pharmacokinetics of trimethoprim TMP , sulfamethoxazole SMX and its metabolite Ž. N-acetyl-su... more The pharmacokinetics of trimethoprim TMP , sulfamethoxazole SMX and its metabolite Ž. N-acetyl-sulfamethoxazole N-acetyl-SMX , were studied in Artemia nauplii as a function of the duration and temperature of their storage, following their enrichment with the therapeutics using the bioencapsulation technique. A marked decrease in the therapeutic content of the nauplii was observed upon storage at 188C and 258C and it was concluded that medicated nauplii should either be administered fresh to fish larvae or after storage for 8 h at 58C, at the most. Under the latter conditions, satisfactory levels of TMP and SMX were achieved, high survival rates and dry weight contents of the nauplii were preserved and minimal leakage of the therapeutics to the environment was secured. Treatment of seabass larvae with one, three, six or ten doses of medicated Artemia nauplii, showed that maximum levels of the therapeutics are achieved in fish larvae when 10 doses are used. Following the treatment scheme of oral administration of 10 doses of medicated Artemia nauplii to fish larvae, the residual kinetics of TMP, SMX and N-acetyl-sulfamethoxazole were studied in seabass larvae. TMP and SMX showed different kinetic characteristics. A steady state of SMX concentration is considered to be achieved in fish body tissue during the 5-day medication period. TMP, SMX as well as the metabolite N-acetyl-sulfamethoxazole, were detectable in small amounts in fish body tissue even 100 h-post treatment. These data suggest that oral medication of fish larvae through the use of Artemia nauplii as a carrier of therapeutics, appears to be a quite promising approach to be used as an alternative method of treatment, which
ABSTRACT Introduction. Herbal medicinal products (HMPs) are capable of modulating the metabolism ... more ABSTRACT Introduction. Herbal medicinal products (HMPs) are capable of modulating the metabolism through CYPs of several drugs. Horse chestnut seed extract (HCSE) derived from Aesculus hippocastanum has been found to inhibit CYP3A4 activity (Hellum and Nilsen, 2008). The aim of this study was to investigate two of the constituents of HCSE, aescin and aesculetin, for their in vitro inhibitory potential of CYP3A4 and CYP2D6. Aescin is the pharmacologically active compound of the herb and aescin is a secondary compound without attributed therapeutic properties. Methods. Dextromethorphan was used as a probe drug to simultaneously assess CYP3A4 and CYP2D6 activity. Incubations of recombinant CYPs and analysis of the formed metabolites, 3-methoxymorphinan trough CYP3A4 and dextrorphan through CYP2D6, were conducted as previously described using a validated SIM GC/MS method (Spanakis et al., 2009). Results: The mean basic control activity of dextromethorphan metabolism was estimated to be 820 ? 58 pmol/CYP pmol/min for CYP3A4 and 75.5 ? 3.7 pmol/CYP pmol/min for CYP2D6. The estimated IC50 values for aescin were 12.1 ? 1.6 ?? for CYP3A4 and 24.3 ? 5.3 ?? for CYP2D6 and for aesculetin were 6.18 ? 1.3 ?? for CYP3A4 and 39.2 ? 5.7 ?? for CYP2D6, respectively. Conclusion. The results of the present study showed that aesculetin is a more potent inhibitor of CYP3A4 than aescin suggesting that it may also contribute to the previously observed CYP3A4 inhibitory effect found for HCSE. Moreover, both compounds showed to be inhibitors of CYP2D6. 0
Nanomedicine: Nanotechnology, Biology and Medicine, 2014
Zeolite particles with different pore diameter and particle size were loaded with the model antic... more Zeolite particles with different pore diameter and particle size were loaded with the model anticancer drug 5-fluorouracil. The loaded zeolites were characterized by means of SEM, XRD, DSC, XPS, N 2 physisorption and FT-IR. Higher loading of 5-FU was observed for NaX-FAU than BEA. Release studies were carried out in simulated gastric fluid. Release of 5-FU from NaX-FAU showed exponential-type behaviour with the drug fully released within 10 min. In the case of BEA, the kinetics of 5-FU shows a multi-step profile with prolonged release over time. Molecular dynamics simulations showed that diffusion of the drug molecule through the BEA framework is lower than for NaX-FAU due to increased van der Waals interaction between the drug and the framework. The effect of zeolitic particles on the viability of Caco-2 monolayers showed that the NaX-FAU particles cause a reduction of cell viability in a more pronounced way compared with the BEA particles.
ABSTRACT Nowadays, it is of great importance for pharmacology to predict drug response by applyin... more ABSTRACT Nowadays, it is of great importance for pharmacology to predict drug response by applying validated assays, either early in new drug development process, or in the clinical settings. In an effort to establish an infrastructure in our laboratory to clinically assess drug interactions, we were able to confirm that herbal medicinal products of horse chestnut seed extracts (HCSE) inhibit drug metabolizing enzymes CYP3A4 and CYP2D6 in vitro. In this work, we applied the Caco-2 cell model system used in drug absorption studies to further investigate the pharmacological relevance of these observations. In particular, we evaluated the effect of HCSE and its constituent aescin in Caco-2 cells by assessing: a) The viability of cells through the application of MTT assay; b) The cellular integrity of membranes by measuring transepithelial electric resistance (TEER); and c) The adherent junctions’ morphology. The data obtained thus far indicate that HCSE and aescin: 1) Do not significantly affect cell viability; 2) Alter cellular integrity as seen by TEER values; Interestingly, TEER exhibited an initial significant reduction within the first 3hr of treatment that subsequently has been reversed leading thereafter to a substantial increase by 24hr; and 3) Modulate E-cadherin levels at cellular junctions. Overall, these data propose that the potential alteration of cell membrane integrity by HCSE and aescin could affect the paracellular drug transport in the intestine, although such a conclusion needs further pharmacological and clinical investigation.
Atenolol is a cardioselective b1-adrenergic blocker widely used for the treatment of hypertension... more Atenolol is a cardioselective b1-adrenergic blocker widely used for the treatment of hypertension, angina pectoris and cardiac arrhythmias. A simple, specific, sensitive, precise and accurate high-performance liquid chromatography method with fluorescence detection has been developed and validated for the determination of atenolol in human plasma. After addition of the internal standard, the analytes were extracted by liquid-liquid extraction. The calibration graph for atenolol was linear in a 10-1,000 ng/mL concentration range (r > 0.999), using 0.5-mL plasma samples. The assay precision of the method was less than 6.4%, the assay accuracy ranged between 99.6% and 101.6%, and the absolute recovery of atenolol and internal standard was better than 66.1% and 76.2%, respectively. The method was found to be suitable for the quantification of atenolol in a pharmacokinetic study after a single oral administration of 100 mg atenolol to 18 healthy subjects.
Dextromethorphan is used as a probe drug for assessing CYP2D6 and CYP3A4 activity in vivo and in ... more Dextromethorphan is used as a probe drug for assessing CYP2D6 and CYP3A4 activity in vivo and in vitro. A SIM GC/MS method without derivatization for the simultaneous determination of dextromethorphan and its metabolites, dextrorphan, 3-methoxymorphinan and 3-hydroxymorphinan, in human plasma, urine and in vitro incubation matrix was developed and validated. Calibration curves indicated good linearity with a coefficient of variation (r) better than 0.995. The lower limit of quantitation was found to be 10 ng/mL for all analytes in all matrices. Intra-day and inter-day precision for dextromethorphan and its metabolites was better than 9.02 and 9.91%, respectively and accuracy ranged between 91.76 and 106.27%. Recovery for dextromethorphan, its metabolites and internal standard levallorphan was greater than 72.68%. The method has been successfully applied for the in vitro inhibition of metabolism of dextromethorphan by CYP2D6 and CYP3A4 using known inhibitors of CYPs such as quinidine and verapamil.
The study investigates the potential interaction of the herbal medicinal product of Rhodiola rose... more The study investigates the potential interaction of the herbal medicinal product of Rhodiola rosea on the pharmacokinetics of losartan and its active metabolite EXP3174 after concurrent oral administration to rabbits. We conducted a randomized, single-dose, two-treatment, two-period, two-sequence, cross-over pharmacokinetic study on 6 healthy female New Zealand rabbits, after concurrent oral administration of losartan (5 mg/kg) and the herbal medicinal product of R. rosea (50 mg/kg). Quantification of losartan and its main active metabolite EXP3174 was achieved using a validated HPCL/UV method. Pharmacokinetic and statistical analysis was performed using the EquivTest/PK software. Administration of the herbal medicinal product of R. rosea resulted in a statistically significant increase of the following pharmacokinetic parameters for losartan: the maximum plasma concentration (C(max)), the area under the curve (AUC) and the apparent total body clearance (CL/F). An almost 2-fold increase in the AUC of losartan was observed after concurrent administration of the herbal medicinal product of R. rosea. No statistically significant alteration was observed in the pharmacokinetic parameters of the active metabolite of losartan EXP3174. The data of this study suggest that R. rosea significantly alters the pharmacokinetic properties of losartan after concurrent oral administration to rabbits. A study in humans should be conducted to assess the clinical significance of a possible herb-drug interaction between the herbal medicinal products of R. rosea and drugs such as losartan, which are substrates of both CYPs and P-gp.
International journal of clinical pharmacology and therapeutics, 2005
To determine the CYP2D6 phenotype in a Greek population by using dextromethorphan (DM) as a probe... more To determine the CYP2D6 phenotype in a Greek population by using dextromethorphan (DM) as a probe drug. DM (30 mg) was given orally to 102 unrelated Greek subjects and 8-hour urine samples were collected. Concentrations of DM and its metabolite dextrorphan (DX) were determined using a validated HPLC assay. Metabolic molar ratio (MR) of DM to free DX in log form was used as an in vivo index of metabolic status. The frequency distribution histogram of MR was bimodal. An antimode of 0.25 for the mean log MR was determined using probit analysis. Seven of 102 subjects (6.9%) were poor metabolizers (PMs). The PM frequency of CYP2D6 in Greek subjects was similar to other Caucasian populations.
International journal of clinical pharmacology and therapeutics, 2003
To compare the relative bioavailability and bioequivalence of 2 enalapril tablet formulations in ... more To compare the relative bioavailability and bioequivalence of 2 enalapril tablet formulations in healthy volunteers under fasting conditions. An open-label, single-dose, randomized, two-period, crossover trial with a 1-week washout period in 24 healthy volunteers. The 2 enalapril 20 mg tablet formulations used were Antiprex (Elpen, Greece) as test and Renitec (Vianex, Greece) as reference preparation. Serial blood samples were collected at 19 points for 36 h. Plasma samples were analyzed for enalaprilat, the pharmacologically active metabolite of enalapril, by a validated GC/MS assay. Pharmacokinetic parameters, such as AUC(0-infinity), AUC(0-t), C(max) T(max), t1/2 and MRT were calculated from plasma concentrations for both formulations. Statistical comparisons (ANOVA and 90% confidence intervals) of AUC(0-infinity), AUC(0-t) and C(max) data were evaluated after logarithmic transformation, and differences of T(max) were tested non-parametrically. The parametric 90% confidence inter...
International journal of clinical pharmacology and therapeutics, 2000
To assess the bioequivalence of two oral formulations containing 10 mg of nifedipine. The test pr... more To assess the bioequivalence of two oral formulations containing 10 mg of nifedipine. The test preparation were Macorel tablets, the reference preparation were Adalat tablets. The study was designed as a single-dose, three-period crossover randomized design to 18 non-smoker, healthy male volunteers under fasting conditions. Seventeen volunteers completed the study. Plasma samples were analyzed for nifedipine by HPLC after solid-phase extraction. The pharmacokinetic parameters used to assess the bioequivalence of the two formulations were AUC(0-infinite) and AUC(0-t) for the extent of absorption and Cmax and Tmax for the rate of absorption. Statistical comparisons of AUC(0-infinite) AUC(0-t), and Cmax data were evaluated after logarithmic transformation by two-way analysis of variance (ANOVA), and differences of Tmax were tested non-parametricaly. Point estimates (90% confidence intervals) of the test/reference ratios were 97.4% (87.6%-108.3%) for AUC(0-infinite) 97.0% (85.6%-110.1%)...
Methods and Findings in Experimental and Clinical Pharmacology, 1999
We conducted an open-label pilot study of dextromethorphan (DM) in intractable partial epilepsy w... more We conducted an open-label pilot study of dextromethorphan (DM) in intractable partial epilepsy with the following objectives: a preliminary evaluation of the drug's safety and efficacy in the epileptic patient and a definition of a concentration range which can be safely achieved in future studies. Sixteen patients with drug-resistant, localization-related epilepsies entered the trial. After an 8-week baseline period, DM was added to the existing antiepileptic drugs at a dose of 40 and 50 mg every 6 h (160 and 200 mg/day). Each treatment period lasted 8 weeks. Seizure control improved after administration of DM, especially in the group of intermediate and slow metabolizers. Two patients, however, experienced increased seizure frequency and withdrew from the study. Adverse effects during DM administration were mild and transient. DM was well tolerated even in patients with high plasma levels of the drug (up to 15020 ng/dl). Our results indicate that DM is safe and effective in t...
Uploads
Papers by I. Niopas