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...
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
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.
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...
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
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.
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...
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