Jan Juřica

Cannabinoids and Cytochrome P450 Interactions

OBJECTIVE This review consists of three parts, representing three different possibilities of interactions between cannabinoid receptor ligands of both exogenous and endogenous origin and cytochrome P450 enzymes (CYPs). The first part deals with cannabinoids as CYP substrates, the second summarizes current knowledge on the influence of various cannabinoids on the metabolic activity of CYP, and the third outline a possible involvement of the endocannabinoid system and cannabinoid ligands in the regulation of CYP liver activity. METHODS We performed a structured search of bibliographic and drug databases for peer-reviewed literature using focused review questions. RESULTS Biotransformation via a hydrolytic pathway is the major route of endocannabinoid metabolism and the deactivation of substrates is characteristic, in contrast to the minor oxidative pathway via CYP involved in the bioactivation reactions. Phytocannabinoids are extensively metabolized by CYPs. The enzymes CYP2C9, CYP2C19, and CYP3A4 catalyze most of their hydroxylations. Similarly, CYP represents a major metabolic pathway for both synthetic cannabinoids used therapeutically and drugs that are abused. In vitro experiments document the mostly CYP inhibitory activity of the major phytocannabinoids, with cannabidiol as the most potent inhibitor of many CYPs. The drug-drug interactions between cannabinoids and various drugs at the CYP level are reported, but their clinical relevance remains unclear. The direct activation/inhibition of nuclear receptors in the liver cells by cannabinoids may result in a change of CYP expression and activity. Finally, we hypothesize the interplay of central cannabinoid receptors with numerous nervous systems, resulting in a hormone-mediated signal towards nuclear receptors in hepatocytes.

Simultaneous HPLC determination of tolbutamide, phenacetin and their metabolites as markers of cytochromes 1A2 and 2C6/11 in rat liver perfusate.

A new, simple, rapid, sensitive, and repeatable reversed-phase HPLC method was developed and validated for the simultaneous determination of tolbutamide, phenacetin and their metabolites in rat liver perfusate. Chlorpropamide was used as an internal standard to ensure the precision and accuracy of this method. Analytes were extracted into diethyl ether using a two-step liquid-liquid extraction. A C18 analytical column and a mobile phase composed of acetonitrile and potassium phosphate buffer were used for the chromatographic separation with UV detection. Limits of detection varied between 20 and 46ng/mL for phenacetin, tolbutamide and their metabolites. The overall extraction recovery for the analytes varied from 65.4% in paracetamol to 88.0% in tolbutamide for concentrations within the expected range of concentrations from previous experimental samples. In terms of precision, the intra- and inter-day variation at three different concentrations in all analytes never exceeded 7.6 and 11.4%, respectively. This method is applicable for the modeling and description of possible pharmacological interactions on rat cytochromes P450 1A2 and 2C6/11 or can be used for in vitro evaluation of both cytochromes 1A2 and 2C.

Dynamics and persistence of CYP2D6 inhibition by paroxetine

Paroxetine is both a substrate and an inhibitor of CYP2D6. The objective of the presented study was to determine the persistence of CYP2D6 inhibition after short term (6 weeks) and long term (18·7 ± 10·6 weeks) paroxetine treatment.

Pharmacokinetics of Ciclopirox Olamine after Buccal Administration in Rabbits

BACKGROUND Prevalence of oral mucosal fungal infections increases with the frequent administration of antibiotics, corticosteroids and immunosuppressive drugs. Therapeutically used antifungals are usually associated with a variety of drug interactions. Furthermore, there has been a noticeable increase in microorganisms resistant to these preparations. Mucoadhesive buccal films represent a modern therapeutic system for the treatment of oral mucosal fungal infection paired with a high degree of patient compliance. Ciclopirox olamine applied directly onto the oral mucosa offers an attractive alternative to treatment with systemic antifungals thanks to its low incidence of resistance and side effects. OBJECTIVE The aim of this work was to evaluate the pharmacokinetic parameters of ciclopirox olamine after the buccal application of mucoadhesive film prepared by the solvent casting method. METHOD A chromatographic method using an internal standard was developed and validated for evaluation of ciclopirox olamine plasma concentrations. Method accuracy was 88.5-104.6% and 89.5-99.7% for interday and intraday assays, respectively. RESULTS The pharmacokinetic properties of ciclopirox olamine were studied in New Zealand White rabbits. The mucoadhesive films containing ciclopirox olamine in a total dose of 34.4 (33.0; 35.9) mg kg-1 were applied to all the rabbits. Plasma ciclopirox olamine concentrations were determined during the 12 h following application. The time taken to reach maximum plasma concentration was 1.7 (1.1; 2.2) h after the drug administration with cmax 5.73 (4.18; 7.28) μg mL-1. Overall elimination half-life was 3.8 (1.9; 10.8) h. CONCLUSION The experiment suggests that oral mucoadhesive film may be a valuable alternative ciclopirox olamine administration.

Nonaqueous capillary electrophoresis of dextromethorphan and its metabolites.

This study deals with the nonaqueous capillary electrophoretic separation of dextromethorphan and its metabolites using a methanolic background electrolyte. The optimization of separation conditions was performed in terms of the resolution of dextromethorphan and dextrorphan and the effect of separation temperature, voltage, and the characteristics of the background electrolyte were studied. Complete separation of all analytes was achieved in 40 mM ammonium acetate dissolved in methanol. Hydrodynamic injection was performed at 3 kPa for 4 s. The separation voltage was 20 kV accompanied by a low electric current. The ultraviolet detection was performed at 214 nm, the temperature of the capillary was 25°C. These conditions enabled the separation of four analytes plus the internal standard within 9 min. Further, the developed method was validated in terms of linearity, sensitivity, and repeatability. Rat liver perfusate samples were subjected to the nonaqueous capillary electrophoretic method to illustrate its applicability.

The effect of methamphetamine on biotransformation of ethanol:pilot study

Abstract Methamphetamine is one of the most popular recreational drugs in Central Europe and is often combined with ethanol. Various interactions between these two substances have been described including the influence of administered ethanol on biotransformation of methamphetamine. The aim of the present study was to describe the opposite effect - the influence of methamphetamine on biotransformation of ethanol in rats. Methamphetamine was administered for 10 days (10 mg/kg/day) i.p. and ethanol was delivered as an intragastric bolus (2 g/kg) on the10th day of experiment to both methamphetamine administered rats and control animals. The pharmacokinetic experiment on the whole animal was performed and plasma samples were drawn at the 40th, 120th, 210th and 300th minute after ethanol administration. Ethanol plasmatic levels reached significantly lower values in the 40th and 120th interval when compared to controls. Differences were insignificant in the last two intervals. Our results suggest that chronic methamphetamine administration induces ethanol biotransformation. We suppose that this effect is caused by induction of alcohol dehydrogenase metabolic activity or by allosteric interaction of methamphetamine and this enzyme. More studies have to be conducted to confirm or disprove our hypothesis. Metamfetamin je jednou z nejčastěji zneužívaných drog v regionu Střední Evropy a velmi často je jeho užívání kombinováno s požíváním alkoholu. V minulosti byly popsány rozličné interakce mezi těmito dvěma látkami včetně vlivu ethanolu na biotransformaci metamfetaminu. Cíl této práce je přesně opačný, tedy popsat vliv metamfetaminu na biotransformaci etanolu u potkana. Metamfetamin (10 mg/kg/den) byl zvířatům aplikován ve formě i.p. injekcí 10 dní. Ethanol (2 g/kg intragastricky) byl podán kontrolním i metamfetaminem premedikovaným zvířatům společně s poslední dávkou metamfetaminu. Následně byl proveden farmakokinetický experiment na celém zvířeti s odběrem vzorků krve v následujících časových intervalech od aplikace ethanolu: 40, 120, 210 a 300 minut. Hladiny ethanolu v plazmě stanovené metodou plynové chromatografie byly signifikantně nižší u metamfetaminem premedikovaných zvířat než u kontrol ve 40. a 120. minutě experimentu, zatímco v následujících dvou časových intervalech byl rozdíl nesignifikantní. Naše výsledky naznačují, že chronicky aplikovaný metamfetamin zrychluje biotransformaci ethanolu. Domníváme se, že tento efekt je zprostředkován prostřednictvím alkoholdehydrogenázy buď zvýšení genové exprese nebo alosterickou modulací tohoto enzymu vlivem metamfetaminu. K ověření nebo vyvrácení naší hypotézy je nutné provést další studie.

Determination of Caffeine and its Metabolites in Saliva and Urine as a Measure of CYP1A2 Metabolic Activity

Byla vyvinuta nova citliva a robustni RP-HPLC metoda pro stanoveni kofeinu, 1,7 dimethylxanthinu, 1,7-dimethylmocove kyseliny, 5-acetylamino-6-formylamino-3-methyluracilu, 5-acetylamino-6-amino-3-methyluracilu, 1-methylxanthinu a 1-methylumocove kyseliny ve slinach a moci. Metoda slouži ke stanoveni metabolicke aktivity CYP1A2.

P02-451 - Comparison of risperidone response rate between different CYP2D6 metabolisers

Introduction Risperidone is an antipsychotic used as the first-line treatment of schizophrenia. Risperidone is metabolised by enzyme CYP2D6. Activity of this enzyme can be predicted by genotypization. Objectives To explore the possibility of different response rate to risperidone in first-episode schizophrenia patients with different CYP2D6 genotype. Aim To asses the utility of CYP2D6 pharmacogenetic testing in patients with schizophrenia treated with risperidone. Methods CYP2D6 genotype was assessed in 22 first-episode schizophrenic patients by use of automatic sequencing of DNA isolated from peripheral leukocytes. PANSS score was assessed every week of treatment until the change in medication or patient release. Response was defined as at least 30% reduction in total PANSS. Differences in response rate between groups were tested by Fishers exact test. Results 10 CYP2D6 extensive metabolisers (EM), 8 intermediate metabolisers (IM) and 4 poor metabolisers (PM) were identified. Criteria for response met 4 EM, 4 IM and 1 PM. Differences in response rate between groups were not statistically significant. Conclusions Although group of IM had higher response rate than EM and PM, differences in response rate did not reach statistical significance. Further differences may be found by extending the sample size. An useful approach would be also to examine differences in occurrence of adverse effects and subjective tolerance of the treatment. Acknowledgement The study was supported by the grant of Czech Ministry of Health No. NS 9676-4/2008.