Jaroslav Kvetina

Pharmacokinetics of tramadol is affected by MDR1 polymorphism C3435T

Dear Professor Dahlqvist, We have read with interest the articles by Pedersen et al. and Wang et al. who highlighted the importance of functional polymorphisms of CYP2D6 on the pharmacokinetics of tramadol and its major metabolite O-demethyltramadol in recent issues of the European Journal of Clinical Pharmacology [1, 2]. The pharmacology of tramadol is unusually complex, having at least 11 unconjugated metabolites and 12 conjugated compounds [3]. There are three major metabolic pathways, CYP2D6, CYP3A, and CYP2B6, forming Oand N-demethylated metabolites. Tramadol is believed to undergo first-pass metabolism, reducing its bioavailability to approximately 80% after oral administration. The CYP2D6-dependent pharmacokinetics of tramadol is usually also reflected in increased bioavailability in poor metabolizers (PM) compared with extensive metabolizers (EM). Surprisingly, Pedersen et al. did not observe any significant difference between bioavailability of tramadol in EMs and PMs, while large interindividual variability was noted [1]. It is recognized that the bioavailabity of some drugs can be substantially affected by active transporters expressed in the gut lumen, like P-glycoprotein. We recently conducted a study in order to uncover MDR1 genotype-dependent variations in pharmacokinetic parameters of tramadol and O-demethyltramadol. Twenty-one healthy young volunteers selected from our database participated in the study after providing informed consent. Presence of CYP2D6*3, *4, *5, *6 alleles and gene duplications was analyzed using PCRand RFLPbased methods. MDR1 polymorphisms C3435T and G2677T/A were also detected. Three groups of seven CYP2D6 EM, heterozygous EM, and PM subjects were investigated. Four and nine subjects were homozygous carriers of C3435 and T3435 alleles, respectively. Each volunteer was administered a 100-mg sustainedrelease tramadol tablet (Tramal Retard 100 mg, Zentiva Praha a.s.), and plasma concentrations of (R,S)-(±)-tramadol (TMD) and (±)-O-demethyltramadol (M1) were analyzed by HPLC at baseline and at 2.5, 4, 8, 12, and 24 h post-dose. The average Cmax and AUC0–24 values of TMD increased slightly in groups with increasing numbers of 3435T alleles of MDR1 irrespective of CYP2D6 status. The mean (SD) Cmax values of TMD were 495.4 (91.1), 529.3 (161.7), and 600.2 (179.9) nmol/l in 3435CC, 3435CT, and 3435TT groups, respectively. Corresponding values for AUC0–24 in the respective groups were 7,393.9 (2,299.1), 7,710.1 (3,304.7), and 8,478.8 (3,771.0) nmol·h/l. The differences, however, did not reach the level of statistical significance. Interestingly, a similar trend was not observed for M1, for which production was more dependent on relative numbers of CYP2D6 extensive metabolizers. Detailed analysis focused on comparison of subjects according to mixed CYP2D6 and MDR1 genotypes. Figure 1 shows pharmacokinetics profiles of TMD and Eur J Clin Pharmacol (2007) 63:419–421 DOI 10.1007/s00228-006-0255-3

Use of a propafenone metabolic ratio as a measure of CYP2D6 activity.

AIM The antiarrythmic drug propafenone is metabolized to its main metabolite by CYP2D6, suggesting that its metabolic ratio may be used for CYP2D6 phenotyping. However, reported ratios obtained from plasma concentrations did not reflect the phenotype. The objective of this paper was to find optimal conditions for plasma sampling based on pharmacokinetic data and to investigate whether propafenone/metabolite ratios reflect the CYP2D6 phenotype. PATIENTS, MATERIALS AND METHODS The present study was conducted in 14 healthy volunteers phenotyped for CYP2D6 activity by a sparteine test. A single dose of oral propafenone (Profenorm PRO.MED.CS Praha a.s.) was administered, and venous blood samples were taken up to 24 hours thereafter. Propafenone and hydroxypropafenone were measured by HPLC. RESULTS The individual data for the respective propafenone/metabolite metabolic ratio in plasma samples taken at tmax correlated well with the sparteine metabolic ratio used routinely for CYP2D6 phenotyping. However, when the samples were taken 4 hours after drug intake, the correlation was poor. CONCLUSION The results indicate a possibility to use the propafenone metabolic ratio for determination of the CYP2D6 phenotype in plasma samples taken at single time point (close to the Cmax, i.e. 2 hours after drug intake).

Morphometric analysis of the porcine gastrointestinal tract in a 10-day high-dose indomethacin administration with or without probiotic bacteria Escherichia coli Nissle 1917

Background: Nonsteroidal anti-inflammatory drugs may cause severe injury to all parts of the gastrointestinal tract. It has been hypothesised that probiotic bacteria might reduce this adverse effect. The aim of this study was to perform a morphometric evaluation of the gastrointestinal tract in experimental pigs treated using a 10-day high-dose of indomethacin with or without Escherichia coli Nissle 1917 (EcN). Methods: Twenty-four healthy mature pigs were included: Group A (controls; 6 animals), Group B (EcN; n = 6), Group C (indomethacin; n = 6) and Group D (EcN & indomethacin; n = 6). EcN (3.5 × 1010 live bacteria/day for 14 days) and/or indomethacin (15 mg/kg/day for 10 days) were administered. Specimens of the stomach, small and large bowel were routinely processed for microscopic examination. The height of glandular mucosa, height and width of interfoveolar spaces and villi and basement size of epithelial cells were evaluated. Results: Different effects of indomethacin and EcN on particular parts of the gastrointestinal tract were shown. The indomethacin and probiotics group demonstrated a significantly lower height of cryptal mucosa and colonocytes and widening of the basement size of colonocytes compared to controls (p = 0.004; p < 0.001; p = 0.025). The height of cryptal mucosa was significantly higher in the EcN group compared to controls (p = 0.001). Conclusions: Indomethacin alone induced marked adaptation of the gastric mucosa. EcN alone provided a significant favourable trophic effect on the colonic mucosa. However, indomethacin and probiotics administered together comprise the worst impact on all porcine stomach, small and large bowel.

The Importance of Wireless Capsule Endoscopy for Research into the Intestinal Absorption Window of 5-Aminosalicylic Acid in Experimental Pigs

BACKGROUND Absorption windows in particular segments of the small intestine can contribute to the development of orally administered drug formulations and can limit the bioavailability of released compounds. OBJECTIVE The aim of this study was to evaluate use of wireless capsule enteroscopy regarding the disintegration kinetic process of tablets in the small intestine and its comparison with the levels of the model drug (5- aminosalicylic acid; 5-ASA), and its majority metabolite (N-acetyl-5-aminosalicylic acid; N-acetyl-5-ASA) in blood plasma. METHODS Tablets were endoscopically introduced into the duodenum and their disintegration was monitored using wireless capsule enteroscopy in anaesthetised pigs. In parallel, blood plasma time profiles of the model drug (5-ASA) released from tablets and its metabolite (N-acetyl-5-ASA) were detected. RESULTS The disintegration of tablets was evident in the proximal jejunum (until the 90-minute mark) and culminated at the 3rd hour. The maximum plasmatic concentration of 5-ASA was reached at the 3rd hour and in the case of its metabolite (N-acetyl-5-ASA) at the 4th hour. CONCLUSION The study demonstrated the advantage of combination of wireless capsule enteroscopy and bioanalytical determination of pharmacokinetic parameters in an animal experiment to localise the disintegration site of solid dosage form and following kinetics of intestinal absorption of the released active agent.

Probiotics: Preclinical Testing for Verification of Their Gastrointestinal Effectiveness

Abstract Currently, no studies exist addressing the issue of influence of probiotics on pharmacokinetics of concurrent conventional drug administration. In the present chapter we document some findings from our own preclinical experimental studies. We describe methodology and results from studies evaluating the influence of probiotics (especially of Escherichia coli Nissle 1917) on absorption and biotransformation processes of model drugs and describe the prophylactic effects reducing gastrointestinal injury (experimentally induced with indomethacin and dextran sodium sulfate).

Sa1349 Impact of Water Load Test on the Gastric Myoelectric Activity in Experimental Pigs

Objectives Epidemiology of uninvestigated dyspepsia was studied in the Czech Republic for the first time in 2001 (1). The aim this current multi-centre prospective study was to evaluate dyspepsia using the samemethods in a representative sample of general unselected population from the same geographical areas 10 years later. Methods A total of 22 centres entered the study. They were spread over the whole country, corresponding well to the geographical distribution of the Czech population. A total of 1,836 subjects (863 males and 973 females; aged 5-98 years) took part in the study and responded to the question on prevalence of dyspepsia. Complete data on variables used in our analysis was available for 1,685 subjects. The proportion of subjects reporting dyspepsia did not differ significantly between the restricted sample and the group excluded from multivariable analyses. Helicobacter pylori (Hp) status was investigated in all subject by means of 13C-urea breath test. Results In subjects aged 5-24 years, when we analyzed determinants of dyspepsia by type (subgroup A: dyspepsia as the only long-lasting symptom vs. subgroup B: dyspepsia as a part of the complex of other complaints or previously recognized diseases), we noted somewhat stronger increase in risk of dyspepsia A with age (OR 1.15 per 1 year of age, 95% CI 1.05-1.26, adjusted for gender) and with current use of antibiotics (OR 3.23 in users vs. non-users, 95% CI 0.87-11.9). In subjects aged 25+ years, when analyzed by type of dyspepsia, a statistically significant negative association of age with dyspepsia of type A became apparent (OR 0.95 per 1 year of age, 95% CI 0.94-0.97) while the association between age and dyspepsia type B was also statistically significant albeit positive (OR 1.02 per 1 year of age, 95% CI 1.01, 1.04). Furthermore, subjects who were single were at lower risk of dyspepsia type B (OR 0.46 in single vs. married, 95% CI 0.21-0.99, adjusted for age and gender). The unexpected protective effect of elementary education appeared also to be stronger for dyspepsia type B (OR for elementary vs. university educated 0.25, 95% CI 0.07-0.86, adjusted for age and gender). Hp negative subjects reported dyspepsia in 4.1% (aged 5-24 years) and 18.1 % (aged 25+ years). In Hp positive subjects, dyspepsia was present in 7.1% (aged 5-24 years; OR 1.45, 95% CI 0.41, 5.16) and 16.3% (aged 25+ years; OR 0.85, 95% CI 0.60, 1.21, adjusted for gender and age). Conclusions Despite the substantial decrease of Hp infection in the Czech Republic over the past 10 years, the prevalence and basic socio-demographic determinants of uninvestigated dyspepsia did not change significantly. Reference: Rejchrt et al. Eur J Gastroenterol Hepatol 2008; 20: 898-905. This study was supported by the research grant MH CZ NT115245/ 2010 and by the programme PRVOUK 3708.