Phase I and II metabolism and MRP2-mediated export of bosentan in a MDCKII-OATP1B1-CYP3A4-UGT1A1-MRP2 quadruple-transfected cell line.

BACKGROUND AND PURPOSE: Hepatic uptake (e.g. by OATP1B1), phase I and II metabolism (e.g. by CYP3A4, UGT1A1) and subsequent biliary excretion (e.g. by MRP2) are key determinants for the pharmacokinetics of numerous drugs. However, stably transfected cell models for the simultaneous investigation of transport and phase I and II metabolism of drugs are lacking. EXPERIMENTAL APPROACH: A newly established quadruple-transfected MDCKII-OATP1B1-CYP3A4-UGT1A1-MRP2 cell line was used to investigate metabolism and transcellular transport of the endothelin receptor antagonist bosentan. KEY RESULTS: Intracellular accumulation of bosentan equivalents (i.e. parent compound and metabolites) was significantly lower in all cell lines expressing MRP2 compared to cell lines lacking this transporter (P < 0.001). Accordingly, considerably higher amounts of bosentan equivalents were detectable in the apical compartments of cell lines with MRP2 expression (P < 0.001). HPLC and LC-MS measurements revealed that mainly unchanged bosentan accumulated in intracellular and apical compartments. Furthermore, the phase I metabolites Ro 48-5033 and Ro 47-8634 were detected intracellularly in cell lines expressing CYP3A4. Additionally, a direct glucuronide of bosentan could be identified intracellularly in cell lines expressing UGT1A1 and in the apical compartments of cell lines expressing UGT1A1 and MRP2. CONCLUSIONS AND IMPLICATIONS: These in vitro data indicate that bosentan is a substrate of UGT1A1. Moreover, the efflux transporter MRP2 mediates export of bosentan and most likely also of bosentan glucuronide in the cell system. Taken together, cell lines simultaneously expressing transport proteins and metabolizing enzymes represent additional useful tools for the investigation of the interplay of transport and metabolism of drugs.

[Porphyrin catalysts: a tool for preparation of metabolite models]. / Les catalyseurs porphyriniques: un outil pour la préparation de modèles de métabolites.

The porphyrin complexes of manganese catalysts are biomimetic catalysts whose structural analogy with the active site of cytochrome P-450 enzymes can be used to obtain synthetic models of therapeutic agent metabolites. Mn(TDCOO)Cl, a second generation porphyrin, has proven robust enout to be used for scaled-up production in the presence of hydrogen peroxide and imidazole. For this purpose, an improvement in substrate oxidation was obtained by adjunction of formic acid to the reaction medium which preserved the cocatalyst and the catalyst. It was shown that addition of acid played an active role in the oxidation process. After this optimization, the system was used to oxidate the two enantiomers of methyloctalone, an essential chiral intermediate in the synthesis of terpenoids and steroids. The efficacy of this biomimetic method for the preparation of large amounts of oxidized chiral synthons was better than obtained with biological ex vivo pathways.

Pharmacokinetics of reboxetine in healthy, elderly volunteers.

The pharmacokinetic characteristics of reboxetine, a unique selective noradrenaline reuptake inhibitor (selective NRI) for the treatment of depression, were studied in 12 healthy, elderly volunteers (mean age 81 years +/- 9 years). All subjects received a single 4-mg dose of reboxetine, and plasma reboxetine concentrations were measured by HPLC. Reboxetine was well tolerated by all subjects. Exposure to reboxetine was higher in this group of very elderly subjects, compared with data obtained in a similar study of young, healthy volunteers. Cmax in the elderly was 271 +/- 86 ng/ml, compared with 111 +/- 28 ng/ml in the young subjects after a single 4-mg dose, although in both groups Cmax was observed after 2 h. The AUC infinity was nearly four times that in the younger subjects (8345 +/- 3107 ng.h/ml vs. 2106 +/- 881 ng.h/ml) and the t1/2 was twice as long (24 +/- 6 h vs. 12 +/- 3 h). Renal clearance was also reduced. Reboxetine 8-10 mg/day has been effective and well tolerated in clinical trials in non-elderly depressed patients. The increased exposure to reboxetine observed in our very elderly subjects supports a reduction of the starting dose to 4 mg/day (in two divided doses) in the elderly.

Blind loop syndrome: an unusual cause of panniculitis.

We describe a 52-year-old woman with panniculitis and blind loop syndrome. She had undergone a gastrectomy for peptic ulcer 4 years before. Tender erythematous nodules on her palms and soles were associated with diarrhea and weight loss. A biopsy specimen revealed septal and lobular panniculitis. A glucose hydrogen breath test was consistent with bacterial overgrowth. These results were consistent with panniculitis associated with a blind loop syndrome. Only four cases of this association have been reported previously.

[Therapeutic principles in gastroesophageal reflux]. / Principes thérapeutiques du reflux gastroesophagien.

Gastroesophageal reflux is a common disease. Its chronic course, even if mild, is sometimes complicated by erosive oesophagitis. Drug therapy acts against gastric acidity and motility disorders. Treatment of gastroesophageal reflux disease has three aims: improvement of symptoms and quality of life, healing erosive lesions and prevention of symptomatic and endoscopic relapses. Non-drug measures are always useful, even if their efficacy is not well established. Initial therapy of a symptomatic reflux or mild oesophagitis is most of the time effective (antacids, prokinetics, H2 receptor antagonists). Proton-pump inhibitors are also effective in healing and preventing severe oesophagitis. Questions about long-term treatment adverse events with powerful acid inhibitors, such as hypergastrinemia and the risk of gastric carcinoid tumours seem to be resolved. Studies are requested to define the optimal long-term maintenance treatment with cisapride, H2 receptor antagonists or proton-pump inhibitors at low doses in prevention of symptomatic and mild oesophagitis relapses.

[Critical examination of scoring systems in therapeutic trials]. / Examen critique des grilles de lecture des essais thérapeutiques.

Scoring systems give a check-list and methodological informations which have to be found in controlled therapeutic trials reports and papers. These systems try to quantify each item to give a global score. The Chalmer's list is the most wellknown. It allows a balance in scoring taking in account the quality of the endpoints. Other lists are more simple. Many check-lists allow the scoring of the methodological design or the statistical analysis. In all systems the major methodological points are: the randomization, the description of the population, the double blind, the estimation of the sample size, the handling of withdrawal and drop out, the major endpoint, the patients follow-up, the statistical analysis and the data presentation. All these scoring systems have several limits: the quantitative evaluation of each item is subjective and the point scoring has never been validated, some scoring systems are old and don't integrate new methodological methods, the scores never included the clinical interest of the trial, some items are questionable, others are forgotten (intention to treat analysis, steering comity...). Scoring systems allow a control of the methodological quality of clinical trials but don't include the clinical or scientific interest of the study. These systems are a useful methodological tool for publication process in medical journals and for new drugs authorization. The evaluation by authors themselves of the quality of their papers using a standardized scoring system could clarify the reviewers decisions.

A randomised clinical trial of the effect of informed consent on the analgesic activity of placebo and naproxen in cancer pain.

To determine whether informed consent in a therapeutic trial modifies the analgesic effect of naproxen and placebo, we conducted a prospective, randomised, single dose, placebo-controlled trial. Patients were randomly selected to receive or not information concerning the study. All patients included were then given a single dose of naproxen and placebo according to a crossover, double-blind design. Forty-nine patients with mild or moderate cancer pain which did not need narcotic analgesics entered the study. Twenty-five received both treatments without any information and constituted the uninformed group. Twenty-four had a complete information about the trial; six refused to participate. The 18 others constituted the informed-consent group. Visual analogue scales of pain before and 30, 60, 120 and 180 min after the intake of naproxen and placebo were recorded. As an analgesic, naproxen was more effective than placebo in both groups of patients (p = 0.001). For naproxen as well as for placebo, the analgesic effect was better in the informed-consent group compared to the uninformed group (p = 0.012). The difference in therapeutic activity between naproxen and placebo was moderately higher in the uninformed patients (p = 0.08). We concluded that, in contrast with parallel studies, giving information in a crossover, placebo-controlled trial may increase the apparent efficacy of both the tested agent and the placebo, and decrease the perceived difference the two.

What is the better formulation of microencapsulated potassium chloride?

A single blind cross-over study was performed comparing a new microencapsulated potassium chloride tablet (MET) with two reference formulations of oral potassium, namely potassium chloride solution (PS), and microencapsulated potassium chloride capsules (MEC), in 18 normal healthy volunteers. The potassium chloride induced change in gastric potential difference (PD) of the mucosa was the main criterion of comparison and was assessed by the area above curve (AAC), the total duration of the effect (TDE), the maximal variation of PD (delta MAX), and the aggression index (AI). The results showed that all three formulations induced a fall in PD; the delta MAX and AAC were significantly greater for PS indicating a higher aggressive effect of the solution; MET had significantly less aggressive effect than MEC when assessed by all parameters.

Protection against aspirin-induced gastric lesions by lansoprazole: simultaneous evaluation of functional and morphologic responses.

The protective effect of lansoprazole, a new proton pump inhibitor, against aspirin-induced gastric lesions was studied in a double-blind crossover trial with a simultaneous measure of the functional capacities of the mucosal barrier (by a recording of the gastric potential difference) and of the morphologic changes in the mucosa (by gastric endoscopy). After 1 week of treatment with lansoprazole (30 mg per day) or placebo, each healthy volunteer received 1 gm aspirin by mouth. Recording of the gastric potential difference lasted for 3 hours and was followed by gastric endoscopy. Morphologic lesions induced by aspirin were effectively prevented by lansoprazole: Lanza score was 0.67 +/- 0.98 (mean +/- SD) versus 2.25 +/- 1.1 with placebo (p < 0.005, ANOVA). Conversely, the decrease in the gastric potential difference was similar. The inhibition of acid secretion induced by lansoprazole was therefore sufficient to prevent aspirin-induced mucosal lesions without reinforcing the defense capacities of the mucosa. This simple pharmacologic model makes it possible to simultaneously evaluate the functional and morphologic effects of aspirin intake on the gastric mucosa.