Increased age and female gender are well-known risk factors for the development of desmopressin-induced hyponatremia. However, little focus has been on exploring gender differences in the antidiuretic response to desmopressin. Based on an exploratory analysis from three clinical trials, we report a significant gender difference in the effects of desmopressin on nocturnal urine volume that could not be explained by pharmacokinetic differences. Mean desmopressin concentration profiles were tested for covariates, and age and gender were not statistically significant and only weight was significant for log(C(max)) (P = 0.0183) and borderline significant for log(AUC) (P = 0.0571). The decrease in nocturnal urine volume in nocturia patients treated with desmopressin over 28 days was significantly larger for women at the lower desmopressin melt doses of 10 and 25 μg than for men. The ED(50) for men was modeled to be 43.2 μg and 16.1 μg for women, with the ED(50) men/women estimated to be 2.7 (1.3-8.1 95% CI), corresponding to significantly higher sensitivity to desmopressin in women. An increasing incidence of hyponatremia with increasing dose was found, and at the highest dose level of 100 μg decreases in serum sodium were approximately twofold greater in women over 50 yr of age than in men. A new dose recommendation stratified by gender is suggested in the treatment of nocturia: for men, 50- to 100-μg melt is an efficacious and safe dose, while for women a dose of 25 μg melt is recommended as efficacious with no observed incidences of hyponatremia. Areas for further research are proposed to uncover pathophysiological mechanism(s) behind these gender differences.

Aims  The purpose of this human intestinal perfusion study was to investigate the effect of ketoconazole on the jejunal permeability and first‐pass metabolism of (R)‐ and (S)‐verapamil in humans. Methods  A regional single‐pass perfusion of the jejunum was performed using a Loc‐I‐Gut® perfusion tube in six healthy volunteers. Each perfusion lasted for 200 min and was divided into two periods of 100 min each. The inlet concentration of (R/S)‐verapamil was 120 mg l−1 in both periods, and ketoconazole was added at 40 mg l−1 in period 2. (R/S)‐verapamil was also administered as a short intravenous infusion of 5 mg, over a period of 10 min. The appearance ratios of the CYP3A formed metabolites (R)‐ and (S)‐norverapamil were also estimated in the outlet jejunal perfusate. Results  The effective jejunal permeability (Peff) of both (R)‐ and (S)‐verapamil was unaffected by the addition of ketoconazole in period 2 suggesting that ketoconazole had no effect on the P‐glycoprotein mediated efflux. However, the appearance ratio of both (R)‐ and (S)‐norverapamil in the outlet jejunal perfusate decreased in the presence of ketoconazole. The rate of absorption into plasma of (R)‐ and (S)‐verapamil increased despite the low dose of ketoconazole added, indicating an inhibition of the gut wall metabolism of (R/S)‐verapamil by ketoconazole. Conclusions  Ketoconazole did not affect the jejunal Peff of (R/S)‐verapamil, but it did increase the overall transport into the systemic circulation (bioavailability), probably by inhibition of the gut wall metabolism of verapamil. This might be due to ketoconazole being less potent as an inhibitor of P‐glycoprotein than of CYP3A4 in vivo in humans.

The aim of this study was to develop a model describing the carbamazepine autoinduction and the carbamazepine-mediated induction of CYP3A4, CYP1A2, and P-glycoprotein. Seven healthy volunteers were dosed with carbamazepine over 16 consecutive days. The CYP3A4, CYP1A2, and P-glycoprotein activities were assessed, using midazolam, caffeine, and digoxin as probe substrates, on 12 occasions, covering the preinduced state and the onset and termination of the induction process. The data were evaluated using a mechanistic pharmacokinetic approach in NONMEM. The induction processes were described using turnover models, with carbamazepine and carbamazepine-10,11-epoxide as the driving force of the induction. The half-lives of CYP3A4 and CYP1A2 were estimated to be 70 and 105 h, respectively. P-glycoprotein was not affected by the carbamazepine treatment. The possibility of modeling the pharmacodynamics of enzyme induction using a turnover model was illustrated, and the time course of the process was estimated with good precision.

Fluvastatin is extracted by the liver to a large extent (about 70%) and has a short half-life after both oral and intravenous administration. In this study, the human jejunal effective permeability and the fraction absorbed for these four drugs were better predicted by log D (pH 6.5) than both the molecular size and the hydrogen bond number.