Gender difference in antidiuretic response to desmopressin.

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.

Dose-exposure proportionality of a novel recombinant follicle-stimulating hormone (rFSH), FE 999049, derived from a human cell line, with comparison between Caucasian and Japanese women after subcutaneous administration.

BACKGROUND AND OBJECTIVES: FE 999049 is a novel recombinant follicle-stimulating hormone (rFSH) preparation expressed by a human cell line (PER.C6(®)), in contrast to existing rFSH preparations expressed by Chinese hamster ovary (CHO) cell lines. Since the individual dose of rFSH may be altered depending on the response in women undergoing assisted reproductive technologies, knowledge on the dose-exposure linearity and proportionality is important. The purpose of these studies was to investigate the dose-exposure linearity and proportionality properties of FE 999049 with a comparison between Caucasian and Japanese women. This is the first study in Japanese women regarding pharmacokinetics of rFSH. METHODS: Forty-eight Caucasian and 31 Japanese healthy women of reproductive age were pituitary down-regulated to suppress endogenous FSH. Following single subcutaneous administration of 37.5, 75, 150, 225, or 450 IU (Steelman-Pohley assay), the serum FSH concentration was followed over 10 days. RESULTS: The dose-dependent pharmacokinetic parameters of FE 999049, area under the serum concentration-time curve (AUC) and maximum serum concentration (C max), showed dose-exposure linearity and proportionality over 150-450 IU in Caucasian women, the dose interval available for analysis, and 75-450 IU in Japanese women, which was the dose interval investigated. Comparison between Caucasian and Japanese women showed no differences between the populations. The dose-independent parameters were similar over all doses in both populations. FE 999049 was safe and well tolerated at all doses in both populations with few, mostly mild, adverse events. CONCLUSION: The results demonstrate dose-exposure proportionality and a predictable dose-dependent exposure of FE 999049, with no differences in Caucasian and Japanese women of reproductive age.

Different pharmacokinetic and pharmacodynamic properties of recombinant follicle-stimulating hormone (rFSH) derived from a human cell line compared with rFSH from a non-human cell line.

Pharmacokinetic and pharmacodynamic properties of a novel recombinant follicle-stimulating hormone (rFSH) preparation (FE 999049), expressed by a human cell line (PER.C6), was compared with an rFSH preparation (follitropin α) expressed by a Chinese hamster ovary (CHO) cell line in healthy pituitary-suppressed women. Following single intravenous administration of 225 IU (Steelman-Pohley assay), the clearance was lower, 0.31 versus 0.44 L/h, for FE 999049 than for follitropin α. Likewise, the apparent clearance after repeated daily subcutaneous administrations was lower, 0.58 versus 0.99 L/h, and AUC and C(max) higher, 1.7- and 1.6-fold. The absolute bioavailability after a single subcutaneous dose of 450 IU was similar for both preparations, 60-65%. After repeated subcutaneous administration the elimination half-life was approximately 30 and 24 hours for FE 999049 and follitropin α. The ovarian responses by number of follicles and serum concentrations of inhibin B and estradiol, were higher with FE 999049 than with follitropin α, AUC and C(max) for the two latter being >1.6-fold greater with FE 999049 than with follitropin α. These results indicate that administration of equal doses of FE 999049, expressed in a human cell line, and follitropin α, expressed in a CHO cell line, display different pharmacokinetic and pharmacodynamic properties in humans.

Pharmacokinetics and bioavailability of a new testosterone gel formulation in comparison to Testogel® in healthy men.

This randomized, open-label, multiple-dose three-way cross-over study compared the pharmacokinetics of a new testosterone gel formulation in two strengths, testosterone gel 1% and testosterone gel 2% (FE 999303), with Testogel® in 11 testosterone-suppressed healthy men. Subjects received one of six treatment sequences; 50 mg of testosterone was administered once daily for 7 consecutive days, with different treatments separated by washout-periods of 6-9 days. Testosterone gel 1% and testosterone gel 2% displayed greater relative bioavailability (2.6- and 1.6-fold, respectively) than Testogel on Day 1, which persisted, to a smaller extent, on Day 7. Initial absorption was highest and most rapid for testosterone gel 1% and 2%, showing apparent first-order absorption kinetics. Maximum serum concentrations (Cmax ) were 6.25 and 2.97 ng/mL, respectively, occurring ∼5-6 hours post-application on Day 1 versus Cmax of 1.71 ng/mL after ∼24 hours with Testogel, showing apparent zero-order absorption kinetics. Similar differences were observed on Day 7. All treatments appeared to reach approximately the same steady-state level within the first 24 hours. No application-site skin reactions occurred with any preparation. In conclusion, the new testosterone formulation showed higher bioavailability, and the ability to deliver more testosterone in a smaller volume.

A mechanism-based integrated pharmacokinetic enzyme model describing the time course and magnitude of phenobarbital-mediated enzyme induction in the rat.

PURPOSE: To characterize the magnitude, time course, and specificity of phenobarbital (PB)-mediated enzyme induction, and further, to develop an integrated pharmacokinetic (PK)-enzyme model describing the changes in the activities of CYP enzymes as well as in the PK of PB. METHODS: PB plasma concentrations and in vitro activities of several CYP enzymes were measured in rats treated with PB between 0 and 14 days. A PB PK-enzyme induction model was developed using the program NONMEM: . RESULTS: PB treatment both induces and reduces the activity of CYP enzymes by stimulating the enzymes' formation or elimination rates. Certain CYP enzymes affected the PB PK through autoinduction. The half-life of the induction process was estimated to be 2 days for CYP1A2, CYP3A1/2, and CYP2B1/2, and 3 days for androstenedione producing enzymes. The CYP2C11 activity was rapidly reduced by PB treatment. A lag time for the PB autoinduction was observed. This lag time is explained by the rate difference between induction and reduction in CYP activities. CONCLUSION: To our knowledge, this is the first example of an induction model that simultaneously describes plasma PK and in vitro data. It does so by integrating the bidirectional interaction between drug and enzymes in a mechanistic manner.

Quantitative analysis of eight testosterone metabolites using column switching and liquid chromatography/tandem mass spectrometry.

The rate at which testosterone is metabolized to different singly hydroxylated metabolites has been widely used as an in vitro marker for activity of different CYP450 enzymes. The interest in extra-hepatic metabolism, e.g. due to metabolism in the gut wall, has increased during the last decade. Measurement of extra-hepatic enzyme activity using testosterone as a substrate requires a highly sensitive analytical method. A new liquid chromatography/electrospray tandem mass spectrometry (LC/MS/MS) method, using column switching for online cleaning and desalting of samples, was developed and validated for analysis of 2alpha-, 2beta-, 6alpha-, 6beta-, 7alpha-, 16alpha-, and 16beta-hydroxytestosterone and androstenedione. The samples were injected on a SB-CN column and detection was performed using MS/MS. The limits of quantification ranged from 0.3 to 3.33 nM for the different metabolites. The validated method was used to quantify the enzyme activity in rat intestine mucosa. The formation rates of 16alpha-, 16beta-hydroxytestosterone and androstenedione were quantified, and 2beta-and 6beta-hydroxytestosterone were formed above the limits of detection.