Studies on pharmacokinetics of STS 557 in animal species and man

Biotransformation of Current-Use Progestin Dienogest and Drospirenone in Laboratory-Scale Activated Sludge Systems Forms High-Yield Products with Altered Endocrine Activity

Dienogest (DIE) and drospirenone (DRO) are two fourth-generation synthetic progestins widely used as oral contraceptives. Despite their increasing detection in wastewaters and surface waters, their fate during biological wastewater treatment is unclear. Here, we investigated DIE and DRO biotransformation with representative activated sludge batch incubations and identified relevant transformation products (TPs) using high-resolution mass spectrometry. DIE exhibited slow biotransformation (16-30 h half-life) and proceeded through a quantitative aromatic dehydrogenation to form TP 309 (molar yields of ∼55%), an aromatic TP ∼30% estrogenic as 17β-estradiol. DRO experienced more rapid biotransformation (<0.5 h half-life), and 1,2-dehydrogenation formed the major TP 364 (molar yields of ∼40%), an antimineralocorticoid drug candidate named as spirorenone. Lactone ring hydrolysis was another important biotransformation pathway for DRO (molar yields of ∼20%) and generated pharmacologically inactive TP 384. Other minor pathways for DIE and DRO included hydroxylation, methoxylation, and 3-keto and C4(5) double-bond hydrogenation; distinct bioactivities are plausible for such TPs, including antigestagenic activity, antigonadotropic activity, and pregnancy inhibition effects. Thus, biotransformation products of DIE and DRO during wastewater treatment should be considered in environmental assessments of synthetic progestins, especially certain TPs such as the estrogenic TP 309 of DIE and the antimineralocorticoid spirorenone (TP 364) of DRO.

Prediction of human pharmacokinetics from animal data and molecular structural parameters using multivariate regression analysis: oral clearance

The aim of the study reported here was to develop a regression equation for predicting oral clearance of various kinds of drugs in humans using experimental data from rats and dogs and molecular structural parameters. The data concerning the oral clearance of 87 drugs from rats, dogs, and humans were obtained from literature. The compounds have various structures, pharmacological activities, and pharmacokinetic characteristics. In addition, the molecular weight, calculated partition coefficient (c log P), and the number of hydrogen bond acceptors were used as possible descriptors related to oral clearance in human. Multivariate regression analyses, multiple linear regression analysis, and the partial least squares (PLS) method were used to predict oral clearance in human, and the predictive performances of these techniques were compared by allometric approaches, which have been used in interspecies scaling. Interaction terms were also introduced into the regression analysis to evaluate the nonlinear relationship. For the data set used in this study, the PLS model with the tertiary term descriptors gave the best predictive performance, and the value of the squared cross-validated correlation coefficient (q(2)) was 0.694. This PLS model, using animal oral clearance data for only two species and easily calculated molecular structural parameters, can generally predict oral clearance in human better than the allometric approaches. In addition, the molecular structural parameters and the interaction term descriptors were useful for predicting oral clearance in human by PLS. Another advantage of this PLS model is that it can be applied to drugs with various characteristics.

Progestogens with antiandrogenic properties

Chlormadinone acetate, cyproterone acetate and dienogest are potent, orally active progestogens, which have antiandrogenic instead of partial androgenic activity. They act mainly by blocking androgen receptors in target organs, but also reduce the activity of skin 5alpha-reductase, the enzyme responsible for converting testosterone to the more potent androgen, 5alpha-dihydrotestosterone, in sebaceous glands and hair follicles. Chlormadinone acetate and cyproterone acetate also suppress gonadotropin secretion, thereby reducing ovarian and adrenal androgen production. Combined oral contraceptives (COCs) containing antiandrogenic progestogens provide highly effective contraception (gross and adjusted Pearl indices: 0-0.7 and 0-0.3, respectively) with excellent cycle control. Furthermore, COCs containing 2mg of chlormadinone acetate or cyproterone acetate plus 30 or 35 microg of ethinylestradiol produced improvement or resolution of seborrhoea in 80% of users, acne in 59-70%, hirsutism in 36% and androgen-related alopecia in up to 86%. These COCs are generally well tolerated, the main adverse effects being nonspecific or as expected for a COC (headache, breast tenderness and nausea). They have no clinically relevant effects on metabolic or liver functions or on bodyweight. Effects on mood and libido are uncommon (<3.5% and <6% of women, respectively). COCs containing antiandrogenic progestogens are likely to be particularly valuable in women with pre-existing androgen-related disorders who require contraception. They also increase the choice of products available for women with normal skin and hair who are concerned about the possibility of developing seborrhoea or acne with other COCs.

Intestinal absorption of ST-1435 in rats

The intestinal absorption of a 19-norprogesterone (ST-1435) was studied in rats after an oral dose of 5 mg ST-1435/kg body weight. Blood samples were collected simultaneously from the portal vein and by cardiac puncture. Plasma ST-1435 concentrations were measured from the samples by radioimmunoassay (RIA). Chromatographic purification of ST-1435 in rat plasma revealed a metabolite cross-reacting in the RIA. A peak concentration of 240 ng ST-1435/ml was found in portal plasma 75 minutes after administration, indicating that the steroid is well absorbed from the small intestine. However, in spite of the relatively high dose used, the plasma concentrations of ST-1435 in the systemic circulation remained low and of short duration. Thus, it seems that ST-1435 in hepatic portal blood is extensively taken-up and metabolized by the liver, resulting in low plasma concentrations of ST-1435 in the systemic circulation when the steroid is administered orally. This is also supported by the observation that higher metabolite levels were found in systemic plasma than in portal plasma during the first 90 minutes after administration. This pronounced first-pass effect may also explain why in women oral administration of ST-1435 has failed to result in any biological effect.