Urinary excretion of 6 beta-hydroxycortisol in women during treatment with different oral contraceptive formulations

Use of endogenous cortisol 6β-hydroxylation clearance for phenotyping in vivo CYP3A activity in women after sequential administration of an oral contraceptive (OC) containing ethinylestradiol and levonorgestrel as weak CYP3A inhibitors

The present study was undertaken to evaluate the time courses of in vivo cytochrome P450 3A (CYP3A) inhibition in four healthy women after sequential administration of an oral contraceptive (OC) containing ethinylestradiol and levonorgestrel, using 6β-hydroxylation clearance of endogenous cortisol (CLm(6β)) as a new index for CYP3A phenotyping. The 6β-hydroxylation clearance (CLm(6β)) was followed every 2h from 9:00 or 11:00 to 17:00 on days 0 (baseline), 1, 2, 21, and 28 during a single menstrual cycle. The serum concentrations of endogenous estradiol and progesterone were also measured. The time course data of CLm(6β) clearly demonstrated 43-64% inhibition of CYP3A activity in women taking a low daily dose of the OC for 21days. The average CLm(6β) levels that were suppressed by the OC in four women were extremely low (0.60-1.23mL/min) compared with the normal CLm(6β) range (1.5-3.5mL/min) that was obtained from 49 healthy subjects in our previous study. The in vivo inhibitory potencies (43-64%) obtained in this study were stronger than expected from reported in vitro studies (∼20%). Furthermore, it would take at least seven days to return to the baseline activity of CYP3A after discontinuation of the OC. The results presented here should provide important information on the inhibitory effect of OC on the CYP3A activities in women, which are involved in the metabolism of a number of drugs with a narrow therapeutic range.

Illicit treatments in cattle and urinary 6beta-hydroxycortisol/cortisol ratio

Dexamethasone (DXM) is often illegally used as a growth promoter. To identify indirect biomarkers of illicit treatments, the urinary ratio between 6beta-hydroxycortisol (6beta-OHF) and cortisol (F) was measured in urines obtained from bulls experimentally treated per os and intramuscularly (i.m.) with different DXM dosages. Dexamethasone, given per os at low doses elicited an early and lasting significant reduction of 6beta-OHF/F. No significant variations were seen in urines from bulls given DXM intramuscularly. These results suggest 6beta-OHF/F as a rapid, non-invasive, screening test for oral, low-dose, long-term corticosteroid treatment in cattle. Further studies are required to go deep inside the biochemical and molecular events underlying such an effect.

Microsomal enzyme induction and clinical aggravation of porphyria: the evaluation of human urinary 6beta-hydroxycortisol/cortisol ratio as the index of hepatic CYP3A4 activity

The clinical aspect of porphyria has been investigated, and it is well known that porphyrinogens such as estrogens and alcohol or other inducers of P450 isoenzymes exacerbate the porphyric state. However, there can be a delay in diagnosing porphyria and a difficulty in selecting safe medicine for it even today. A 21-year-old woman developed epilepsy, disturbance of mental state, and spastic tetraparesis during the convalescent period after acute viral encephalitis. She was diagnosed with porphyria after the fifth hospitalization. In the course of modifying her anticonvulsant regimen, the authors examined the 6beta-hydroxycortisol/cortisol ratio (6beta-OHF/F) in her urine, which can be the index of hepatic CYP3A4 activity, with electrospray ionization/mass spectrometry/mass spectrometry (ESI/MS/MS). Generalized and partial complex seizures, other neurological signs and symptoms, and laboratory data were improved after modification of her anticonvulsant regimen. This is the first report of evaluating the urinary 6beta-hydroxycortisol/cortisol ratio in a case of porphyria.

DEET (N,N-diethyl-m-toluamide) alone and in combination with permethrin increased urinary excretion of 6beta-hydroxycortisol in rats, a marker of hepatic CYP3A induction

In this study, the ratio of 6beta-hydroxycortisol (6beta-OHF) to free cortisol (F) was determined in urine following a single dermal dose of 400 mg/kg of DEET (N,N-diethyl-m-toluamide), and 1.3 mg/kg of permethrin, alone and in combination, in rats. Urine samples were collected at 2, 4, 8, 16, 24, 48, and 72 h after application. Recoveries of 6beta-OHF and cortisol (F) from control urine samples were between 75 and 85%, with limits of detection at 30 and 10 ng/ml for cortisol and 6beta-OHF, respectively. A single dermal dose of DEET alone and in combination with permethrin significantly increased urinary excretion of 6beta-hydroxycortisol 24 h after dosing. Permethrin did not significantly alter the urinary excretion of 6beta-hydroxycortisol. These results indicate that DEET, alone and in combination with permethrin, increased urinary excretion of 6beta-OHF in rats following a single dermal dose application.

Lack of gender differences and large intrasubject variability in cytochrome P450 activity measured by phenotyping with dextromethorphan

Gender-based differences in cytochrome P450 (CYP) activity may occur due to endogenous hormonal fluctuations with the menstrual cycle, which are altered by oral contraceptives. This study assessed the average activity and within-subject variability in CYP3A4 and CYP2D6 in men, women taking Triphasil, and regularly menstruating women not receiving oral contraceptives. Thirty-three healthy volunteers participated in this 28-day pilot study (12 women receiving Triphasil) (OCs), 11 regularly menstruating women not on exogenous progesterone or estrogen (no OCs), and 10 men. CYP3A4 and CYP2D6 activities were phenotyped with dextromethorphan (DM) on study days 7, 14, 21, and 28 using urinary ratios of DM:3-methoxymorphinan (3MM) and DM:dextrorphan (DX), respectively. Serial blood concentrations of estrogen and progesterone and menstrual diaries were used to determine menstrual phase in both groups of women. Average urinary DM:3MM and DM:DX in the 28 extensive metabolizers of CYP2D6 did not differ between the three study populations (p = 0.86 and 0.93, respectively). Post hoc power analysis indicated that more than 1000 subjects would be needed for 80% power (alpha = 0.05) to detect a +/- 15% difference from the population mean in the urinary ratios of dextromethorphan and its metabolites 3MM and DX. Variability in CYP3A4 and CYP2D6 activity, characterized by intrasubject standard deviation, also did not differ. The varying doses of levonorgesterol and ethinyl estradiol in Triphasil, fluctuations in estrogen and progesterone, and menstrual phase did not influence CYP3A4 or CYP2D6 activity. It was concluded that CYP3A4 and CYP2D6 activity and intrasubject variability were not different in the three study populations, and thus a clinically important difference between men, women on Triphasil, and women not receiving oral contraceptives is unlikely. High inter- and intrasubject variability in DM:3MM and DM:DX were clearly demonstrated and limit the use of dextromethorphan to phenotype endogenous CYP3A4 and CYP2D6 activity.