Types of combined oral contraceptives used by US women

Effects of ritonavir-boosted protease inhibitors on combined oral contraceptive pharmacokinetics and pharmacodynamics in HIV-positive women

OBJECTIVE

To assess the pharmacokinetics of combined oral contraceptive (COC) components and prevalence of ovulation in HIV-positive women using ritonavir-containing antiretroviral regimens compared to those using regimens previously found not to interact with COCs or not using any antiretrovirals.

STUDY DESIGN

We conducted a prospective cohort pharmacokinetic pilot study comparing the pharmacokinetics of levonorgestrel (LNG) and ethinyl estradiol (EE) in HIV-positive women taking ritonavir-containing antiretroviral regimens to those in women using non-ritonavir-containing regimens or no antiretrovirals. Participants received COCs containing LNG/EE 150/30 mcg for 21 days. Beginning day 21, we collected serial blood samples over 72 h. The primary outcome was area under the curve (AUC) of LNG, with secondary outcomes including other LNG pharmacokinetic measures, EE pharmacokinetics and ovulation as measured by serum progesterone.

RESULTS

Pharmacokinetic parameters of LNG showed a trend toward increased exposure in women on ritonavir. LNG AUClast increased by 32.6% (312±60.9 vs. 243±82.6 ng/mL*h, p=.033, n=5) in women taking ritonavir compared to the control group (n=10). The Cmax (9.68±1.81 vs. 7.62±2.29 ng/mL) and Cmin (4.97±1.15 vs. 3.70±1.29 ng/mL) were also higher in the ritonavir arm. After excluding the inconsistent users (n=2), CL of LNG was reduced in the ritonavir arm (p=.032). EE pharmacokinetic profiles were not different between groups. The progesterone concentrations were similar in women of both groups, and none were consistent with ovulation during the treatment cycle.

CONCLUSION

Women on ritonavir showed an approximately 30% increase in LNG exposure but no difference in EE exposure.

IMPLICATIONS

The current data suggest that ritonavir does not have a clinically significant impact on oral contraceptive pharmacokinetics.

A combined oral contraceptive affects mucosal SHIV susceptibility factors in a pigtail macaque (Macaca nemestrina) model

BACKGROUND

Injectable hormonal contraception may increase women's risk of HIV acquisition and can affect biological risk factors in animal models of HIV. We established, for the first time, a model to investigate whether combined oral contraceptives (COC) alter SHIV susceptibility in macaques.

METHODS

Seven pigtail macaques were administered a monophasic levonorgestrel (LNG)/ethinyl estradiol (EE) COC at 33% or 66% of the human dose for 60 days. Menstrual cycling, vaginal epithelial thickness, and other SHIV susceptibility factors were monitored for a mean of 18 weeks.

RESULTS

Mean vaginal epithelial thicknesses were 290.8 μm at baseline and 186.2 μm during COC (P = 0.0141, Mann-Whitney U-test). Vaginal pH decreased from 8.5 during treatment to 6.5 post-treatment (0.0176 two-tailed t-test). Measured microflora was unchanged.

CONCLUSIONS

COC caused thinning of the vaginal epithelium and vaginal pH changes, which may increase SHIV susceptibility. 0.033 mg LNG + .0066 mg EE appeared effective in suppressing ovulation.