Nevirapine is associated with a 30% decrease in contraceptive hormone levels in pharmacokinetic (PK) studies. Adequately powered studies have not previously been conducted to assess clinical outcomes, such as ovulation, in women receiving concomitant oral contraception and nevirapine.
At the 3rd International Workshop on HIV and Women, Kavita Nanda from FHI 360 presented findings from a study comparing ovulation rates in women receiving combined oral contraceptives (COCs) with nevirapine-containing ART and COCs alone.
This was a non-randomised clinical trial of HIV positive women aged 18-35 years who had regular menstruation, were sexually active, and had no medical contraindications to COC use. It was conducted in South Africa and Uganda between June 2009 and May 2011.
The study enrolled 196 women receiving nevirapine-containing ART and 207 women currently ineligible (> 350 cells/mm3) as a COC-only control group. All women received COCs containing 30 mg of ethinyl estradiol and 300 mg of norgestrel. The investigators estimated ovulation weekly serum progesterone (>10 nmol/L was considered presumptive evidence of ovulation) in the first two treatment cycles. Participants took COCs for at least one cycle before their ovulation assessment. They were tested for pregnancy monthly for 24 weeks.
Women were a median of 29 years of age; most women were in the normal range for BMI and had been pregnant before.
The investigators found no statistically significant differences in ovulation rates between the two groups: 26% of the ART and 16% of COC-only groups ovulated in the first cycle; 18% of ART and 19% of COC-only ovulated in the second and 11% of ART and 12% of COC-only ovulated in both cycles. The unadjusted odds ratio (OR) for ovulation in the ART group compared with the COC-only group was 1.4 (95% CI 0.85-2.18), p=0.2.
Women receiving COCs at baseline were 62% less likely to ovulate during follow up, OR 0.38 (0.2-0.7), p=0.002. Older age (29-32 years) halved the likelihood of ovulation, OR 0.51 (0.27-0.98), p=0.04.
There were nine pregnancies in each group, giving pregnancy rates of 10 per 100 woman years (95% CI 5-19) for each group. Women who missed three or more pills in a row were 17 times more likely to get pregnant; OR 16.76 (3.15-89.24), p=0.001. Self reported adherence and condom use did not differ between the two groups.
Adverse events were no different between the groups; three were serious but unrelated to the study medication (malaria, cellulitis and fracture), all in COC-only group.
Dr Nanda also gave a good overview of what is important with drug interactions with contraceptives at this meeting.
Nanda K et al. Nevirapine-containing ART does not reduce combined oral contraceptive effectiveness: results from South Africa and Uganda. 3rd International Workshop on HIV & Women, 14-15 January 2013, Toronto, Canada. Oral abstract O_03.
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