Antibiotics and oral contraceptives

With the exception of rifampin-like drugs, there is a lack of scientific evidence supporting the ability of commonly prescribed antibiotics, including all those routinely employed in outpatient dentistry, to either reduce blood levels and/or the effectiveness of oral contraceptives. To date, all clinical trials studying the effects of concomitant antibiotic therapy (with the exception of rifampin and rifabutin) have failed to demonstrate an interaction. Like all drugs, oral contraceptives are not 100 per cent effective with the failure rate in the typical United States population reported to be as high as 3 per cent. It is thus possible that the case reports of unintended pregnancies during antibiotic therapy may simply represent the normal failure rate of these drugs. Considering that both drug classes are prescribed frequently to women of childbearing potential, one would expect a much higher rate of oral contraceptive failure in this group of patients if a true drug:drug interaction existed. On the other hand, if the interaction does exist but is a relatively rare event, occurring in, say, 1 in 5000 women, clinical studies such as those described in this article would not detect the interaction. The pharmacokinetic studies of simultaneous antibiotic and oral contraceptive ingestion, and the retrospective studies of pregnancy rates among oral contraceptive users exposed to antibiotics, all suffer from one potential common weakness, i.e., their relatively small sample size. Sample sizes in the pharmacokinetic trials ranged from 7 to 24 participants, whereas the largest retrospective study of pregnancy rates still evaluated less than 800 total contraceptive users. Still, the incidence of such a rare interaction would not differ from the accepted normal failure rate of oral contraceptive therapy. The medico-legal ramifications of what looks like at best a rare interaction remains somewhat "murky." On one hand, we have medico-legal experts advising the profession to exercise caution and warn all oral contraceptive users of a potential reduction in efficacy during antibiotic therapy. These opinions are not evidence-based and rely heavily on one or two legal proceedings that cannot even be substantiated. On the other hand, there is one recently published legal proceeding in which the outcome was in favor of the oral surgeon. There is clearly...

Estudio controlado del efecto de anticonceptivos orales sobre la presión arterial / Controlled study of oral contraceptive effect over arterial pressure

The possible hypertensive effect of oral contraceptives is a controversial issue. We studied 371 women, admitted to the family planning program of a atate funded outpatient clinic, that were followed during 12 months. These women were divided in 4 groups. Group 1 was constituted by 98 women that used intrauterine devices. Group 2 by 98 women taking 30 µg of estrogen and 300 µg of progestogen. Group 3 by 83 women taking 35 µg of estrogen and 500 µg of progestogen and Group 4 by 92 puerperal women taking 30 µg of levonorgestrel, that after six month started to use an intrauterine device (n=35) or the contraceptives of group 2 (n=38) or group 3 (n=19). Age, initial blood pressure and weight were similar in the 4 groups. There was no significant change in blood pressure after 6 or 12 centrations up to 35 µg and progestogen concentrations between 300 and 500 µg do not induced changes in blood pressure

Oral contraceptives: beyond pregnancy prevention, Part 1

Combined oral contraceptives (COC) have become an integral part of birth control. A growing body of knowledge is pointing to several non contraceptive benefits of COCs while illuminating the potential risks of the "pills". Pharmacists have a critical role to play in promoting the safe and effective use of these medications