ORAL CONTRACEPTIVE EFFICACY ASSOCIATED WITH THE USE OF ANTIBfOTICS
Keywords:
anti-bacterial agents, contraceptives, oral, Drug interactions, efficacyAbstract
Since the introduction of oral contraceptives in 1961, there was a tendency to reduce estrogen concentrations in order to decrease side effects. This reduction may decrease contraceptive efficacy when combined with antibiotics, Taking into account the existence of divergences between scientific studies, technical manuals from laboratories and the widespread use of oral contraceptives as an efficacious
contraceptive method, the objective of this study was to review clinical reports and pharmacokinetic researches that study the relationship between the use of oral contracepüves and anübiotics and the evidence or not of therapeutic failure. The research was conducted by searching Lilacs and Medline. Thirty-one studies
were selected according to the adopted criterion. Of these, 18 were pharmacokinetic, where 13 did not support the hypothesis that antibiotics decrease contraceptive efficacy (doses above 20mcg), with the exception of rifampicin. Two studies reported a reduction in the plasma concentration of ethinyl
estradiol and another two reported increased excretion and reduced half-life. The reports were considered invalid by some authors and not supported by
pharmacokinetics. Pharmacokinetic researches concluded that rifampicin reduces contraceptive efficacy. Even though pharmacokineüc studies with other antibíotics have not supported a loss in efficacy, some authors postulate the existence of a subgroup of women with higher risk for contraceptive failure. Since it is not possible to idenüfy them and given the serious consequences of an undesired pregnancy, we advise that another contraceptive method be used.
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References
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