Oral contraceptives hormonal interactions

Saw palmetto (cabbage palm, fan palm, scrub palm) Serenoa repens %mptoms of benign prostatic hyperplasia Generally well-tolerated occasional gastrointestinal effects May interact with hormones such as oral contraceptive drugs and hormone replacement therapy. 

Prescribers are advised to consult the package insert of any medication administered concomitantly with hormonal contraceptives, because some medications may decrease the effectiveness of these birth control products. Patients should be prospectively cautioned not to self-medicate with the herbal supplement St. John s wort because a possible interaction has been suggested with hormonal contraceptives based on reports of breakthrough bleeding while on oral contraceptives shortly after starting St. John s wort. Pregnancies have been reported by users of combined hormonal contraceptives who also used some form of St. John s wort. 

While numerous studies have evaluated the effect of oral contraceptives and postmenopausal hormone replacement on drug clearance, many were flawed by poor study design. Table 21.1 lists studies that were of crossover or sequential design such that each subject was evaluated in the contraceptive phase and placebo phase. These study designs minimize the effect of interindividual variability. In most studies there was no effect of hormonal therapy on drug metabolism, but in some there were interactions that inhibited or increased the metabolism of concurrently administered drugs. 

Kovacs L, Somos P, Hamori M. Examination of the potential interaction between ketoconazole (Nizoral) and oral contraceptives with special regard to products of low hormone content (Rigevidon, Anteovin). Ther Hung 1986 34 167. 

Clinically important, potentially hazardous interactions with aluminium hydroxide, antacids, charcoal, cholestyramine, colestimide, colestipol, cyclosporine, cytochrome P4503A substrates, dapsone, estrogenic hormones, nitrendipine, oral contraceptives... 

Rifampin s potent induction of hepatic enzymes, especially cytochrome P450 (CYP) 3A4, may enhance the ehmination of many other drugs, most notably the protease inhibitors used to treat HIV (Table 110-7). HIV-positive patients may beneht from the use of rifabutin instead of rifampin (see below). ° Also, women who use oral contraceptives must use another form of contraception during therapy because increased clearance of the hormones may lead to unexpected pregnancies. Patient records should be reviewed for potential drug interactions before dispensing rifampin. Rifampin may turn urine and other secretions orange-red and may permanently stain some types of contact lenses. 

May interact with hormones such as oral contraceptive drugs and hormone replacement therapy. 

Oral or topical contraceptive hormone products interact with antibiotics, not pseudoephedrine. 

Co-cyprindiol is a mixture of the anti-androgenic progestogen, cyproter-one acetate 2 mg, with ethinylestradiol 35 micrograms. It is used for the treatment of acne and moderately severe hirsutism in women who may also wish to use it as an oral contraceptive, and its contraceptive efficacy is expected to be reduced by the same hepatic enzyme inducers (see Table 28. r, (p.975)) that interact with conventional combined oral contraceptives. The precautions described in this section for the combined hormonal contraceptives with the various drugs listed in Table 28.1 , (p.975), should therefore be followed, see Hormonal contraceptives + Antiepileptics Barbiturates or Phenytoin , p.985. 

For a discussion of the adverse hepatic interaction between oral contraceptives and the maerolide troleandomycin, see Hormonal contraceptives orFlRT + Antibaeterials Troleandomycin , p.984. 

The interaction between metronidazole and combined oral contraceptives is not established, and the whole issue of any interaction with broad-spectrum antibacterials remains very controversial. Bearing in mind the extremely wide use of both metronidazole and combined oral contraceptives, any increased incidence of contraceptive failure above that seen in general usage is clearly very low indeed. The Faculty of Family Planning and Reproductive Health Care (FFPRHC) Clinical Effectiveness Unit has issued guidance on the use of antibacterials with combined hormonal contraceptives. Although they recognise that there is poor evidence for contraceptive failure, they recommend that additional form of contraception, such as condoms, should be used for short courses of antibacterials, see Hormonal contraceptives + Antibacterials Penicillins , p.981, for more detailed information. This applies to both the oral and the patch form of the combined contraceptive. This advice has usually been applied to only broad-spectrum antibacterials that do not induce liver enzymes but the FFPRHC notes that some confusion has occurred over which antibacterials are considered to be broad-spectrum , and thus they recommend that this advice is applied to all antibacterials that do not induce liver enzymes, which would include metronidazole. ... 

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