Basic Information
ID DDInter315 and DDInter692
Interaction RECOMMENDED: The effectiveness of estrogen-containing oral contraceptives may be impaired by concomitant treatment with antimicrobial agents. The non-hormonal placebo pills included in some oral contraceptive preparations may contain iron, usually ferrous fumarate. Concomitant administration of these iron pills may significantly decrease the gastrointestinal absorption of antibiotics such as cefdinir. The proposed mechanism is chelation of cefdinir by the iron cation, forming a complex that is poorly absorbed from the gastrointestinal tract.
Management Until further data are available, women using oral contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant antimicrobial therapy. Alternative or additional methods of birth control should be considered during and for at least one week beyond the last dose of short-term antimicrobial therapy, and for at least the initial weeks of long-term antimicrobial therapy when risk may be the greatest.To minimize potential interaction with iron, the product labeling recommends that cefdinir be taken at least 2 hours before or 2 hours after administration of iron-containing products.
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Alternative for Cefdinir -
Alternative for Ethinylestradiol G03A
Desogestrel Norgestimate Norethisterone Drospirenone Etynodiol Levonorgestrel
Etonogestrel Norgestrel Medroxyprogesterone acetate Dienogest Estetrol
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Potential Metabolism Interactions
Substrate-Substrate Interaction：If more than one drug is metabolized by the same CYP, it is possible that its metabolism is inhibited because of the competition between the drugs. That means, it can be useful to lower the dosage of the drugs in the drug-cocktail because they remain longer in the organism than in monotherapy.
Inhibitor-Inhibitor Interaction：Combining two or more inhibitors of one CYP, should be compensated by lowering the dosage of these drugs because the metabolism is reduced and the drugs remain longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.
Inhibitor-Substrate Interaction：Combining drugs that have inhibitory effect and are substrates of one particular CYP, should be compensated by lowering the dosage. They rest longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.