<ul>
	<li>Interactions between ethinyloestradiol and other drugs may lead to decreased or increased ethinyloestradiol concentrations, respectively. Decreased ethinyloestradiol serum concentrations may cause an increased incidence of breakthrough bleeding and menstrual irregularities and may possibly reduce efficacy of the oral contraceptive. Example of substances that may decrease serum ethinyloestradiol concentrations include rifampicin, phenytoin, primidone, rifabutin, dexamethasone, griseofulvin, topiramate, some protease inhibitors, modafinil, ritonavir and barbiturates.</li>
	<li>Certain antibiotics including ampicillin, other penicillins and tetracyclines may reduce the efficacy of oral contraceptives.</li>
	<li>During concomitant use of Gestodene &amp; Ehinylestradiol &amp; other drugs that may lead to decreased ethinyloestradiol serum concentrations, it is recommended that a non hormonal back-up method of contraception to be used in addition to the regular intake of this pill.</li>
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