Modafinil Phenytoin

Drugs That Interfere with Hormonal Contraceptives Concomitant use of HIV-protease inhibitors, griseofulvin, modafinil, penicillins, rifampin, rifabutin, phenytoin, carbamazepine, or certain herbal supplements such as St. John s wort with hormonal contraceptive agents may reduce the effectiveness of the contraception and up to one month after discontinuation of these concomitant therapies. Therefore, women requiring treatment with one or more of these drugs must use two other effective or highly effective methods of contraception or abstain from heterosexual sexual contact while taking thalidomide... 

Reduced ethinyl estradiol concentrations have been associated with concomitant use of substances that induce hepatic microsomal enzymes, such as rifampin, rifabutin, barbiturates, phenylbutazone, phenytoin sodium, griseofulvin, topiramate, some protease inhibitors, modafinil, and possibly St. John s wort ... 

PHENYTOIN CNS STIMULANTS-MODAFINIL May 1 modafinil levels Induction of CYP3A4, which has a partial role in the metabolism of modafinil Be aware... 

MODAFINIL 1. ANTIBIOTICS-rifabutin 2. ANTICANCER AND IMMUNOMODULATING DRUGS - corticosteroids 3. ANTIDEPRESSANTS-St John s wort 4. ANTIEPILEPTICS -phenytoin 5. ANTIDIABETIC DRUGS-pioglitazone 6. ANTIVIRALS - efavirenz, nevirapine May 1 modafinil levels Induction of CYP3A4, which has a partial role in the metabolism of modafinil Be aware... 

The manufacturers caution if enzyme-inducing anticonvulsants, particularly phenytoin, are used with modafiniL There is speculation, based on in vitro studies, about some possible interactions with other drugs, such as warfarin. Modafinil is an inducer of CYP3A4 and therefore may be expected to interact with substrates of this isoenzyme. 

Due to the enzyme inhibiting potential of modafinil, the manufacturers say that care should be taken if phenytoin is also given. There is in vitro evidence to indicate that mod nil may possibly inhibit the metabolism of phenytoin by the cytochrome P450 isoenzymes CYP2C9 and CYKCW, and so there is some reason for monitoring concurrent use for evidence of increased phenytoin effects and toxicity... 

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