Parecoxib Phenytoin

NS AIDs ANTIEPILEPTICS 1. Parecoxib levels may be 1 by carbamazepine and phenytoin 2. Report of T phenytoin levels when celecoxib added 1. Carbamazepine and phenytoin induce CYP3A4-mediated metabolism of parecoxib 2. Uncertain possibly competitive inhibition of CYP2C9-mediated metabolism of phenytoin 1. Watch for poor response to parecoxib 2. Monitor phenytoin levels... 

Induction of hepatic metabolism 2. Inhibition of phenytoin metabolism (parecoxib - CYP2C9 calcium channel blockers -CYP3A4 mianserin -unknown) 3. Uncertain amiodarone inhibits CYP2C9, which plays a role in phenytoin metabolism and inhibits Intestinal P-gp, which may t bioavailability of phenytoin. Theophylline i absorption of phenytoin... 

Enzyme inducers. The effects of the enzyme inducers carbamazepine, dexamethasone, phenytoin and rifampicin have not been studied with parecoxib. Nevertheless, the manufacturer of parecoxib warns that they may increase the metabolism of valdecoxib. ... 

As parecoxib is rapidly metabolised to valdecoxib, the interactions are usually considered to be due to the effects of valdecoxib. The manufacturer of parecoxib cautions the concurrent use with carbamazepine, dexamethasone and rifampicin as their effects on parecoxib have not been studied. Valdecoxib increases the levels of dextromethorphan and omeprazole. Because of these interactions, caution is advised with drugs that are metabolised by the same isoenzymes, nameiy flecainide, metoprolol, propafenone, omeprazoie, diazepam, imipramine and phenytoin. No interaction appears to occur between parecoxib and midazolam. 

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