Phenytoin Dextromethorphan

D6 Debrisoquine, sparteine, bufuralol, propanolol, thioridazine, quinidine, phenytoin, fluoxetine NNK3 Dextromethorphan, [bufuralol (4 -OH)... 

Noninterfering acetaminophen, aspirin, amitriptyline, huprenorphine, caffeine, carba-mazepine, chlorpromazine, desipramine, dextromethorphan, doxepin, ephedrine, fenfluramine, imipramine, lidocaine, loxapine, meperidine, methadone, methaqualone, naloxone, naltrexone, nicotine, orphenadrine, oxycodone, papaverine, pentazocine, phendimetra-zine, phenmetrazine, phentermine, phenylpropanolamine, phenytoin, primidone, procaine, promethazine, propoxyphene, propyphenazone, theobromine, theophylline, trazodone, triflupromazine, trimethoprim, trimipramine... 

Noninterfering amitriptyline, amphetamine, atropine, benzoylecgonine, benztropine, caffeine, carbamazepine, carisoprodol, chlorpheniramine, chlorpromazine, chlorprothixene, cimetidine, cocaine, codeine, dextromethorphan, diazepam, diphenhydramine, diphenox-ilate, disopyramide, doxepin, dojylamine, emetine, erythromycin, flurazepam, gluteth-imide, hydrocortisone, hydromorphone, hydroxyzine, imipramine, lidocaine, loxapine, meperidine, meprobamate, methadone, methamphetamine, methapyrilene, methaqualone, methocarbamol, methylphenidate, nicotine, nordiazepam, nortriptyline, orphenadrine, papaverine, pentazocine, phenacetin, phencyclidine, phenmetrazine, phenolphthalein, phentermine, phenylpropanolamine, phenytoin, prazepam, procaineimide, procaine, propoxyphene, propranolol, protriptyline, pseudoephediine, pyrilamine, quinine, salicylam-ide, spironolactone, strychnine, terpin hydrate, thioridazine, thiothixene, triamterene, trifluoperazine, triflupromeizine, trihexyphenidyl, trimeprazine, trimethobenzamide, trimethoprim, tripeleimamine... 

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. 

Dextromethorphan appears not to affect the serum levels of phenytoin. 

A double-blind, crossover study in 4 epileptic patients with severe complex partial seizures found that dextromethorphan 120 mg daily in liquid form (Delsym) over 3 months had no effect on their serum phenytoin levels. There was a non-significant alteration in the complex partial seizure and tonic-clonic seizure frequency. ... 

Romanyshjm, L.A. Wichmann, J.K. Kucharczyk, N. Shumaker, R.C. Ward, D. Sofia, R.D. Simultaneous determination of felbamate, primidone, phenobarbital, carbamazepine, two carbamazepine metabolites, phenytoin, and one phenytoin metabolite in human plasma by hig -performance liquid chromatography. Ther.Drug Monit., 1994,16,90-99 [plasma extracted metabolites, felbamate, phenobarbital, primidone column temp 40-50 LOQ 195-391 ng/mL simultaneous acetaminophen, aspirin, brompheniramine, caffeine, chlorpheniramine, dextromethorphan, dimethadione, ethosuximide, ethotoin, ibuprofen, iministUbene, mephenytoin, mephobarbital, metharbital, methsuximide, para-methadione, phenacemide, phensuximide, phenylpropanolamine, theophylline, trimethadione noninterfering clonazepam valproic acid]... 

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