Phenytoin methadone

Efavirenz inhibits the plasma levels of indinavir, saquinavir and amprenavir and increases the concentrations of ritonavir and nelfinavir. It also lowers the plasma levels of methadone, phenytoin, carbamazepine and phenobarbital. Drugs that stimulate the cytochrome P-450 system will increase its clearance and should not be coadministered. 

Methadone Phenytoin Reduced effect of methadone Increased metabolism... 

Rifamycin is found to afford induction of the specific hepatic drug-metabolizing enzyme system and, therefore, accelerates the metabolism of digitoxin, methadone, phenytoin, 3-blockers, verapamil, oral contraceptives, chloramphenicol, theophylline, besides—oral anticoagulants, estrogens, tolbutamide, barbiturates and itself... 

Codeine, hydrocodone, morphine, methadone, and oxycodone are substrates of the cytochrome P-450 isoenzyme CYP2D6.47 Inhibition of CYP2D6 results in decreased analgesia of codeine and hydrocodone due to decreased conversion to the active metabolites (e.g., morphine and hydromorphone, respectively) and increased effects of morphine, methadone, and oxycodone. Methadone is also a substrate of CYP3A4, and its metabolism is increased by phenytoin and decreased by cimetidine. CNS depressants may potentiate the sedative effects of opiates. 

Phenytoin Similar to phenobarbital may need to increase methadone dose when phenytoin is added to a methadone maintenance drug regimen to avoid withdrawal symptoms. 

Drugs that may be affected by SSRIs Drugs that may be affected by SSRIs include alcohol, benzodiazepines, beta blockers, buspirone, carbamazepine, cisapride, clozapine, cyclosporine, diltiazem, digoxin, haloperidol, hydantoins, lithium, methadone, mexiletine, nonsedating antihistamines, NSAIDs, olanzapine, phenothiazines, phenytoin, pimozide, procyclidine, ritonavir, ropivacaine, sumatriptan, sulfonylureas, sympathomimetics, tacrine, theophylline, tolbutamide, tricyclic antidepressants, and warfarin. 

Drugs that may affect nelfinavir include anticonvulsants, azithromycin, azole antifungals, efavirenz, delavirdine, HMG-CoA reductase inhibitors, indinavir, interleukins, nevirapine, rifabutin, rifampin, ritonavir, saquinavir, St. John s wort. Drugs that may be affected by nelfinavir include amiodarone, antiarrhythmics (amiodarone, quinidine), azithromycin, benzodiazepines, efavirenz, ergot alkaloids, delavirdine, didanosine, fentanyl, indinavir, lamivudine methadone, nonsedating antihistamines, oral contraceptives, phenytoin, pimozide, quinidine, rifabutin, saquinavir, sildenafil, sirolimus, tacrolimus, zidovudine. 

Drugs that may affect zidovudine include acetaminophen, atovaquone, bone marrow suppressive/cytotoxic agents (eg, adriamycin, dapsone), clarithromycin, doxorubicin, fluconazole, ganciclovir, methadone, nelfinavir/ritonavir, phenytoin, probenecid, ribavirin, rifamycins, stavudine, trimethoprim, and valproic acid. 

St. John s wort, rifamycins, and ritonavir. Drugs that may be affected by efavirenz include phenytoin, phenobarbital, carbamazepine, itraconazole, ketoconazole, methadone, ritonavir, amprenavir, benzodiazepines, clarithromycin, ethinyl estradiol, indinavir, nelfinavir, saquinavir, and warfarin. 

T effects OF amiodarone, astemizole, atorvastadn, barbiturates, bepridil, bupropion, cerivastatin, cisapride, clorazepate, clozapine, clarithromycin, desipramine, diazepam, encainide, ergot alkaloids, estazolam, flecainide, flurazepam, indinavir, ketoconazole, lovastatin, meperidine, midazolam, nelfinavir, phenytoin, pimozide, piroxicam, propafenone, propoxyphene, quinidine, rifabutin, saquinavir, sildenafil, simvastatin, SSRIs, TCAs, terfenadine, triazolam, troleandomycin, zolpidem X effects W/ barbiturates, carbamazepine, phenytoin, rifabutin, rifampin, St. John s wort, tobacco X effects OF didanosine, hypnotics, methadone, OCPs, sedatives, theophylline, warfarin EMS T Effects of amiodarone, diazepam, midazolam and BBs, may need X- doses concurrent use of Viagra-type drugs can lead to hypotension X- effects of warfarin concurrent EtOH use can T adverse effects T glucose ODs May cause an extension of adverse SEs symptomatic and supportive Rivasrigmine (Exelon) [Cholinesterase Inhibitor/Anri ... 

There are many drugs that increase the rate of the liver s metabolism. More commonly used medications that fall into this category include rifampin, which is used to treat tuberculosis, and dilantin, phenytoin, and carbamazepine, which are medications commonly used to treat seizures and epilepsy. Chronic alcohol abuse also speeds up the metabolism of the liver. Since all of these substances cause the liver to break down methadone faster then it normally would, one way to correct the problem would be to increase the dose of methadone or break down the dose into several smaller doses given throughout the day. This should only be done on a physician s advice. 

A4 Acetaminophen, alfentanil, amiodarone, astemizole, cocaine, cortisol, cyclosporine, dapsone, diazepam, dihydroergotamine, dihydropyridines, diltiazem, ethinyl estradiol, gestodene, indinavir, lidocaine, lovastatin, macrolides, methadone, miconazole, midazolam, mifepristone (RU 486), paclitaxel, progesterone, quinidine, rapamycin, ritonavir, saquinavir, spironolactone, sulfamethoxazole, sufentanil, tacrolimus, tamoxifen, terfenadine, testosterone, tetrahydro-cannabinol, triazolam, troleandomycin, verapamil Barbiturates, carbamazepine, macrolides, glucocorticoids, pioglitazone, phenytoin, rifampin Erythromycin, 613-hydroxy cortisol... 

Methadone Hydrochloride Visual incompatibilities of methadone hydrochloride were observed with solutions of aminophylline, ammonium chloride, amylo-barbitone sodium, chlorothiazide sodium, heparin sodium, nitrofurantoin sodium, novobiocin, pentobarbitone sodium, phenobarbitone sodium, phenytoin sodium, quinalbarbitone sodium, sodium bicarbonate, sodium iodide, sulfadiazine sodium, sulfafurazole diethanolamine, or thiopentone sodium. 

Interactions are similar to those of opioid analgesics. Methadone has interactions with enzyme inducers. Withdrawal symptoms of methadone are observed upon concurrent administration with phenobarbitone, phenytoin, and rifampicin. Methadone toxicity increases if administered with cimetidine and fluvoxamine. 

Enzyme-inducing drugs, such as carbamazepine, pheno-barbital, phenytoin, and rifampicin, enhance the metabolism of methadone, leading to lower serum methadone concentrations (58). 

PHENYTOIN ANALGESICS-OPIOIDS 1.1 efficacy of fentanyl and methadone 2. Risk of pethidine toxicity 1. t hepatic metabolism of fentanyl and methadone, and possibly an effect at the opioid receptor 2. Phenytoin induces metabolism of pethidine, which causes t levels of a neurotoxic metabolite 1. Be aware that the dose of fentanyl and methadone may need to be t 2. Co-administer with caution the effect may be 1 by administering pethidine intravenously... 

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