Rifampicin Carbamazepine

CYP2C18/ 2C19 Liver CYP2C19 2 CYP2C19 3 (S)-mephenytoin 4 -hydroxylation (preferred1) Ticlopidine (acceptable1, also inhibits CYP2D6) Ketoconazole Rifampicine Carbamazepine < 5%... 

Association to allopurinol, amiodarone, fluoroquinolones, carbamazepine, pheno-barbital, rifampicin, and others Inhibition of CYP activity by the drugs... 

Theophylline is a narrow therapeutic index drug with significant difference in bioavailability following oral administration. The half-life of the drug is increased by heart failure, cirrhosis and viral infections, in elderly patients, and by certain drugs, such as cimetidine, ciprofloxacin, oral contraceptives and fluvoxamine. The half-life is decreased in smokers, chronic alcoholism, and by certain drugs, such as phenytoin, rifampicin and carbamazepine. 

Rifampicin, the anti-convulsants phenytoin, phe-nobarbitone and carbamazepine, and the steroid dex-amethasone, are amongst the best recognized inducers of enzyme function, and their action nearly... 

Beta-blockers interact with a large number of other medications. The combination of beta-blockers with calcium antagonists should be avoided, given the risk for hypotension and cardiac arrhythmias. Cimetidine, hydralazine, and alcohol all increase blood levels of beta-blockers, whereas rifampicin decreases their concentrations. Beta-blockers may increase blood levels of phenothiazines and other neuroleptics, clonidine, phen-ytoin, anesthetics, lidocaine, epinephrine, monoamine oxidase inhibitors and other antidepressants, benzodiazepines, and thyroxine. Beta-blockers decrease the effects of insulin and oral hypoglycemic agents. Smoking, oral contraceptives, carbamazepine, and nonsteroidal anti-inflammatory analgesics decrease the effects of beta-blockers (Coffey, 1990). 

Carbamazepine, phenytoin, rifampicin. Plasma concentration of theophylline... 

Gynaecology Orai contraceptives Barbiturates, carbamazepine, dichiorai-phenazone, phenytoin, primidone, rifampicin. Reduced effect. 

Cardiac depressant effects may occur when verapamil or diltiazem is combined with a (p-adrenoceptor antagonoist or a cardiac glycoside. Nifedipine and verapamil are metabolised by cytochrome P-450 3A4. Inhibitors of this enzyme, e.g. HIV-protease inhibitors, cimetidine, fluoxetine, ketoconazole, erythromycin, will increase plasma levels and the dose should be carefully monitored. Conversely, enzyme inducers, e.g. carbamazepine, rifampicin, phenytoin, will decrease their plasma concentrations. 

Cyclosporin is metabolised by the hepatic cytochrome P-450 enzyme system, and enzyme induction by phenobarbital, phenytoin, carbamazepine, or rifampicin will drastically increase the clearance of cyclosporin. Concurrent administration of these drugs has caused rejection of transplanted organs. Conversely, the use of enzyme inhibitors, such as erythromycin or the azole antifungal agents, e.g. ketoconazole, will increase the blood concentrations of cyclosporin leading to an increased risk of toxic side effects. 

Ethosuximide Reduces low threshold Ca2+ currents (T-type) Well absorbed orally, with peak levels in 3-7 h not protein-bound completely metabolized to inactive compounds tjy2 typically 40 h Absence seizures Toxicity Nausea, headache, dizziness, hyperactivity Interactions Valproate, phenobarbital, phenytoin, carbamazepine, rifampicin... 

N/V/D, abcl pain, bleeding, fever, T QT Interactions T Effects W/ atazanavir, clar-itliromycin, erythromycin, indinavir, itraconazole, ketoconazole, nefazodone, nelfi-navir, ritonavir, saquinavir, telithromydn 1 effects W/ antacids, carbamazepine, dexamethasone, phenobarbital, phenytoin, rifampicin, St. John s wort EMS Ding contains lactose, may cause D/abd discomfort in pts w/ lactose intolerance OD Sxs unknown symptomatic and supportive... 

Isoniazid can cause convulsions and therefore should be prescribed with caution in patients with epilepsy. Isoniazid is an enzyme inhibitor and may increase carbamazepine levels. Rifampicin is an enzyme inducer and may decrease carbamazepine levels. 

Rifampicin is an enzyme inducer and can increase the incidence and severity of isoniazid-induced hepatitis. Carbamazepine is an enzyme induction agent and interacts with isoniazid, increasing its hepatotoxicity. Isoniazid toxicity is associated with fast acetylator genotype. Although his phenotype was unknown, the interaction with carbamazepine increases risk of this toxicity. 

Acceleration of hepatic coumarin metabolism enzyme induction, e.g., by carbamazepine, rifampicin ... 

The effects of rifampicin on the pharmacokinetics and pharmacodynamics of buspirone were investigated in 10 young healthy volunteers. There was a significant reduction in the effects of buspirone in three of the six psychomotor tests used after rifampicin pretreatment. The interaction between rifampicin and buspirone is probably mostly due to increased CYP3A4 activity. Buspirone will most likely have a greatly reduced anxiolytic effect when it is used together with rifampicin or other potent inducers of CYP3A4, such as phenytoin and carbamazepine... 

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

ALMOTRIPTAN, ELETRIPTAN CARBAMAZEPINE Possible 1 plasma concentrations of almotriptan and risk of inadequate therapeutic efficacy. Risk of serotonin syndrome One of the major metabolizing enzymes of almotriptan - CYP3A4 isoenzymes - is induced by rifampicin. As there are alternative metabolic pathways, the effect may not be significant and can vary from individual to individual. Triptans and carbamazepine are both stimulants of 5-HT receptors, and carbamazepine in addition prevents the reuptake of 5-HT Be aware of possibility of l response to triptan, and consider T dose if considered to be due to interaction. Be aware of the possibility of the occurrence of serotonin syndrome >- For signs and symptoms of serotonin toxicity, see Clinical Features of Some Adverse Drug Interactions, Serotonin toxicity and serotonin syndrome... 

ZALEPLON, ZOLPIDEM, ZOPICLONE ANTI EPILEPTICS-CARBAMAZEPINE, RIFAMPICIN i levels of these hypnotics Induction of CYP3A4-mediated metabolism Watch for poor response to these agents... 

MODAFINIL CARBAMAZEPINE, PHENOBARBITONE, RIFAMPICIN 1 plasma concentrations of modafinil with possibility of 1 therapeutic effect Induction of CYP3A4, which has a partial role in the metabolism of modafinil Be aware... 

IFOSFAMIDE 1. ANTIBIOTICS-rifampicin 2. ANTICANCER AND IMMUNOMODULATING DRUGS - dexamethasone 3. ANTIDEPRESSANTS-St John s wort 4. ANTI EPILEPTICS -carbamazepine, phenytoin, phenobarbital t rate of biotransformation to 4-hydroxyifbsfamide, the active metabolite, but there is no change in AUC of 4-hydroxyifosfamide Due to t rate of metabolism and of clearance owing to induction of CYP3A4 and CYP2D6 Be aware - clinical significance may be minimal or none... 

PACLITAXEL 1. ANTIBIOTICS-rifampicin 2. ANTIDEPRESSANTS-St John s wort 3. ANTIEPILEPTICS -carbamazepine, phenobarbital, phenytoin 1 plasma concentration of paclitaxel and 1 efficacy of paclitaxel Due to induction of hepatic metabolism of paclitaxel by the CYP isoenzymes Monitor for clinical efficacy and need to T dose if inadequate response is due to interaction... 

GESTRINONE 1. ANTIBIOTICS-rifampicin 2. ANTIEPILEPTICS-barbiturates, carbamazepine, phenytoin 1 gestrinone levels Induction of metabolism Watch for poor response to gestrinone... 

Several drugs, for example the oral contraceptive pill, viloxazine, thiabendazole, aminoglutethimide, antiepileptics (carbamazepine, phenytoin, barbiturates) and the antibiotic rifampicin decrease plasma concentrations of theophylline. 

Enzyme induction can be problematic with co-administration of benzodiazepines and rifampicin or certain anticonvulsants (phenobarbital, phenytoin, carbamazepine). However, despite enzyme stimulation, the net effect of adding these anticonvulsants can be augmentation of benzodiazepine-induced sedation. 

Serum carbamazepine concentrations were reduced in a 44-year-old woman who also took rifampicin (105), presumably through induction of metaboUsm. 

Drugs that induce liver microsomal enzymes, such as phenobarbital, phenytoin, carbamazepine, rifampicin, and isoniazid, can make paracetamol poisoning more severe (104,105). In patients taking such drugs the serum paracetamol concentration should be doubled before consulting the usual treatment nomogram. 

Sulfonamides, penicillins, diclofenac, oxyphenbutazone, piroxicam, phenytoin, carbamazepine (Same as for erythema multiforme) penicillamine, captopril, piroxicam, penicillins, rifampicin Frusemide, penicillamine, penicillin, PUVA therapy Immunosuppressants, mexiletine, thioridazine, penicillamine, moduretic , atenolol, quinacrine... 

Clinically important, potentially hazardous interactions with atazanavir, carbamazepine, clarithromycin, dexamethasone, erythromycin, indinavir, itraconazole, ketoconazole, nefazodone, nelfinavir, phenobarbital, phenytoin, rifampicin, ritonavir, saquinavir, St John s wort... 

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