Tegretol

Tegretol Drug Interactions

carbamazepine

Manufacturer:

Novartis

Distributor:

DKSH
Full Prescribing Info
Drug Interactions
Cytochrome P450 3A4 (CYP3A4) is the main enzyme catalyzing formation of the active metabolite carbamazepine-10,11-epoxide. Co-administration of inhibitors of CYP3A4 may result in increased carbamazepine plasma concentrations which could induce adverse reactions. Co-administration of CYP3A4 inducers might increase the rate of carbamazepine metabolism, thus leading to potential decreases in the carbamazepine serum level and therapeutic effect. Similarly, discontinuation of a CYP3A4 inducer may decrease the rate of metabolism of carbamazepine, leading to an increase in carbamazepine plasma levels.
Carbamazepine is a potent inducer of CYP3A4 and other phase I and phase II enzyme systems in the liver, and may therefore reduce plasma concentrations of co-medications mainly metabolized by CYP3A4 by induction of their metabolism.
Human microsomal epoxide hydrolase has been identified as the enzyme responsible for the formation of the 10,11-transdiol derivative from carbamazepine-10,11-epoxide. Co-administration of inhibitors of human microsomal epoxide hydrolase may result in increased carbamazepine-10,11-epoxide plasma concentrations.
Interactions resulting in a contraindication: The use of Tegretol is contraindicated in combination with monoamine-oxidase inhibitors (MAOIs); before administering Tegretol MAOIs should be discontinued for a minimum of 2 weeks, or longer if the clinical situation permits (see CONTRAINDICATIONS).
Agents that may raise carbamazepine plasma levels: Since raised plasma carbamazepine levels may result in adverse reactions (e.g. dizziness, drowsiness, ataxia, diplopia), the dosage of Tegretol should be adjusted accordingly and/or the plasma levels monitored when used concomitantly with the substances described as follows: Analgesics, anti-inflammatory drugs: dextropropoxyphene, ibuprofen.
Androgens: danazol.
Antibiotics: macrolide antibiotics (e.g. erythromycin, troleandomycin, josamycin, clarithromycin), ciprofloxacine.
Antidepressants: possibly desipramine, fluoxetine, fluvoxamine, nefazodone, paroxetine, trazodone, viloxazine.
Antiepileptics: stiripentol, vigabatrin.
Antifungals: azoles (e.g. itraconazole, ketoconazole, fluconazole, voriconazole). Alternative anti-convulsants may be recommended in patients treated with voriconazole or itraconazole.
Antihistamines: loratadine, terfenadine.
Antipsychotics: olanzapine.
Antituberculosis: isoniazid.
Antivirals: protease inhibitors for HIV treatment (e.g. ritonavir).
Carbonic anhydrase inhibitors: acetazolamide.
Cardiovascular drugs: diltiazem, verapamil.
Gastrointestinal drugs: possibly cimetidine, omeprazole.
Muscle relaxants: oxybutynin, dantrolene.
Platelet aggregation inhibitors: ticlopidine.
Other interactions: grapefruit juice, nicotinamide (only in high dosage).
Agents that may raise the active metabolite carbamazepine-10,11-epoxide plasma levels: Since raised plasma carbamazepine-10,11-epoxide levels may result in adverse reactions (e.g. dizziness, drowsiness, ataxia, diplopia), the dosage of Tegretol should be adjusted accordingly and/or the plasma levels monitored when used concomitantly with the substances described as follows: Loxapine, quetiapine, primidone, progabide, valproic acid, valnoctamide and valpromide.
Agents that may decrease carbamazepine plasma levels: The dose of Tegretol may have to be adjusted when used concomitantly with the substances described as follows: Antiepileptics: felbamate, methsuximide, oxcarbazepine, phenobarbital, phensuximide, phenytoin (to avoid phenytoin intoxication and subtherapeutic concentrations of carbamazepine it is recommended to adjust the plasma concentration of phenytoin to 13 micrograms/mL before adding carbamazepine to the treatment) and fosphenytoin, primidone, and, although the data are partly contradictory, possibly also clonazepam.
Antineoplastics: cisplatin or doxorubicin.
Antituberculosis: rifampicin.
Bronchodilatators or anti-asthma drugs: theophylline, aminophylline.
Dermatological drugs: isotretinoin.
Other interactions: herbal preparations containing St John's wort (Hypericum perforatum).
Effect of Tegretol on plasma levels of concomitant agents: Carbamazepine may lower the plasma level, or diminish - or even abolish - the activity of certain drugs. The dosage of the following drugs may have to be adjusted to clinical requirements: Analgesics, anti-inflammatory agents: buprenorphine, methadone, paracetamol (long term administration of carbamazepine and paracetamol (acetaminophen) may be associated with hepatotoxicity), phenazone (antipyrine), tramadol.
Antibiotics: doxycycline, rifabutin.
Anticoagulants: oral anticoagulants (e.g. warfarin, phenprocoumon, dicoumarol, acenocoumarol, rivaroxaban, dabigatran, apixaban, edoxaban).
Antidepressants: bupropion, citalopram, mianserin, nefazodone, sertraline, trazodone, tricyclic antidepressants (e.g. imipramine, amitriptyline, nortriptyline, clomipramine).
Antiemetics: aprepitant.
Antiepileptics: clobazam, clonazepam, ethosuximide, felbamate, lamotrigine, eslicarbazepine, oxcarbazepine, primidone, tiagabine, topiramate, valproic acid, zonisamide. To avoid phenytoin intoxication and subtherapeutic concentrations of carbamazepine it is recommended to adjust the plasma concentration of phenytoin to 13 micrograms/mL before adding carbamazepine to the treatment. There have been rare reports of an increase in plasma mephenytoin levels.
Antifungals: itraconazole, voriconazole. Alternative anti-convulsants may be recommended in patients treated with voriconazole or itraconazole.
Antihelmintics: praziquantel, albendazole.
Antineoplastics: imatinib, cyclophosphamide, lapatinib, temsirolimus.
Antipsychotics: clozapine, haloperidol and bromperidol, olanzapine, quetiapine, risperidone, ziprasidone, aripiprazole, paliperidone.
Antivirals: protease inhibitors for HIV treatment (e.g. indinavir, ritonavir, saquinavir).
Anxiolytics: alprazolam, midazolam.
Bronchodilatators or anti-asthma drugs: theophylline.
Contraceptives: hormonal contraceptives (alternative contraceptive methods should be considered).
Cardiovascular drugs: calcium channel blockers (dihydropyridine group) e.g. felodipine, digoxin, simvastatin, atorvastatin, lovastatin, cerivastatin, ivabradine.
Corticosteroids: corticosteroids (e.g. prednisolone, dexamethasone).
Drugs used in erectile dysfunction: tadalafil.
Immunosuppressants: ciclosporin, everolimus, tacrolimus, sirolimus.
Thyroid agents: levothyroxine.
Other drug interactions: products containing oestrogens and/or progesterones.
Combinations that require specific consideration: Concomitant use of carbamazepine and levetiracetam has been reported to increase carbamazepine-induced toxicity.
Concomitant use of carbamazepine and isoniazid has been reported to increase isoniazid-induced hepatotoxicity.
Combined use of carbamazepine and lithium or metoclopramide on the one hand, and carbamazepine and neuroleptics (haloperidol, thioridazine) on the other, may lead to increased neurological adverse reactions (with the latter combination even in the presence of 'therapeutic plasma levels').
Concomitant medication with Tegretol and some diuretics (hydrochlorothiazide, furosemide) may lead to symptomatic hyponatraemia.
Carbamazepine may antagonize the effects of non-depolarizing muscle relaxants (e.g. pancuronium). Their dosage may need to be raised, and patients should be monitored closely for more rapid recovery from neuromuscular blockade than expected.
Carbamazepine, like other psychoactive drugs, may reduce alcohol tolerance. It is therefore advisable for the patient to abstain from alcohol.
Concomitant use of carbamazepine with direct acting oral anti-coagulants (rivaroxaban, dabigatran, apixaban, and edoxaban) may lead to reduced plasma concentrations of direct acting oral anti-coagulants, which carries the risk of thrombosis. Therefore, if a concomitant use is necessary, close monitoring of signs and symptoms of thrombosis is recommended.
Interference with serological testing: Carbamazepine may result in false positive perphenazine concentrations in HPLC analysis due to interference.
Carbamazepine and the 10,11-epoxide metabolite may result in false positive tricyclic antidepressant concentration in fluorescence polarized immunoassay method.
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