indication

For the relief of anxiety, tension, and apprehension, also used as an anticonvulsant for the treatment of epilepsy.

pharmacology

Methylphenobarbital, a barbiturate, is used in combination with acetaminophen or aspirin and caffeine for its sedative and relaxant effects in the treatment of tension headaches, migraines, and pain. Barbiturates act as nonselective depressants of the central nervous system (CNS), capable of producing all levels of CNS mood alteration from excitation to mild sedation, hypnosis, and deep coma. In sufficiently high therapeutic doses, barbiturates induce anesthesia.

mechanism of action

Methylphenobarbital binds at a distinct binding site associated with a Cl^- ionopore at the GABA_A receptor, increasing the duration of time for which the Cl^- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged.

biotransformation

Hepatic, primarily by the hepatic microsomal enzyme system. About 75% of a single oral dose of mephobarbital is metabolized to phenobarbital in 24 hours.

absorption

Approximately 50% of an oral dose of mephobarbital is absorbed from the gastrointestinal tract.

half life

34 (range 11-67) hours

drug interactions

Aminophylline: The barbiturate, methylphenobarbital, decreases the effect of aminophylline.

Betamethasone: The barbiturate, methylphenobarbital, may decrease the effect of the corticosteroid, betamethasone.

Clomifene: The enzyme inducer, methylphenobarbital, decreases the effect of the hormone agent, clomifene.

Conjugated Estrogens: The enzyme inducer, methylphenobarbital, decreases the effect of the hormone agent, conjugated estrogens.

Cyclosporine: The barbiturate, methylphenobarbital, increases the effect of cyclosporine.

Delavirdine: The anticonvulsant, methylphenobarbital, decreases the effect of delavirdine.

Dexamethasone: The barbiturate, methylphenobarbital, may decrease the effect of the corticosteroid, dexamethasone.

Diethylstilbestrol: The enzyme inducer, methylphenobarbital, decreases the effect of the hormone agent, diethylstilbestrol.

Doxycycline: The anticonvulsant, methylphenobarbital, decreases the effect of doxycycline.

Estradiol: The enzyme inducer, methylphenobarbital, decreases the effect of the hormone agent, estradiol.

Ethinyl Estradiol: This product may cause a slight decrease of contraceptive effect

Felodipine: The barbiturate, methylphenobarbital, decreases the effect of felodipine.

Fludrocortisone: The barbiturate, methylphenobarbital, may decrease the effect of the corticosteroid, fludrocortisone.

Folic Acid: Folic acid decreases the effect of anticonvulsant, methylphenobarbital.

Gefitinib: The CYP3A4 inducer, methylphenobarbital, may decrease the serum concentration and therapeutic effects of gefitinib.

Griseofulvin: The barbiturate, methylphenobarbital, decreases the effect of griseofulvin.

Hydrocortisone: The barbiturate, methylphenobarbital, may decrease the effect of the corticosteroid, hydrocortisone.

Levonorgestrel: Phenobarbital decreases the effect of levonorgestrel

Medroxyprogesterone: The enzyme inducer, methylphenobarbital, decreases the effect of the hormone agent, medroxyprogesterone.

Megestrol: The enzyme inducer, methylphenobarbital, decreases the effect of the hormone agent, megestrol.

Methadone: The barbiturate, methylphenobarbital, decreases the effect of methadone.

Metronidazole: The barbiturate, methylphenobarbital, decreases the effect of metronidazole.

Nifedipine: The barbiturate, methylphenobarbital, decreases the effect of the calcium channel blocker, nifedipine.

Norethindrone: This product may cause a slight decrease of contraceptive effect

Oxtriphylline: The barbiturate, methylphenobarbital, decreases the effect of oxtriphylline.

Prednisolone: The barbiturate, methylphenobarbital, may decrease the effect of the corticosteroid, prednisolone.

Prednisone: The barbiturate, methylphenobarbital, may decrease the effect of the corticosteroid, prednisone.

Quinidine: The anticonvulsant, methylphenobarbital, decreases the effect of quinidine.

Theophylline: The barbiturate, methylphenobarbital, decreases the effect of theophylline.

Triamcinolone: The barbiturate, methylphenobarbital, may decrease the effect of the corticosteroid, triamcinolone.

Verapamil: Methylphenobarbital, a CYP3A4 inducer, may increase the serum concentration of Verapamil, a CYP3A4 substrate. Monitor for changes in the therapeutic/adverse effects of Verapamil if Methylphenobarbital is initiated, discontinued or dose changed.