Biomaterial Database

Interactions of orphenadrine and phenobarbitone with chlorpromazine: plasma concentrations and effects in man. 1975

S Loga, and S Curry, and M Lader

1 Two studies were carried out on acutely psychotic patients receiving chlorpromazine (100 mg) 8-hourly. 2 In the pilot study on five patients, plasma chlorpromazine concentrations fell over the course of 3 weeks of treatment and parallel changes were noted in the plasma half-life of antipyrine, salivation rate and handwriting length. 3 In the main study involving twelve patients treated for 15 weeks, the above findings were confirmed and were interpreted as indicating that chlorpromazine accelerated its own metabolism by inducing liver microsomal oxidising enzymes. No metabolites of chlorpromazine were detected in plasma. 4 The addition of phenobarbitone (50 mg) 8-hourly for 3 weeks, or orphenadrine (100 mg) 8-hourly for 3 weeks, resulted in a lowering of plasma chlorpromazine concentrations together with a further shortening of plasma antipyrine half-life. 5 Physiological effects of the additional treatments suggested that phenobarbitone lessens the effects of chlorpromazine by lowering body concentrations. However, orphenadrine acts more by virtue of its anticholinergic effects. 6 It was concluded that phenobarbitone and orphenadrine should not be prescribed routinely in patients receiving major tranquillisers. The need for the addition of orphenadrine should be assessed in each individual case.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D009966	Orphenadrine	A muscarinic antagonist used to treat drug-induced parkinsonism and to relieve pain from muscle spasm.	Methyldiphenylhydramine,Disipal,Lysantin,Mefenamine,Mephenamine,Norflex,Norflex Orphenadrine Citrate,Orphenadrine Citrate,Orphenadrine Hydrochloride,Sodium Mefenamine,Citrate, Norflex Orphenadrine,Citrate, Orphenadrine,Hydrochloride, Orphenadrine,Mefenamine, Sodium,Orphenadrine Citrate, Norflex
D010634	Phenobarbital	A barbituric acid derivative that acts as a nonselective central nervous system depressant. It potentiates GAMMA-AMINOBUTYRIC ACID action on GABA-A RECEPTORS, and modulates chloride currents through receptor channels. It also inhibits glutamate induced depolarizations.	Phenemal,Phenobarbitone,Phenylbarbital,Gardenal,Hysteps,Luminal,Phenobarbital Sodium,Phenobarbital, Monosodium Salt,Phenylethylbarbituric Acid,Acid, Phenylethylbarbituric,Monosodium Salt Phenobarbital,Sodium, Phenobarbital
D011618	Psychotic Disorders	Disorders in which there is a loss of ego boundaries or a gross impairment in reality testing with delusions or prominent hallucinations. (From DSM-IV, 1994)	Psychoses,Psychosis, Brief Reactive,Schizoaffective Disorder,Schizophreniform Disorders,Psychosis,Brief Reactive Psychoses,Brief Reactive Psychosis,Disorder, Psychotic,Disorder, Schizoaffective,Disorder, Schizophreniform,Disorders, Psychotic,Disorders, Schizoaffective,Disorders, Schizophreniform,Psychoses, Brief Reactive,Psychotic Disorder,Reactive Psychoses, Brief,Reactive Psychosis, Brief,Schizoaffective Disorders,Schizophreniform Disorder
D002746	Chlorpromazine	The prototypical phenothiazine antipsychotic drug. Like the other drugs in this class chlorpromazine's antipsychotic actions are thought to be due to long-term adaptation by the brain to blocking DOPAMINE RECEPTORS. Chlorpromazine has several other actions and therapeutic uses, including as an antiemetic and in the treatment of intractable hiccup.	Aminazine,Chlorazine,Chlordelazine,Chlorpromazine Hydrochloride,Contomin,Fenactil,Largactil,Propaphenin,Thorazine,Hydrochloride, Chlorpromazine
D002986	Clinical Trials as Topic	Works about pre-planned studies of the safety, efficacy, or optimum dosage schedule (if appropriate) of one or more diagnostic, therapeutic, or prophylactic drugs, devices, or techniques selected according to predetermined criteria of eligibility and observed for predefined evidence of favorable and unfavorable effects. This concept includes clinical trials conducted both in the U.S. and in other countries.	Clinical Trial as Topic
D004347	Drug Interactions	The action of a drug that may affect the activity, metabolism, or toxicity of another drug.	Drug Interaction,Interaction, Drug,Interactions, Drug
D005260	Female		Females
D006207	Half-Life	The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacologic, physiologic, or radiologic activity.	Halflife,Half Life,Half-Lifes,Halflifes
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man