Chemical formula: C₁₈H₂₃NO Molecular mass: 269.381 g/mol PubChem compound: 4601
Orphenadrine, which is a congener of diphenhydramine without sharing its soporific effect, is an anti-muscarinic agent. It also works has weak antihistaminic and local anaesthetic properties.
Orphenadrine is used as the hydrochloride in the symptomatic treatment of Parkinsonism. It is also used to alleviate the extrapyramidal syndrome induced by drugs such as the phenothiazine derivatives, but is of no value in tardive dyskinesia, which may be exacerbated.
Orphenadrine citrate is the citrate salt of orphenadrine (2-dimethylaminoethyl 2-methylbenzhydryl ether citrate).
The mode of therapeutic action has not been clearly identified, but may be related to its analgesic properties. Orphenadrine citrate does not directly relax tense skeletal muscles in man. Orphenadrine citrate also possesses anti-cholinergic actions.
Orphenadrine is readily absorbed from the gastro-intestinal tract. It is rapidly distributed in tissues and most of a dose is metabolised to at least 8 metabolites and excreted in the urine along with a small proportion of unchanged drug. A half life of 14 hours has been reported.
Orphenadrine is a drug on which extensive clinical experience has been obtained. Relevant information for the prescriber is provided elsewhere in this summary.
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