skeletal muscle relaxant, antihistaminic agent
Muscle relaxant (skeletal); antihistaminic
ChEBI: A citrate salt which comprises equimolar amounts of orphenadrine and citric acid.
As described in US Patent 2,567,351, o-methylbenzhydryl bromide is added slowly to β-dimethylaminoethanol at refluxing temperature. After the addition has been completed the mixture is refluxed and stirred for an additional 16 hours. The mixture is cooled and the bottom layer consisting of the crude hydrobromide salt of β-dimethylaminoethanol is drawn off. The excess amino alcohol is distilled from the upper layer in vacuo and the residue is reacted with citric acid.
Norflex (3M Pharmaceuticals).
Orphenadrine citrate, N,Ndimethyl-2-(o-methyl-α-phenylbenzyloxy)ethylamine citrate(1:1) (Norflex), introduced in 1957, is closely related todiphenhydramine structurally but has much lower antihistaminicactivity and much higher anticholinergic action.Likewise, it lacks the sedative effects characteristic ofdiphenhydramine. Pharmacological testing indicates that itis not primarily a peripherally acting anticholinergic becauseit has only weak effects on smooth muscle, on the eye,and on secretory glands. It does reduce voluntary musclespasm, however, by a central inhibitory action on cerebralmotor areas, a central effect similar to that of atropine.
Orphenadrine citrate is used for the symptomatic treatment ofParkinson disease. It relieves rigidity better than it doestremor, and in certain cases, it may accentuate the latter. Thedrug combats mental sluggishness, akinesia, adynamia, andlack of mobility, but this effect seems to diminish rather rapidlywith prolonged use. It is best used as an adjunct to theother agents, such as benztropine, procyclidine, cycrimine,and trihexyphenidyl, in the treatment of paralysis agitans.Orphenadrine citrate is also used as an adjunct to rest, physiotherapy,and other measures to relieve pain of local musclespasm (e.g., nocturnal leg cramps).
The drug has a low incidence of the usual side effectsfor this group, namely, dryness of mouth, nausea, and mildexcitation.
