Formula C18H23NO·HCl
Molar Mass (g·mol−1) 305,84 g
Physical State solid
Melting Point (°C) < 25
Boiling Point (°C) 195
PKS Value 8,91
CAS Number 341-69-5
PUB Number 4601
Drugbank ID DB01173
Solubility sparingly soluble in water


Orphenadrine is a centrally acting muscle relaxant and belongs to the group of H1 antihistamines. It is used to treat painful skeletal muscle tension and Parkinson's disease.

Orphenadrine is available by prescription and is usually given in the form of tablets or liquid preparations for ingestion. In some cases, it is also administered intravenously. It is available either as a monopreparation or in combination with paracetamol or diclofenac.



Orphenadrine is a so-called anticholinergic with an effect on the central nervous system. On the peripheral nervous system, orphenadrine has very little effect. In addition, it shows properties of an antihistamine as well as those of a local anaesthetic.

The mechanism of action is primarily based on a blockade of glutamate receptors. Glutamate is a very important excitatory neurotransmitter in the human brain. When blocked by orphenadrine, muscles become less excited and relaxation occurs.


Orphenadrine is absorbed into the blood mainly through the gastrointestinal tract. Plasma protein binding is 95% and plasma half-life is between 13-20 hours. Degradation of the drug occurs entirely in the cells of the liver.

Drug Interactions

The agents amantadine, quinidine, MAO inhibitors, and some tricyclic antidepressants may potentiate the anticholinergic effect of Orphenadrine. Orphenadrine may potentiate the effects of L-dopa. There is a risk of hypothermia if chlorpromazine is taken concomitantly. The consumption of alcohol should be avoided while taking Orphenadrine.


Toxicological data

Oral, mouse LD50 = 100 mg/kg; oral, rat LD50 = 255 mg/kg


Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter ist Autor zu pharmazeutischen Themen in der Medizin-Redaktion von Medikamio. Er befindet sich im letzten Semester seines Pharmaziestudiums an der Universität Wien und liebt das wissenschaftliche Arbeiten im Bereich der Naturwissenschaften.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer ist seit 2020 freie Autorin bei Medikamio und studierte Pharmazie an der Universität Wien. Sie arbeitet als Apothekerin in Wien und ihre Leidenschaft sind pflanzliche Arzneimittel und deren Wirkung.

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