Orphenadrine (sold under the brand names Wilgesic, Norflex, Mephenamin, Disipal, Banflex, Flexon, Biorphen, Brocasipal, and others) is an anticholinergic drug of the ethanolamine antihistamine class with prominent CNS and peripheral actions used to treat painful muscle spasm and other symptoms and conditions as well as some aspects of Parkinson`s Disease. It is closely related to diphenhydramine and therefore related to other drugs used for Parkinson`s like benztropine and trihexyphenidyl and is also structurally related to nefopam, a centrally-acting yet non-opioid analgesic. The combination of anticholinergic effects and CNS penetration make orphenadrine useful for pain of all aetiologies including pain from radiculopathy, muscle pain, headaches, and many others. Some patients report that it feels like orphenadrine and similar drugs help both NSAIDs and opioids find the pain. Orphenadrine has approximately 58 per cent of the anticholinergic potency of atropine at equivalent doses.

Orphenadrine is most often used against pain and muscle spasm of various aetiologies including lumbago, sciatica, and injury. It is quite useful against allergic symptoms and other histimine-related effects, such as those from hayfever, other allergies, and histamine release from many opioid analgesics. Orphenadrine is in many cases helpful against migraine and cluster headaches and is also used for treating some aspects of Parkinson`s Disease including side effects caused by the main therapy in place. Where available for prescription compounding, orphenadrine can also be prepared for topical administration and works slightly better than diphenhydramine for this purpose.

The orphenadrine salt used for Parkinsonism is the hydrochloride, whereas the muscle relaxant tablet are the citrate, and manufacturers` descriptions of orphenadrine indicate that the salts are not interchangeable; one reason may be that the citrate can be irritating when injected.

Euphoria is an effect reported by many patients and orphenadrine has been investigated for use against depression, as first reported in June 1958 in the American Journal of Psychiatry.

Like many first-generation antihistamines and chemically-similar anticholinergics, orphenadrine can also cause excitement and insomnia, particularly in children and the elderly.

Orphenadrine also works on smooth muscle in a manner identical to that of dicyclomine (Bentyl) and will impact Irritable Bowel Syndrome in a similar fashion.

Uses
Orphenadrine is used to treat muscle injuries, skeletal muscle tension and rigidity secondary to afflictions such prolapsed discs and degenerative soft tissue disease especially in the lower back, neck, and joints. and other causes of muscle spasms, to potentiate the action of opioid analgesics against moderate to severe neuropathic pain, and it is also used to treat Parkinson`s disease.

Orphenadrine is also a component of various preparations for use against headaches of various types especially tension and histamine headaches. It is also helpful in many cases of fibromyalgia.

The effect on neuropathic pain, which is also in many cases generated by cyclobenzaprine (Flexeril), atropine, scopolamine, hyoscyamine, trazodone, many first-generation antihistamines, and chemically related drugs like dicyclomine, a.k.a. dicycloverine, (Bentyl), trihexyphenidyl (Artane), first-generation tricyclic antidepressants such as amitriptyline, and other similar drugs, are said by many patients to seem to help the painkillers find the pain. A direct analgesic effect of orphenadrine comes from relaxing painful muscle spasms as well as central antimuscarinic (atropine-like anticholinergic, see below) action and possibly its local anaesthetic effects.

The adjuvant analgesic effect of orphenadrine is neither antagonised nor directly duplicated by some other drugs used for this purpose, such as baclofen (Lioresal), clonidine (Catapres) and others, or gabapentin (Neurontin) so the effects are largely additive if used in combination (same goes for side effects, however), and such medication protocols need close monitoring by a physician especially when other centrally-acting drugs are being used to treat the pain. Cyclobenzaprine, tricyclic anti-depressants, and antihistamines do, however, have additive side effects but little improvement in the clinically desired effects in that they duplicate and compete with each other in this respect.

Orphenadrine can be used in protocols for treating chronic and/or recurring pain as an alternative to gabapentin (Neurontin) as an adjuvant analgesic for management of chronic pain with a neuropathic component amongst those who cannot tolerate the side effects of gabapentin; this is also the case for patients in whom duloxetine (Cymbalta) is contraindicated. Orphenadrine has fewer side effects than many first-generation anti-depressants, cyclobenzaprine, trazadone, clonidine, and other drugs used in chronic pain states.