Drug information of Orphenadrine
A muscarinic antagonist used to treat drug-induced parkinsonism and to relieve pain from muscle spasm.
Mechanism of effect
Orphenadrine binds and inhibits both histamine H1 receptors and NMDA receptors. It restores the motor disturbances induced by neuroleptics, in particular the hyperkinesia. The dopamine deficiency in the striatum increases the stimulating effects of the cholinergic system. This stimulation is counteracted by the anticholinergic effect of orphenadrine. It may have a relaxing effect on skeletal muscle spasms and it has a mood elevating effect.
Orphenadrine is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute painful musculoskeletal conditions. Orphenadrine is an anticholinergic with a predominantly central effect and only a weak peripheral effect. In addition, it has mild antihistaminic and local anaesthetic properties.
Parkinson's syndrome is the consequence of a disturbed balance between cholinergic and dopaminergic neurotransmission in the basal ganglia caused by a decrease in dopamine. Orphenadrine restores the physiological equilibrium and has a favourable effect on the rigidity and tremor of Parkinson's disease and Parkinsonian syndromes. The effect is somewhat less on bradykinesia.
Half-life elimination: 14-16 hr
Onset: 2-4 hr (peak)
Duration: 4-6 hr
Protein binding: 20%
Metabolites: Not fully determined (>8 metabolites)
Excretion: urine (principally)
Muscle Spasm & Pain
100 mg PO q12hr OR
60 mg IV/IM q12hr (switch to PO as soon as possible)
Safety and efficacy not established
Drug contraindicationsulcerative colitis , Benign Prostatic Hyperplasia , Myasthenia gravis , Hypersensitivity
Side effectsHeadache , dry mouth , Blurred vision , asthenia , palpitations , Tremor , urinary retention , Anaphylactic reaction , itching , aplastic anemia, , difficulty urinating , gastrointestinal disturbances , Restlessness , lightheadedness , Rash , Syncope , vertigo , tachycardia
InteractionsAcetylcholine , Pregabalin , Doxepin , Methocarbamol , Hydroxyzine , Chlorpheniramine , potassium citrate , Butalbital and Acetaminophen , pilocarpine oral , Clonidine , Sodium Oxybate , Sufentanil , Hydrocodone , Huperzine A , Acetaminophen and benzhydrocodone , Ramelteon , Secobarbital , Tolcapone , Clorazepate , Quazepam , Cariprazine , Oxymorphone , Opium , glycopyrrolate topical , ethotoin
Diarrhea, partial obstructive uropathy, open-angle glaucoma, cardiovascular disease, hepatic/renal impairment, cardiac conduction disorder, thyrotoxicosis, history of drug abuse or acute alcoholism
May cause drowsiness/dizziness
May take with food to avoid stomach upset
Injectable form contains sulfites, & precipitates anaphylactic-type reactions in sensitive or asthmatic individuals
Points of recommendation
Follow all directions on your prescription label. Do not take orphenadrine in larger or smaller amounts or for longer than recommended.
Orphenadrine may be habit-forming. Never share orphenadrine with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it.
Orphenadrine is usually taken 2 times per day, once in the morning and once in the evening. Follow your doctor's dosing instructions.
Do not crush, chew, or break an extended-release tablet. Swallow it whole.
Orphenadrine is only part of a complete program of treatment that may also include rest, physical therapy, or other pain relief measures.
Store orphenadrine at room temperature away from moisture, heat, and light. Keep the bottle tightly closed when not in use.
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.