Orphenadrine
Also known as: Mephenamine
The ortho-methyl analogue of antihistamine diphenhydramine, with weak antihistaminic and anticholinergic activities. It has also a mild euphoric action and induces mild exicetment in depressed patients. Chemically, it is identified as N, N-dimethyl-2-[(2-methylphenyl) phenylmethoxy]ethanamine. It is used as a skeletal muscle relaxant to relieve pain and discomfort associated with musculoskeletal injuries. It reduces voluntary muscle spasm by a central effect, and thus has a possible utility in Parkinson's disease. It should be administered orally.<BR>Orphenadrine citrate is a centrally acting (brain stem) compound which in animals selectively blocks facilitatory functions of the reticular formation.
Primary Characteristics
Orphenadrine is also known as Mephenamine, Orphenadrine Citrate, Orphenadrine (HCl).
It belongs to Cholinergic muscarinic antagonist pharmacological group on the basis of mechanism of action and also classified in Muscle Relaxants pharmacological group. It is also classified under Antiparkinson Agents .
Molecular Weight: 305.8 · pKa: 9 · Solubility in Water: sparingly soluble · Solubility in Alcohol: slightly soluble · Non-proprietary name: Orphenadrine.
Pharmacokinetics
Absorption: Orphenadrine has an pre-systemic (first-pass) metabolism accounts for 16% (±14%).
Distribution: Orphenadrine has a plasma protein binding is 95%.
Elimination: it is metabolised via degraded to 8 known metabolites, plasma half-life is 14 hr, renal excretion is 60.8.
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Indications
Orphenadrine is primarily indicated in conditions like Dystonia, Musculoskeletal pain, Parkinsonism, Parkinson's disease, Parkinson's disease; drug-induced extrapyramidal symptoms, Vertigo.
Orphenadrine is also indicated for secondary conditions like Leg cramps.
Contraindications
Orphenadrine is contraindicated in conditions like Glucoma, Peptic ulcer, Prostatic hypertrophy, Pyloric disease.
Dosage
Orphenadrine's dosage details are as follows:
| Dose | Single Dose | Frequency | Route | Instructions |
|---|---|---|---|---|
| Adult Dosage | ||||
| 150 mg | 150 mg | — | Oral | The initial oral |
| 225 mg | 225 mg | — | Oral | For packinsonism Maintenance dose |
| 100 mg | 100 mg | Every 12h | PO | |
| Paediatric Dosage (20kg) | ||||
| 9.166 mg/kg | 9.166 mg/kg | Every 8h | Oral | |
| Neonatal Dosage (3kg) | ||||
| 0 – 0 | — | — | Not recommended in this age group | |
Drug Interactions
Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.
Side Effects
Orphenadrine in overdosage may give rise to further complications which include Hallucinations , Confusion , Hallucinations , Blindness , Chest tightness , Itching, Breathing difficulty.
Orphenadrine produces potentially life-threatening effects which include Anaphylactic shock, Blindness, Preciptate angle closure, Raised Intraoccular pressure. Careful monitoring is needed with proper medical management.
The signs and symptoms that are produced after acute overdosage of Orphenadrine are Tachycardia , Coma, Seizures, Dry mouth, Respiratory depression, Hallucinations , Fever, Dilated pupils, Fainting , Respiratory depression, Shock, Respiratory depression.
Orphenadrine is known to cause more or less tolerable side effects which are usually transient. These include Blurred vision, Confusion, Constipation , Drowsiness, Dry mouth, Hallucination , Headache.
Warnings / Precautions
Interference in Pathology
Orphenadrine may interfere in the diagnosis of Increased Level of Protein Bound Thyroxine .
Available Brands
Storage Conditions
Drug Classification
- 1.20 — Muscle relaxants and cholinesterase inhibitors
Manufacturers
Manufacturers of Orphenadrine in Pakistan: