Orphenadrine
NORFLEX
What it isAntimuscarinic, H1, and NMDA antagonist used for acute musculoskeletal spasm.
Why this oneUnlike purely sedating relaxants, it adds an NMDA-linked analgesic component, though efficacy evidence is weak.
What limits itAnticholinergic burden makes it poor for older adults. Overdose can be lethal through arrhythmia, seizure, and coma.
FDA-approved for
- muscle spasm (~1959)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Adjunct for acute painful musculoskeletal conditions | Adults | 1 tablet BID (one AM, one PM) | 1 tablet BID | 1 tablet BID |
Renal Undefined
Hepatic Undefined
Instructions
- Take one tablet in the morning and one in the evening
Contraindications
- Glaucoma
- Pyloric or duodenal obstruction
- Stenosing peptic ulcers
- Prostatic hypertrophy or bladder-neck obstruction
- Cardiospasm (megaesophagus)
- Myasthenia gravis
Cautions
- Anticholinergic effects (dry mouth, tachycardia, urinary retention, blurred vision), dose-related
- Rare aplastic anemia reported
- Mental confusion may occur in elderly patients
Adverse reactions
- Dry mouth
- Tachycardia/palpitation
- Urinary hesitancy or retention
- Blurred vision/mydriasis
- Nausea/vomiting
- Headache
- Dizziness
- Constipation
- Drowsiness
- Agitation/tremor/hallucinations
- Pruritus
Pregnancy Pregnancy Category C; use only if clearly needed
Lactation Undefined
NO BOXED WARNINGS
Principal riskAnticholinergic burden; lethal in overdose
Cost, est. cash$10–$300/month
Generic entry1982
Classes and tags
Clinical profile
Legacy pregnancy categoryUnknown / historical label unavailable
Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.
Mechanism of action: Orphenadrine ballicule
Open Orphenadrine in the interactive console ↗
Memory aids: mascots and interaction avatars
muscles → muscle relaxant
