orphenadrine (Rx)

Frequency Not Defined

Dry mouth

Urinary retention

Blurred vision, mydriasis

Drowsiness

Headache

Weakness

Increased IOP

Palpitation

Tachycardia

GI disturbances

CNS stimulation (restlessness, agitation, insomnia, mental confusion)

Lightheadedness

Dizziness

Syncope

Pruritus

Urticarial rash

Tremor

Anaphylactic reactions

Aplastic anemia

Contraindications

Hypersensitivity

Narrow-angle glaucoma

Pyloric/duodenal obstruction, BPH, stenosing peptic ulcers, cardiospasm (mega-esophagus), myasthenia gravis, obstructive uropathy, paralytic ileus, ulcerative colitis, toxic megacolon, achalasia

Cautions

Use caution in patients with diarrhea, partial obstructive uropathy, open-angle glaucoma, cardiovascular disease, hepatic/renal impairment, thyrotoxicosis, history of drug abuse or acute alcoholism

Some patients may experience transient episodes of light-headedness, dizziness or syncope; drug may impair ability of patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle; ambulatory patients should be cautioned

May take with food to avoid stomach upset

Use with caution in patients with tachycardia, cardiac decompensation, coronary insufficiency, cardiac arrhythmias

Injectable form contains sulfites, & precipitates anaphylactic-type reactions in sensitive or asthmatic individuals

Safety of continuous long-term therapy not established; if orphenadrine is prescribed for prolonged use, periodic monitoring of blood, urine and liver function values is recommended

Drug interaction overview

• Confusion, anxiety and tremors have been reported in patients receiving propoxyphene and orphenadrine concomitantly; as symptoms may be simply due to an additive effect, reduction of dosage and/or discontinuation of one or both agents is recommended in such cases

Pregnancy Category: C

Lactation: no data

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

May work through central atropine-like effect; anticholinergic activity in brain stem; has euphorigenic and analgesic properties

Pharmacokinetics

Half-life elimination: 14-16 hr

Onset: 2-4 hr (peak)

Duration: 4-6 hr

Metabolism: Liver

Protein binding: 20%

Metabolites: Not fully determined (>8 metabolites)

Excretion: urine (principally)

IV/IM Administration

Administer IM or IV injection

IV may be given undiluted or diluted in SWI

Give slow IV ~5 min with pt in supine position

Patient should remain in this position for 5-10 min post-injection

To minimize adverse reactions after parenteral administration of the drug, patient should be assisted from recumbent position

Storage

Store at <40°C, preferably between 15-30°C

Protect from freezing

Protect from light; store in tight, light-resistant containers