ORPHENADRINE CITRATE

ORPHENADRINE CITRATE
(or-fen'a-dreen)
Norflex
Classifications: skeletal muscle relaxant, central acting;
Therapeutic: skeletal muscle relaxant, central acting

Prototype: Cyclobenzaprine
Pregnancy Category: C

Availability

100 mg sustained release tablets; 30 mg/mL injection

Action

Tertiary amine anticholinergic agent and central-acting skeletal muscle relaxant. Relaxes tense skeletal muscles indirectly, possibly by analgesic action or by atropinelike central action.

Therapeutic Effect

Relieves skeletal muscle spasm.

Uses

To relieve muscle spasm discomfort associated with acute musculoskeletal conditions.

Contraindications

Narrow-angle glaucoma; pyloric or duodenal obstruction, stenosing peptic ulcers; prostatic hypertrophy or bladder neck obstruction; myasthenia gravis; cardiospasm (megaloesophagus); tachycardia; pregnancy (category C). Safe use in the pediatric age group is not established.

Cautious Use

History of cardiac disease, arrhythmias, coronary insufficiency; renal disease; renal impairment; lactation.

Route & Dosage

Muscle Spasm
Adult: PO 100 mg b.i.d. IM/IV 60 mg, may repeat in 12 h if needed

Administration

Oral
  • Ensure that sustained release form is not chewed or crushed. It must be swallowed whole.
Intravenous

PREPARE: Direct: Give undiluted. Protect from light.  

ADMINISTER: Direct: Give at a rate of 60 mg (2 mL) over 5 min with patient in supine position. Keep supine for 5–10 min post-injection.  

Adverse Effects (≥1%)

CNS: Drowsiness, weakness, headache, dizziness; mild CNS stimulation (high doses: restlessness, anxiety, tremors, confusion, hallucinations, agitation, tachycardia, palpitation, syncope). Special Senses: Increased ocular tension, dilated pupils, blurred vision. GI: Dry mouth, nausea, vomiting, abdominal cramps, constipation. Urogenital: Urinary hesitancy or retention. Body as a Whole: Hypersensitivity [pruritus, urticaria, rash, anaphylactic reaction (rare)].

Interactions

Drug: Propoxyphene may cause increased confusion, anxiety, and tremors; may worsen schizophrenic symptoms, or increase risk of tardive dyskinesia with haloperidol; additive CNS depressant with anxiolytics, sedatives, hypnotics, butorphanol, nalbuphine, opiate agonists, pentazocine, tramadol. Herbal: Valerian, kava potentiate sedation.

Pharmacokinetics

Absorption: Readily from GI tract. Peak: 2 h. Duration: 4–6 h. Distribution: Rapidly distributed in tissues; crosses placenta. Metabolism: In liver. Elimination: In urine. Half-Life: 14 h.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Periodic blood, urine, and liver function studies with prolonged therapy.
  • Report complaints of mouth dryness, urinary hesitancy or retention, headache, tremors, GI problems, palpitation, or rapid pulse to physician. Dosage reduction or drug withdrawal is indicated.
  • Monitor elimination patterns. Older adults are particularly sensitive to anticholinergic effects (urinary hesitancy, constipation); closely observe.
  • Monitor therapeutic drug effect. In the patient with parkinsonism, orphenadrine reduces muscular rigidity but has little effect on tremors. Some reduction in excessive salivation and perspiration may occur, and patient may appear mildly euphoric.

Patient & Family Education

  • Relieve mouth dryness by frequent rinsing with clear tepid water, increasing noncaloric fluid intake, sugarless gum, or lemon drops. If these measures fail, a saliva substitute may help.
  • Do not drive or engage in potentially hazardous activities until response to drug is known.
  • Avoid concomitant use of alcohol and other CNS depressants; these may potentiate depressant effects.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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