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Propoxyphene / Acetaminophen

Pronunciation: pro-POX-ee-feen/ass-cet-ah-MEE-noe-fen
Class: Opioid analgesic combination Propoxyphene Hydrochloride/Acetaminophen

Trade Names

Propoxyphene hydrochloride/Acetaminophen
- Tablets 65 mg propoxyphene hydrochloride/650 mg acetaminophen

Propoxyphene Napsylate/Acetaminophen

Darvocet-N 50
- Tablets 50 mg propoxyphene napsylate/325 mg acetaminophen

Darvocet A500
- Tablets 100 mg propoxyphene napsylate/500 mg acetaminophen

Darvocet-N 100
- Tablets 100 mg propoxyphene napsylate/650 mg acetaminophen


Propoxyphene relieves pain by stimulating opiate receptors in CNS; causes respiratory depression; peripheral vasodilation, inhibition of intestinal peristalsis, sphincter of hepatopancreatic ampulla spasm, stimulation of receptors that cause vomiting, increased bladder tone. Acetaminophen inhibits synthesis of prostaglandins; does not have significant antiinflammatory effects or antiplatelet effects; produces antipyresis by direct action on the hypothalamic heat-regulating center.

Indications and Usage

Relief of mild to moderate pain; as analgesic-antipyretic in presence of aspirin allergy, hemostatic disturbances, bleeding diatheses, upper GI disease, and gouty arthritis.


Standard considerations.

Dosage and Administration

Propoxyphene Napsylate

PO 100 mg (with 500 or 650 mg acetaminophen) every 4 h as needed; max, 600 mg/day.

Propoxyphene hydrochloride

PO 65 mg (with 650 mg acetaminophen) every 4 h; max, 390 mg/day.


The rate of propoxyphene metabolism may be reduced; consider increasing dosing interval.

General Advice

  • Administer without regard to meals. Administer with food if GI upset occurs.
  • 65 mg of hydrochloride form is equivalent to 100 mg of napsylate form in delivering same amount of propoxyphene.


Store at controlled room temperature (68° to 77°F).

Drug Interactions


Increased carbamazepine serum levels; increased risk of acetaminophen hepatotoxicity.


Decreased propoxyphene absorption.

Cigarette smoking

Decreased propoxyphene effect because of liver enzyme induction.

CNS depressants (alcohol, antidepressants, barbiturates, muscle relaxants, sedatives, tranquilizers)

Increased CNS and respiratory depression.


Increased risk of acetaminophen hepatotoxicity.


Increased risk of acetaminophen hepatotoxicity.


Acetaminophen may potentiate the hypoprothrombinemic effect.

Laboratory Test Interactions

Increased amylase and lipase for up to 24 h after administration.

Adverse Reactions




Lightheadedness; weakness; fatigue; sedation; dizziness; disorientation; incoordination; paradoxical excitement; euphoria; dysphoria; insomnia; headache; hallucinations.


Abnormal LFTs; reversible jaundice (including cholestatic jaundice).


Nausea; vomiting; constipation; anorexia; abdominal pain; biliary spasm.


Urinary retention or hesitancy.


Dyspnea; depression of cough reflex.

Special Senses

Minor visual disturbances.


Tolerance; psychological and physical dependence with long-term use; histamine release; skin rashes.



Do not prescribe propoxyphene for patients who are suicidal or addiction-prone. Prescribe with caution for patients taking tranquilizers or antidepressant drugs and patients who use alcohol in excess.


Category C ( Category D if used for prolonged periods).


Excreted in breast milk.


Safety and efficacy not established.

Renal Function

Use drug with caution; reduce total daily dosage; advise chronic alcoholics to limit acetaminophen intake to less than 2 g/day.

Hepatic Function

Use drug with caution; reduce total daily dosage; advise chronic alcoholics to limit acetaminophen intake to less than 2 g/day.

Special Risk Patients

Use with caution in patients with myxedema, acute alcoholism, acute abdominal conditions, ulcerative colitis, decreased respiratory reserve, head injury or increased cranial pressure, hypoxia, supraventricular tachycardia, depleted blood volume or circulatory shock.

Drug dependence

Has abuse potential.


Excessive doses, either alone or in combination with other CNS depressants (including alcohol), are major cause of drug-induced death.



CNS depression (stupor to coma), respiratory depression, hypotension, seizures, pulmonary edema, cardiac arrhythmias, respiratory-metabolic acidosis, Cheyne-Stokes respiration, apnea, circulatory collapse, death.

Patient Information

  • Advise patient to review patient information leaflet before using the first time and with each refill.
  • Advise patient to take prescribed dose without regard to meals but to take with food if GI upset occurs.
  • Advise patient using medication as needed to control pain not to wait until pain level is high to medicate because the medication may not be as effective.
  • Advise patient not to change the dose or stop taking unless advised by health care provider.
  • Caution patient not to exceed prescribed dose and to inform health care provider if prescribed dose does not adequately control pain.
  • Instruct patient to avoid alcoholic beverages and other depressants while taking this medication.
  • Advise patient that drug may impair judgment, thinking, or motor skills, or cause drowsiness, and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.
  • Caution patient that taking acetaminophen or other medications containing acetaminophen can be dangerous.

Copyright © 2009 Wolters Kluwer Health.