Propoxyphene and Acetaminophen

Pronunciation

(proe POKS i feen & a seet a MIN oh fen)

U.S. Brand Names

Darvocet A500™; Darvocet-N® 50; Darvocet-N® 100; Pronap-100®

Synonyms

Propoxyphene Hydrochloride and Acetaminophen; Propoxyphene Napsylate and Acetaminophen

Generic Available

Yes

Canadian Brand Names

Darvocet-N® 50; Darvocet-N® 100

Use

Management of mild to moderate pain

Use - Dental

Management of postoperative pain

Restrictions

C-IV

Pregnancy Risk Factor

Pregnancy Implications

Withdrawal symptoms have been reported in the neonate following propoxyphene use during pregnancy. Teratogenic effects have also been noted in case reports. Opioid analgesics are considered pregnancy risk factor D if used for prolonged periods or in large doses near term.

Lactation

Enters breast milk/compatible

Contraindications

Hypersensitivity to propoxyphene, acetaminophen, or any component of the formulation

Warnings/Precautions

When given in excessive doses, either alone or in combination with other CNS depressants, propoxyphene is a major cause of drug-related deaths; do not exceed recommended dosage; give with caution in patients dependent on opiates, substitution may result in acute opiate withdrawal symptoms. Avoid use in severely-depressed or suicidal patients. Tolerance or drug dependence may result from extended use.

Propoxyphene should be used with caution in patients with renal or hepatic dysfunction or in the elderly; consider dosing adjustment. Acetaminophen should be used with caution in patients with liver disease; consuming 3 alcoholic drinks/day may increase risk of liver damage. Use caution in patients with known G6PD deficiency. Safety and efficacy of this combination have not been established in pediatric patients.

Adverse Reactions

See individual agents.

Drug Interactions

Propoxyphene: Inhibits CYP2C8/9 (weak), 2D6 (weak), 3A4 (weak)

Acetaminophen: Substrate (minor) of CYP1A2, 2A6, 2C8/9, 2D6, 2E1, 3A4; Inhibits CYP3A4 (weak)

Also see individual agents.

Ethanol/Nutrition/Herb Interactions

Based on propoxyphene component:

Ethanol: Avoid or limit ethanol (may increase CNS depression). Watch for sedation.

Food: May decrease rate of absorption, but may slightly increase bioavailability.

Based on acetaminophen component:

Ethanol: Excessive intake of ethanol may increase the risk of acetaminophen-induced hepatotoxicity. Avoid ethanol or limit to <3 drinks/day.

Food: Rate of absorption may be decreased when given with food.

Herb/Nutraceutical: St John's wort may decrease acetaminophen levels.

Stability

Store at controlled room temperature.

Mechanism of Action

Propoxyphene is a weak narcotic analgesic which acts through binding to opiate receptors to inhibit ascending pain pathways

Propoxyphene, as with other narcotic (opiate) analgesics, blocks pain perception in the cerebral cortex by binding to specific receptor molecules (opiate receptors) within the neuronal membranes of synapses. This binding results in a decreased synaptic chemical transmission throughout the CNS thus inhibiting the flow of pain sensations into the higher centers. Mu and kappa are the two subtypes of the opiate receptor which propoxyphene binds to to cause analgesia.

Acetaminophen inhibits the synthesis of prostaglandins in the CNS and peripherally blocks pain impulse generation; produces antipyresis from inhibition of hypothalamic heat-regulating center

Pharmacodynamics/Kinetics

See individual agents.

Dosage

Oral: Adults:

Darvocet A500™, Darvocet-N® 100: 1 tablet every 4 hours as needed; maximum: 600 mg propoxyphene napsylate/day

Darvocet-N® 50: 1-2 tablets every 4 hours as needed; maximum: 600 mg propoxyphene napsylate/day

Note: Dosage of acetaminophen should not exceed 4 g/day (6 tablets of Darvocet-N® 100); possibly less in patients with ethanol

Elderly: Refer to Adults dosing

Dosing adjustment in renal/hepatic impairment: Serum concentrations of propoxyphene may be increased or elimination may be delayed; specific dosing recommendations not available.

Administration

Should be administered with water on an empty stomach.

Dietary Considerations

May be taken with food if gastrointestinal distress occurs.

Patient Education

See individual agents. Pregnancy precaution: Inform prescriber if you are or intend to become pregnant.

Nursing Implications

Monitor pain relief, respiratory and mental status, blood pressure, excessive sedation

Additional Information

Some studies have found no significant difference in pain relief between propoxyphene and aspirin or acetaminophen.

Dental Health: Effects on Dental Treatment

Key adverse event(s) related to dental treatment: Xerostomia (normal salivary flow resumes upon discontinuation).

Dental Health: Vasoconstrictor/Local Anesthetic Precautions

No information available to require special precautions

Dental Comment

Propoxyphene is a narcotic analgesic and shares many properties including addiction liability. The acetaminophen component requires use with caution in patients with alcoholic liver disease.

Mental Health: Effects on Mental Status

Dizziness, drowsiness, insomnia, and paradoxical excitement are common; may cause nervousness, restlessness, confusion; may rarely cause depression or hallucinations

Mental Health: Effects on Psychiatric Treatment

Concurrent use with psychotropics may produce additive sedation as well as increase their serum levels; monitor for altered clinical response or preferably, use a different analgesic

Dosage Forms

Tablet: Propoxyphene hydrochloride 65 mg and acetaminophen 650 mg, propoxyphene napsylate 100 mg, and acetaminophen 650 mg

Darvocet A500™: Propoxyphene napsylate 100 mg and acetaminophen 500 mg [contains lactose]

Darvocet-N® 50: Propoxyphene napsylate 50 mg and acetaminophen 325 mg

Darvocet-N® 100, Pronap-100®: Propoxyphene napsylate 100 mg and acetaminophen 650 mg

References

"American Academy of Pediatrics Committee on Drugs. The Transfer of Drugs and Other Chemicals Into Human Milk," Pediatrics , 2001, 108(3):776-89.

"Drugs for Pain," Med Lett Drugs Ther , 2000, 42(1085):73-8.

Mokhlesi B, Leikin JB, Murray P, et al, "Adult Toxicology in Critical Care: Part II: Specific Poisonings," Chest , 2003, 123(3):897-922.

Rathmell JP, Viscomi CM, and Ashburn MA, "Management of Nonobstetric Pain During Pregnancy and Lactation," Anesth Analg , 1997, 85(5):1074-87.

International Brand Names

Darvocet-N® 50 (CA); Darvocet-N® 100 (CA)

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