Drug Guide
Acetaminophen; Propoxyphene Napsylate
Classification
Therapeutic: Analgesic, Narcotic (opioid) and Non-opioid Analgesic
Pharmacological: opioid agonist (propoxyphene), NSAID-like (acetaminophen)
FDA Approved Indications
- Relief of mild to moderate pain
Mechanism of Action
Propoxyphene is an opioid agonist that acts on the central nervous system to relieve pain. Acetaminophen inhibits prostaglandin synthesis in the central nervous system, providing analgesic and antipyretic effects.
Dosage and Administration
Adult: Typically 100 mg propoxyphene with 650 mg acetaminophen every 4 hours as needed, not to exceed 600 mg of propoxyphene in 24 hours.
Pediatric: Not recommended for children under 12 years due to safety concerns.
Geriatric: Careful dose adjustment due to increased risk of adverse effects, generally start at lower doses.
Renal Impairment: Use with caution; adjust dose if necessary.
Hepatic Impairment: Use with caution; dose reduction may be necessary due to hepatic metabolism.
Pharmacokinetics
Absorption: Well absorbed from gastrointestinal tract.
Distribution: Widely distributed in body tissues, crosses the blood-brain barrier.
Metabolism: Hepatic; mainly via conjugation with glucuronic acid and sulfate.
Excretion: Renal; mainly as conjugates.
Half Life: Propoxyphene about 6-12 hours; acetaminophen about 2-3 hours.
Contraindications
- Known hypersensitivity to acetaminophen or propoxyphene.
- Use with monoamine oxidase inhibitors (MAOIs).
Precautions
- History of substance abuse, respiratory depression, use in pregnant or breastfeeding women, caution in hepatic impairment.
Adverse Reactions - Common
- Drowsiness (Common)
- Dizziness (Common)
- Nausea (Common)
Adverse Reactions - Serious
- Respiratory depression (Rare)
- Hepatotoxicity (due to acetaminophen overdose) (Rare)
- Dependency or abuse potential (Rare)
Drug-Drug Interactions
- CNS depressants, other opioids, sedatives, alcohol, CYP3A4 inhibitors
Drug-Food Interactions
- Alcohol (risk of hepatotoxicity)
Drug-Herb Interactions
- St. John's Wort (may increase metabolism of propoxyphene)
Nursing Implications
Assessment: Assess pain characteristics, assess hepatic function, monitor for signs of respiratory depression.
Diagnoses:
- Acute pain
- Risk for respiratory depression
Implementation: Administer with food or milk to reduce gastrointestinal irritation. Monitor for adverse effects.
Evaluation: Assess pain relief efficacy and monitor for side effects.
Patient/Family Teaching
- Do not exceed prescribed dose.
- Avoid alcohol and CNS depressants.
- Report any signs of allergic reactions or adverse effects.
- Store in a safe place out of reach of children.
Special Considerations
Black Box Warnings:
- Potential for respiratory depression, abuse, and dependence.
- High risk of overdose leading to hepatotoxicity from acetaminophen.
Genetic Factors: None specified.
Lab Test Interference: May interfere with certain liver function tests.
Overdose Management
Signs/Symptoms: CNS depression, respiratory depression, nausea, vomiting, sweating, dullness, coma, hepatotoxicity (overdose of acetaminophen).
Treatment: Administer opioid antagonists like naloxone for respiratory depression, provide supportive care, and administer acetylcysteine within 8-10 hours of overdose to prevent hepatotoxicity.
Storage and Handling
Storage: Store at room temperature, away from moisture and heat.
Stability: Stable under recommended conditions.