Pethidine (Meperidine)

Brand Names: Pethidine

Drug Class: Opioid Analgesic

Overview

Pethidine (Meperidine) is a synthetic opioid analgesic with moderate potency, primarily used for moderate to severe pain management. It acts on the central nervous system to relieve pain but has a shorter duration of action compared to morphine. Due to its metabolite normeperidine, which can cause neurotoxicity (seizures) with repeated use or in renal impairment, its use is now limited and often reserved for specific situations like acute pain or anesthesia adjunct.

Mechanism of Action

Pethidine is a mu-opioid receptor agonist in the central nervous system, inhibiting pain transmission by mimicking endogenous opioids. It also has anticholinergic effects and local anesthetic properties. Its active metabolite, normeperidine, contributes to analgesic effects but can accumulate and cause excitatory neurotoxicity.

Indications

  • Moderate to severe acute pain (e.g., postoperative pain)
  • Obstetric analgesia during labor
  • Preoperative medication
  • Adjunct to anesthesia

Dosage

Adults: 50-150 mg IM, SC, or IV every 3-4 hours as needed for pain. Maximum daily dose typically 600 mg, but lower in renal impairment. Pediatric: 1-1.8 mg/kg IM or SC every 3-4 hours, not to exceed adult doses. Use with caution and reduced doses in elderly or renally impaired patients.

Contraindications

  • Hypersensitivity to pethidine or other opioids
  • Concurrent use with MAO inhibitors or within 14 days of discontinuation (risk of serotonin syndrome)
  • Severe respiratory depression
  • Acute or severe bronchial asthma
  • Paralytic ileus
  • Increased intracranial pressure

Side Effects

  • Common: Nausea, vomiting, dizziness, sedation, sweating
  • Serious: Respiratory depression, hypotension, seizures (from normeperidine), serotonin syndrome (with MAOIs), anaphylaxis
  • Other: Constipation, urinary retention, dry mouth, euphoria, dependency

Interactions

  • MAO inhibitors: Contraindicated due to risk of serotonin syndrome and hyperpyrexia
  • Other CNS depressants (e.g., alcohol, benzodiazepines): Enhanced sedation and respiratory depression
  • SSRIs/SNRIs: Increased risk of serotonin syndrome
  • Anticholinergic drugs: Enhanced anticholinergic effects
  • Rifampin: Decreased pethidine efficacy