API

Pethidine

Drug classification

Opioid analgesic (phenylpiperidine opioid).

Dosage form

Injection

API strength per dosage

50MG/ML

Dose

Adults: 25–100 mg IM or slow IV every 4 hours as needed. Children: 0.5–2 mg/kg IM or slow IV every 4 hours as needed. Elderly or renal/hepatic impairment: Use lowest effective dose, reduce frequency, and monitor closely.

Mechanism of action

Binds primarily to μ-opioid receptors (MOR) in the central nervous system, acting as an agonist, inhibiting adenylate cyclase, decreasing cAMP, reducing neuronal excitability, and inhibiting presynaptic release of neurotransmitters, resulting in analgesia and sedation. Also exhibits weak antagonism at NMDA receptors and inhibits neuronal reuptake of serotonin and noradrenaline.

Indications

Moderate to severe pain, preoperative analgesia, obstetric analgesia (including labor pain), perioperative pain management, adjunct to anesthesia.

Side effects

Respiratory depression, hypotension, bradycardia, sedation, nausea, vomiting, constipation, dizziness, confusion, urinary retention, allergic reactions, seizures, dependence, pruritus.

Pregnancy category

Precautions

Respiratory depression, hypotension, head injury, hepatic or renal impairment, elderly or debilitated patients, seizure disorders, concurrent MAOI use, pregnancy and lactation, risk of dependence and abuse, biliary tract disorders, prostatic hypertrophy, acute asthma, avoid abrupt discontinuation, monitor for serotonin syndrome with serotonergic drugs.

Contraindications

Hypersensitivity to pethidine, severe respiratory depression, acute asthma, head injury, raised intracranial pressure, severe hepatic impairment, concurrent monoamine oxidase inhibitor use, prostatic hypertrophy with urinary retention, uncontrolled epilepsy.