Indications: pre-operative analgesia; pre-medication; analgesia in obstetrics; moderate to severe pain.

Cautions: head injuries, severe hepatic or renal impairment, biliary tract disorders, hypothyroidism; patients exhibiting acute alcoholism, raised intracranial pressure, convulsive disorders. not suitable for severe continuing pain;

Contra-indications: avoid in acute respiratory depression, acute alcoholism and where risk of paralytic ileus; avoid injection in pheochromocytoma; severe renal impairment

Side Effects: nausea and vomiting (particularly in initial stages), constipation, and drowsiness; larger doses produce respiratory depression, hypotension, and muscle rigidity; other side effects: include difficulty with micturition, ureteric or biliary spasm, dry mouth, sweating, headache, facial flushing, vertigo, bradycardia, tachycardia, palpitation, postural hypotension, hypothermia, hallucinations, dysphoria, mood changes, dependence, miosis, decreased libido or potency, rashes, urticaria and pruritus; convulsions reported in overdosage.

Dose: pre-medication, by IM injection, 50-100 mg 1 hour before operation;

Child, l-2mg/kg. Adjunct to nitrous oxide-oxygen, by IV injection, 10-25 mg repeated when required.