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©2013 UpToDate ® Print Email Systemic analgesics used for labor and vaginal delivery Drug Class Dose Onset Duration Comments Meperidine Opioid 25-50 mg IV 5 min IV 2-3 hr Active metabolite is normeperidine a potent respiratory depressant;neonatal effect most likely if delivery occurs between 1 and 4 hr after administration 50-100 mg IM 40 min IM Morphine Opioid 2-5 mg IV 3-5 min IV 3-4 hr Infrequent use during labor; greater respiratory depression in neonate than meperidine 5-10 mg IM 20-40 min IM Fentanyl Opioid 25-50 mcg IV 1-3 min IV 30-60 min IV Short-acting, potent respiratory depressant; best used by PCA 100 mcg IM 7-10 min IM 1-2 hr IM Nalbuphine Mixed opioid agonist/antagonist 10-20 mg IV 2-3 min IV 3-6 hr Agonist/antagonist; less nausea and vomiting than with meperidine; ceiling of respiratory depression 10-20 mg IM 10-15 min IM Butorphanol Mixed opioid agonist/antagonist 1-2 mg IV or IM 5-10 min IV 3-4 hr Agonist/antagonist; maternal sedation similar to meperidine + phenothiazine; ceiling of respiratory depression; dysphoria 10-15 min IM Pentazocine (Talwin) Mixed opioid agonist/antagonist 20-40 mg IV/IM 2-3 min IV 2-3 hr Agonist/antagonist; ceiling of respiratory depression; dysphoria 5-20 min IM Promethazine (Phenergan) Phenothiazine 25-75 mg IV/IM 10-20 min 3-4 hr Commonly used with opioids to mitigate nausea & vomiting; may produce hypotension Hydroxyzine (Vistaril) Antihistamine 25-50 mg IM 30 min 4 hr Commonly used with opioids to mitigate nausea & vomiting; not used IV (painful on injection) Pentobarbital (Nembutal) Barbiturate 100-200 mg PO/IM 30-60 min 3-6 hr Hypnotic; used only in early or prodromal labor Secobarbital (Seconal) Barbiturate 100 mg PO 30-60 min 3-6 hr Hypnotic; used only in early or prodromal labor Ketamine (Ketalar®) Phencyclidine derivative 10-20 mg IV <1 min 5 min IV dose should not exceed 1 mg/kg per 30 min; psychiatric effects may be prevented with concomitant benzodiazepine; sedation for vaginal delivery; potent amnestic and analgesic 5-10 mg/kg Midazolam (Versed) Benzodiazepine 1-5 mg IV 3-5 min 1-2 hr Sedation and anxiolysis for vaginal delivery; non-irritating when given IV; potent amnestic; rapid onset/offset; used for eclamptic seizures Diazepam (Valium) Benzodiazepine 2-5 mg IV 5 min 1-2 hr IV Sedation and anxiolysis for vaginal delivery; potent amnestic; rapid onset/offset; prolonged half-life; used for eclamptic seizures 10 mg IM 3-4 hr IM