Version July 2025
| Drug | Class | Dose | Onset | Duration | Comments |
| Fentanyl | Opioid | 25 to 50 mcg IV | 1 to 3 minutes IV | 30 to 60 minutes IV | Short-acting, potent respiratory depressant; best used by PCA. |
| PCA: Patient bolus 10 to 25 mcg IV Lockout 5 to 12 minutes | 1 to 3 minutes | 30 to 60 minutes | |||
| Remifentanil | Opioid | PCA: | 30 to 60 seconds | 3 to 4 minutes | PCA only, start with low dose and titrate to effect; ultrashort acting, potent respiratory depressant. Oxygenation and respiratory rate should be continuously monitored and 1:1 nursing should be strongly considered. |
| Meperidine (Demerol) | Opioid | 25 to 50 mg IV | 5 minutes IV | 2 to 3 hours | Active metabolite is normeperidine, a potent respiratory depressant; neonatal effect most likely if delivery occurs between 1 and 4 hours after administration. |
| 50 to 100 mg IM | 10 to 15 minutes IM | ||||
| Morphine | Opioid | 2 to 5 mg IV | 3 to 5 minutes IV | 2 to 4 hours | Infrequently used during labor; greater neonatal respiratory depression than meperidine. |
| 5 to 10 mg IM | 10 to 20 minutes IM | ||||
| Nalbuphine | Mixed opioid agonist/antagonist | 10 mg IV | 2 to 3 minutes IV | 3 to 6 hours | Less nausea and vomiting than with meperidine; ceiling of respiratory depression. |
| 10 mg IM | 10 to 15 minutes IM | ||||
| Butorphanol (Stadol) | Mixed opioid agonist/antagonist | 1 to 2 mg IV or IM | 5 to 10 minutes IV | 4 to 6 hours | Maternal sedation similar to meperidine and phenothiazine; ceiling of respiratory depression; dysphoria. |
| 30 to 60 minutes IM | |||||
| Pentazocine (Talwin) | Mixed opioid agonist/antagonist | 30 to 60 mg IV/IM | 2 to 3 minutes IV | 2 to 3 hours | Ceiling of respiratory depression; dysphoria. |
| 10 to 20 minutes IM | |||||
| Promethazine (Phenergan) | Phenothiazine | 25 mg IM (preferred) or IV | 10 to 20 minutes | 3 to 4 hours | May be used with opioids to mitigate nausea and vomiting; may produce hypotension. IV administration may cause extravasation injury; administer slowly. |
| Hydroxyzine (Vistaril) | Antihistamine | 25 to 50 mg IM | 30 minutes | 4 hours | May be used with opioids to mitigate nausea and vomiting; not used IV (painful on injection). |
| Ketamine (Ketalar) | Phencyclidine derivative | 10 to 20 mg IV | <1 minute | 5 minutes | IV dose should not exceed 1 mg/kg per 30 minutes; psychotomimetic effects may be prevented with concomitant benzodiazepine; sedation for vaginal delivery; potent amnestic and analgesic. |
| Midazolam (Versed) | Benzodiazepine | 1 to 5 mg IV | 3 to 5 minutes | 1 to 2 hours | Sedation and anxiolysis for vaginal delivery; non-irritating when given IV; potent amnestic; rapid onset/offset; used for eclamptic seizures. |
| Diazepam (Valium) | Benzodiazepine | 2 to 5 mg IV | 5 minutes | 1 to 2 hours IV | Sedation and anxiolysis for vaginal delivery; potent amnestic; rapid onset/offset; prolonged half-life; used for eclamptic seizures. |
| Nitrous oxide | Anesthetic gas | 50% inhaled | Up to 50 seconds | Varies, very rapid offset | In United States, must administer with blender and scavenging; lag time for effect; inhalation should begin approximately 30 seconds before contraction, and end as contraction recedes. |
