TABLE 25-3. Some Parenteral Analgesic Agents for Labor Pain
Meperidine 25-50 mg (IV) Q 1-2 hr 5 min (IV) �.1A8-20 hr 50-100 mg (1M) Q 2-4 hr 30-45 min (1M) �60 hr Fentanyl 50-100 tg (IV) Q 1 hr 1 min �5 hr Morphine 2--5 mg (IV) Q 4 hr 5 min (IV) �.7 hr
IV = intravenously, 1M = intramuscularly; Q = every.
According to Bricker and Lavender (2002), meperidine is the most common opioid used worldwide for pain relief during labor. In one randomized study at Parkland Hospital, patientcontrolled intravenous analgesia with meperidine was found to be an inexpensive and reasonably efective method for labor analgesia (Sharma, 1997). Women randomized to self-administered analgesia were given a 50-mg meperidine plus 25-mg promethazine dose intravenously as an initial bolus. hereafter, an infusion pump was set to deliver 15 mg of meperidine every 10 minutes as needed until delivery. Neonatal sedation, as measured by the need for naloxone treatment in the delivery room, was identiied in 3 percent of newborns. Both meperidine and its metabolite, normeperidine, are lipophilic and readily cross the placenta. Analgesia with meperidine was associated with lower Apgar scores in comparison to epidural analgesia (Sharma, 2004). Normeperidine is a strong respiratory depressant that has a significantly longer half-life than meperidine and is likely responsible for the fetal side efects of meperidine.
his synthetic opioid receptor agonist-antagonist analgesic, given in 1-to 2-mg intravenous doses, compares favorably with 40 to 60 mg of meperidine. Its major side efects are somnolence, dizziness, and dysphoria. Neonatal respiratory depression is reported to be less than with meperidine. Importantly, the two drugs are not given contiguously because butorphanol antagonizes the narcotic efects of meperidine. Butorphanol has been associated with transient sinusoidal fetal heart rate patterns (Hatjis, 1986).
This is another mixed opioid receptor agonist-antagonist analgesic. It can be given intramuscularly, intravenously, or subcutaneously. he usual dose is 10 to 20 mg, administered every 4 to 6 hours irrespective of the route of administration. Small doses of nalbuphine may also be used to treat pruritus associated with neuraxial opioids.
This short-acting and potent synthetic opioid may be given in doses of 50 to 1 00 �g intravenously every hour. Its main disadvantage is its short duration of action, which requires frequent dosing or use of a patient-controlled intravenous infusion pump.
This is a synthetic opioid with an extremely rapid onset of action. It is hydrolyzed rapidly, resulting in a half-life of 3.5 minutes (Ohashi, 2016). Although it readily crosses the placenta, it is quickly metabolized or redistributed within the fetus (Kan, 1998). Various dosing regimens have been studied, and single boluses appear to mirror the periodic uterine contraction pattern. Infusions, on the other hand, have been reported to cause maternal apnea (Waring, 2007). Due to the aforementioned risks, only trained personnel should administer it, and only under strictly controlled circumstances.
Efficacy and Safety of Parenteral Agents