Meperidine (demerol, pethidine) is one of the most commonly prescribed opioids for labor pain relief worldwide because it is readily available and inexpensive. However its use has fallen into disfavor in the United States because it offers no advantage over other opioids as an analgesic and has potential dangerous side effects:
- Seizures. Meperidine is metabolized to normeperidine in the liver and this metabolite is excreted very slowly in the urine (half life 17 hours); even slower if concomitant renal failure. When normeperidine accumulates it can cause delirium, hallucinations, psychosis and generalized seizures.
- Serotonin syndrome. When used along with other serotonin modulators (ie MAO inhibitors, selective serotonin) serotonin syndrome may be induced.
- Prolonged neonatal effects. Meperidine reaches maximal concentration in the fetus between two and three hours after maternal dosing. If the neonate is not delivered before this time, the medication will have crossed the placenta and may affect neonatal respiratory and feeding drive for several hours to days given its prolonged half life (2.5 days in the neonate ).
Marino, P. MD. The ICU Book. 2nd ed.
Grant, G. MD. "Pharmacologic management of pain during labor and delivery" Up to Date. 2 June 2008.
