Pharmacological - parenteral

Nowadays the principal remaining narcotic used is pethidine, which midwives may give without a doctor's prescription. Pethidine is a central nervous system depressant. This drug has an onset of action of about 15 minutes and a duration of action of 2-4 hours. A standard dose would be 50-100mg IM repeated 1-3hrs later if necessary. Max dose 400mg in 24hrs.

The advantages are: - cheapness - widely available - midwives like it

The disadvantages are: - mothers don't like it because of misinformation - unsafe for mother - gastric stasis, nausea, dysphoria, reduced cooperation from mother - unsafe for baby - fetal depression - limited effectiveness - often given with promethazine, thus increasing the dangers and further reducing analgesic efficacy

Narcotic antagonists are used in order to prevent respiratory depression of infants. This is done via intravenous administration to the mother at least 20 minutes before delivery, or administration to the infant (via the umbilical vein or i.m.).

Mild sedatives and tranquillisers have no analgesic effect. However they help to reduce anxiety and apprehension. Also the anti-emetic effect of drugs such as promethazine is useful considering the emetic effects of narcotics.

NICE (1) state:

• intravenous and intramuscular opioids
  • pethidine, diamorphine or other opioids should be available in all birth settings. Women should be informed that these will provide limited pain relief during labour and may have significant side effects for both the woman (drowsiness, nausea and vomiting) and her baby (short-term respiratory depression and drowsiness which may last several days)
  • women should be informed that pethidine, diamorphine or other opioids may interfere with breastfeeding
  • if an intravenous or intramuscular opioid is used, it should be administered with an antiemetic
  • women should not enter water (a birthing pool or bath) within 2 hours of opioid administration or if they feel drowsy

Reference:

1. NICE (September 2007).Intrapartum care.