A study of pethidine kinetics and analgesia in women in labour following intravenous, intramuscular and epidural administration.

Abstract

1 Epidural administration of opiates for analgesia has recently generated widespread interest and would theoretically be advantageous as a method for relief of pain in labour. 2 Plasma pethidine concentrations were measured after intravenous, intramuscular and epidural administration of pethidine to women in labour and after epidural administration to non-pregnant female surgical patients. 3 Kinetic parameters were derived from the plasma concentration data in each group of subjects and the relationship between plasma kinetics and analgesia in labour were examined. 4 Absorption of pethidine from the epidural space in pregnant women is rapid and excepting the lower initial values, the average plasma concentration and area under the plasma concentration v time curve did not differ significantly (P < 0.01) from those obtained with intravenous dosage, but were significantly higher (P < 0.01) during the first 2 h after dosage than the results after intramuscular administration. The analgesia provided by the epidural route of administration was greater than with intravenous or intramuscular administration. 5 It is postulated that the analgesic efficacy of epidural pethidine in women in labour is due to a combination of systemic and local effects and that the local effect is attributable to the local anaesthetic properties of pethidine rather than a selective anti-nociceptive action on the spinal cord.

A double blinded randomised placebo‐controlled study of intramuscular pethidine for pain relief in the first stage of labour

“…We chose to give women a standard dose of 100 mg pethidine, the dose used in most obstetrics departments in Hong Kong, which was equivalent to a mean dose of 1.56 mg/kg. This is greater than that used in many other studies 3,5,25 . Despite this, we found that the mean plasma concentration of pethidine 30 minutes after injection was slightly less than the previously reported mean effective analgesic concentration for pethidine 19 .…”

Prescribing intramuscular opioids for labour analgesia in consultant-led maternity units: a survey of UK practice

“…It was noted that the dose regimens and intervals for different opioids were not related to the duration of action of the individual drugs or comparative potencies and this may have an effect on the efficacy of analgesia. 5,6,[15][16][17][18][19] This may reflect, in part, the lack of published data to suggest the most effective opioid and dosing regimen. 5,6 The dose for optimal maternal analgesia may cause excessive neonatal sedation.…”

Early respiratory depression during Caesarean section following epidural meperidine

“…Husemeyer et al 22 showed that the mean plasma meperidine concentration exceeded 600 ng" ml -t ten minutes after injection of 100 mg of meperidine into the lumber epidural space in labouring women. This was higher (P < 0.05) than plasma levels achieved in the non-pregnant woman following an identical dose of epidural meperidine.…”