New drug to replace pethidine as birth pain relief


The use of pethidine to relieve pain during birth may be on its way out as a small but growing number of doctors recommend a more powerful opiate that appears safer for babies.

For years, many Australian women have had pethidine injections during labour, but anaesthetists say the drug is not particularly effective at reducing birth pain and can slow the baby's breathing to dangerous levels. Because of its long duration in the body, pethidine can also disrupt a baby's ability to suck and begin breastfeeding.

To overcome these problems, a small but increasing number of doctors worldwide are recommending a more powerful opiate called remifentanil, because it provides stronger pain relief for shorter periods. This means it is processed faster by the baby, reducing the chance of drowsiness and breathing difficulties after birth.

Professor of obstetric anaesthesia at the University of Western Australia Michael Paech said hospitals in countries including Ireland, Scotland, New Zealand, Belgium and Switzerland were embracing the drug because it was more effective than pethidine and morphine for pain relief and was not as invasive as an epidural.

He said most Australian hospitals only used the drug for women who wanted strong pain relief but could not have an epidural because of a spinal abnormality or previous back surgery, for example.

Professor Paech said there were also concerns about the level of medical and nursing attention required to administer remifentanil, because it was generally given intravenously on a continuous basis, as opposed to pethidine and morphine that are given in one intramuscular injection, and because the risks to the mother were greater. He said if a woman overdosed on remifentanil, she could stop breathing or, in the extreme, go into cardiac arrest. However, he said the risk of such a life-threatening incident seemed rare.

''The risk of stopping breathing is exceptionally rare with pethidine and morphine; in fact, it's almost unheard of, whereas with remifentanil it is a higher risk. In Belfast, they have had two significant respiratory events in their first 1500 cases, so that's rare but important, even if it is easy to correct,'' said the anaesthetist, who specialises in obstetrics and works at the King Edward Memorial Hospital in Perth.

Professor Paech said remifentanil could be particularly useful for women in hospitals that did not have an anaesthetist consistently available to perform epidurals. The drug might also appeal to women who did not want an epidural - a spinal nerve and pain block that carries different risks.

He said while epidurals were safe for babies, severe complications for women - such as permanent paralysis from a nerve injury - could affect one in 200,000 patients.

The director of anaesthetics at the Royal Women's Hospital in Melbourne, Dr Andrew Buettner, said he did not know of any Victorian hospitals routinely using remifentanil for women in labour as an alternative to pethidine, but said anaesthetists would monitor safety data published in coming years to see if they should adopt it.