Drugs & their effects

Drugs and anaesthetics Before accepting any drugs their possible effects should be considered carefully. Questions to ask What to ask if you are offered drugs for easing pain in labour Anaesthetic injections Anaesthetic drugs can be given by injection to relieve pain during labour. Addiction The link between drugs for pain in labour and later drug addiction in the child.

Narcotic (Opiate) Drugs
Pethidine (demerol), Morphine, Heroin (diamorphine)

This group of drugs have similar properties and effects. They are usually given as a sedatives in labour. They are not pain killing drugs, but may ease the pain indirectly as the mother becomes sedated.

Pethidine (demerol) is the most widely used, so it will be used as an example. Less is known about the effects of the other opiates on women and newborns because less research has been conducted to test their efficacy and safety.

Dosage:
The drug is supplied in prepared doses and 100mg is the commonest size, although smaller doses may be available. It should be given according to body weight. Pethidine is usually prescribed by a doctor but given by the midwife, and if a smaller dose is requested by the mother, the midwife will have to consult the doctor before the dose can be varied. 75 mg would be required for an average man when being used for post-operative pain.

It may be possible to request a smaller dose to begin, on the basis that if this is not enough, more can be administered later. Once in the system it is impossible to remove the drug except by waiting for the woman's body to eliminate the drug through her liver and kidneys (about 6 hours in a pregnant woman).

Time lag:
10-20 minutes

Duration:
2-3 hours

Route administered:
Usually by injection into the thigh or buttock. Sometimes via a drip, if one is in place.

When given:
During first stage, once labour is established. Should not be given if the birth is expected within 2 hours. Sometimes given for pain relief following Caesarean section.

Effects on the mother:
Advantages:

	1.	Sedates.
	2.	Has a secondary effect as a muscle relaxant, which ay lessen pain and reduce muscle tension, allowing faster dilatation.
	3.	May reduce pain.

Disadvantages:

	1.	Does not relieve the pain directly.
	2.	Creates a high', with feelings of floating and light-headedness that makes concentration difficult.
	3.	Some people are so sedated that drowsiness makes it difficult to cope with contractions.
	4.	Nausea, vomiting and dizziness are all common side-effects. An additional drug to counteract these effects is usually mixed with the pethidine before injection.
	5.	Depresses the mother's breathing rate, which can reduce oxygenation of the blood.
	6.	If the sedation results in a more rapid rate of dilatation than was expected, the baby may be born with more of the drug in its system than was intended.
	7.	Opiate drugs cause delayed emptying of the stomach, increasing the risks of aspiration syndrome, a serious complication, if a general anaesthetic becomes necessary.

Effects on the baby
Advantages:  None.

Disadvantages:

	1.	Pethidine crosses the placental barrier and depresses the baby's respiratory centre. This will cause breathing difficulties for the baby if it is born when the drug is at a maximum dosage in its system (between 1 and 3 hours after the injection).
	2.	An antidote to counteract the depressive effects on the baby can be given but this gives only temporary relief and the baby may still suffer breathing difficulties when the antidote wears off after a few hours.
	3.	Increased likelihood of jaundice as the baby's immature system works to eliminate the drug (and its antidote, if given). It may take 4-5 days for the baby to eliminate most of this drug from its system.
	4.	Separation of mother and baby if these problems are severe.
	5.	Difficulties establishing breastfeeding due to a depressed suckling reflex.
	6.	Research has demonstrated a potential link between exposure of some babies to pethidine during labour and their later development of an addiction to opiate drugs as teenagers.

Other drugs sometimes mixed with pethidine

These drugs are sometimes given in the same injection with pethidine or may be given separately:

• Sparine: to help enhance the action of pethidine and further reduce muscle tension.
• Stematil: to help counter the side effects of nausea and dizziness caused by pethidine.
• Maxilon: to reduce nausea and vomiting.

Nitrous oxide and oxygen (Entonox)

A combination of two gases, nitrous oxide and oxygen in provide pain relief. Many hospitals use a dispenser that allows the proportion of the gases to be varied within a given range.

Dosage:
The dosage is variable with the range from 30% nitrous oxide 70% oxygen to 70% nitrous oxide 30% oxygen. Entonox is a fixed proportion of 50% nitrous oxide and 50% oxygen.

Time lag:
15 seconds

Duration:
Only effective whilst being breathed, plus about 15 seconds longer.

Route administered:
Via a face mask, which the mother holds tightly over her mouth and nose. Deep breathing is required to activate the dispensing machine, which can then be heard making a gurgling noise. It is important to start using the mask as soon as a contraction is felt to obtain the maximum effect. The mask should be taken off the face between contractions.

A mouthpiece may be available as an alternative to the face mask.

When given:
Usually during the transition phase of labour.

Effects on the mother
Advantages:

	1.	An effective means of easing the pain, especially for the long and strong contractions of transition.
	2.	Extra oxygen can be beneficial.
	3.	Provides a distraction and a focus for attention during the turbulence of transition.

Disadvantages:

	1.	Nausea and vomiting can be side effects.
	2.	May make the mother drowsy and confused.
	3.	Some women find the face mask unpleasant, even claustrophobic.
	4.	Does not relieve the pain entirely.

Effects on the baby
Advantages:

1.

Extra oxygen could be beneficial.

Disadvantages:

1.

Research has shown a potential link between exposure of some babies to nitrous oxide during birth and their later development of an addiction to amphetamines as teenagers.