Principles of drug administration: Administration of medicines per vaginam

Chapter 21

Principles of drug administration

Administration of medicines per vaginam

The midwife is actively involved in the administration of medicines per vaginam (P.V.), largely with prostaglandin for the induction of labour. There are a range of preparations that can be administered vaginally (tablet, creams, pessaries, foams, etc.), often used for the treatment of localized infections, contraceptive use or systemic use, e.g. prostaglandins. This chapter considers the midwife’s role and responsibilities and the procedure for administration P.V., focusing largely on the administration of prostaglandin E2 (PGE2). This chapter should be read in conjunction with Chapters 18, 29, and 30.

Advantages and disadvantages of the vaginal route

The vagina has a large surface area with a good blood supply. Medication is circulated via the internal iliac veins and therefore bypasses the liver. There are likely to be fewer peaks and troughs in plasma levels, the medication being absorbed over a given (often) slow and sustained time span. Despite these advantages, some of the disadvantages make it a less favourable route. These include:

Using prostaglandin

Naturally produced prostaglandins increase towards term and appear to both ripen the cervix and contribute towards uterine contractions (Jordan 2010). Manufactured forms of the drug can be administered for the induction of labour, per vaginam is the route of choice. Lower doses are often as effective as higher ones and little benefit is gained by repeated doses. Vaginal gel is better absorbed than vaginal tablets or pessary. It is an unstable compound chemically and so attention should be paid to correct storage (refrigerated generally) and accurate prescribing. Dosages for the different compounds, e.g. gel, tablets, or pessary, are all different, unless otherwise prescribed, they are always placed into the posterior vaginal fornix.

It is recognized that most body systems can be affected by prostaglandins. Gastrointestinal effects, e.g. diarrhoea or nausea, are common, as are flushing, hypo- and hypertension, headache and pyrexia. Some of these effects are seen within 30 minutes of administration. Serious effects such as fetal compromise, bronchospasm, uterine hypertonus, amniotic fluid embolism and uterine rupture have all been noted and care should include specific observations for these risks. Prostaglandin should be used in extreme care with grand multiparous women.

The drug begins working within 10 minutes of administration (gel is faster than pessary) but the woman is asked to retain a semi-recumbent position for 20–30 minutes to improve absorption. She should not be left alone at this time. If a retrieval device is being used, the midwife should remove the prostaglandin if any serious adverse reactions are seen, e.g. significant fetal compromise. Many women need to exercise patience when being induced, they also need to understand the range of analgesics available, prostaglandin-induced contractions often being more painful (NICE 2014).

The NICE (2008) Induction of Labour (IOL) guideline was unchanged following its review in 2014. It suggests:

Women with uncomplicated pregnancies can be offered induction of labour between 41 and 42 weeks to avoid the risks of prolonged pregnancy. There are fewer perinatal deaths, fewer meconium aspirations, and fewer caesarean sections with its use (Gulmezoglu et al 2012). Care should be woman-centred with the woman able to make a fully informed decision, being particularly aware of the risk of serious complications (NICE 2014). A plan should also be made in the event of a failed induction.

Bishop’s scoring (see Glossary) is undertaken prior to prescription and administration. With consent, membrane sweeping may be undertaken also (see Chapter 29). Depending on which of the preparations is prescribed, Bishop scoring may be repeated later and a second dose may be prescribed. If using a retrieval pessary, it should be removed when the cervix is ripened or after 24 hours, or 30 minutes before an oxytocin infusion (BNF 2014).

Electronic continuous monitoring of the fetal heart rate should be confirmed as normal prior to PGE2 administration and repeated when contractions begin. Intermittent auscultation can be used if the contraction pattern is within the sphere of normal.

Women often prefer to begin the process in the morning, although there is no evidence to suggest that this is more effective. The venue and timing of the administration should permit electronic fetal heart rate assessment. Women who have the administration of prostaglandin as an outpatient should be given clear advice regarding when to consult/return to the maternity unit (NICE 2014).

Oct 17, 2016 | Posted by in MIDWIFERY | Comments Off on Principles of drug administration: Administration of medicines per vaginam
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