622
P A R T 7
Drugs acting on the reproductive system
in response to oxytocin activity, causing water retention
by the kidney.
P
rostaglandins
Prostglandins
are used to stimulate labour or termina-
tion of a pregnancy via intense uterine contractions.
The available forms include gemeprost and dinopros-
tone. Gemeprost (
Cervagem
)
is administered via vaginal
pessary
usually for termination of pregnancy. Dinopros-
tone (
Prostin E2, Cervidil
) assists with ripening the cervix
in preparation for induction of labour and stimulates
uterine contractions. It is available as a gel or pessary.
Therapeutic actions and indications
Prostaglandins stimulate uterine activity, dislodging any
implanted trophoblasts and preventing implantation
of any fertilised egg. Gemeprost is approved for use to
terminate pregnancy in the second trimester of preg-
nancy. See Table 40.3 for usual indications for each of
these agents.
Pharmacokinetics
These drugs are well absorbed when administered. They
are metabolised in the liver and excreted in the urine.
Because of their effects on the uterus, they are used
during pregnancy only to end the pregnancy. They are
not recommended for use during breastfeeding.
Contraindications and cautions
Prostaglandins should not be used with any known
allergy to prostaglandins
to avoid hypersensitivity reac-
tions
; after 20 weeks from the last menstrual period,
which would be too late into the pregnancy for a termi
nation
; or with active PID or acute cardiovascular,
hepatic, renal or pulmonary disease,
which could be
exacerbated by the effects of these drugs.
They are not
recommended for use during breastfeeding
because of
the potential for serious effects on the neonate.
If these
drugs are to be used by a breastfeeding mother, another
method of feeding the baby should be used.
Caution should be used with any history of asthma,
hypertension or adrenal disease,
which could be exac-
erbated by the drug effects
, and with acute vaginitis
(inflammation of the vagina) or scarred uterus,
which
could be aggravated by the uterine contractions
.
Adverse effects
Adverse effects associated with prostaglandins include
abdominal cramping, heavy uterine bleeding, perforated
uterus and uterine rupture, all of which are related to
exaggeration of the desired effects of the drug. Other
adverse effects include headache, nausea and vomiting,
diarrhoea, diaphoresis (sweating), backache and rash.
■
■
Assess labour pattern, including uterine
contractions, cervical dilation and effacement, and
fetal status, including fetal heart rate, rhythm and
position. Institute electronic fetal monitoring as
appropriate.
■
■
Evaluate uterine tone, noting any indications of
atony; assess fundal height and uterine involution,
and amount and characteristics of vaginal bleeding.
■
■
Monitor the results of laboratory tests, including
coagulation studies and full blood count
to
evaluate haematological status
.
Implementation with rationale
■
■
Ensure fetal position (if appropriate) and
cephalopelvic proportions
to prevent serious
complications of delivery.
■
■
Regulate oxytocin delivery using an infusion
pump between contractions if it is being given to
stimulate labour
to regulate dose appropriately.
■
■
Monitor blood pressure and fetal heart rate
frequently during and after administration
to
monitor for adverse effects.
Discontinue the drug if
blood pressure rises dramatically.
■
■
Monitor uterine tone and involution and amount of
bleeding
to ensure safe and therapeutic drug use.
■
■
Discontinue the drug at any sign of uterine
hypertonicity
to avoid potentially life-threatening
effects
; provide life support as needed.
■
■
Monitor fetal heart rate and rhythm if given during
labour
to ensure safety of the fetus.
Evaluation
■
■
Monitor woman’s response to the drug (uterine
contraction, prevention of haemorrhage, milk
“let down”).
■
■
Monitor for adverse effects (blood pressure
changes, uterine hypertonicity, water intoxication,
ergotism).
■
■
Evaluate the effectiveness of the teaching plan
(woman can name drug, dosage, adverse effects to
watch for and specific measures to avoid them).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
Safe medication administration
Name confusion has been reported among Prostin VR
(alprostadil) and Prostin E2 (dinoprostone). Use extreme
caution to make sure that the person is receiving the correct
drug. Serious adverse effects and lack of therapeutic effects
can occur if the wrong drug is given to the person.
