This document provides guidelines for prescribing medications during pregnancy and breastfeeding. It discusses how pregnancy causes physiological changes that can impact drug absorption, distribution, metabolism, and excretion, potentially requiring dosage adjustments. Specific medications that are considered safe to use during pregnancy are outlined, including antibiotics, analgesics, asthma medications, and treatments for common conditions like iron deficiency anemia and constipation. The document also notes that while many drugs pass into breastmilk, few are generally present in amounts that could harm infants, though some drugs like phenobarbital can concentrate in breastmilk and certain others are not recommended.

1. GENERAL PRESCRIBING GUIDELINES FOR
PREGNANCY AND BREST FEEDING

2. INTRODUCTION
During the 40 weeks of pregnancy total body water is
increased by approximately 8 liters, leading to altered
drug distribution. Pregnancy also increases cardiac
output, the rate of liver metabolism, plasma volume,
glomerular filtration and
fat stores.
concentrations
These
to be
physiological changes cause drug
reduced in pregnancy through a
combination of haemodilution and increased distribution,
metabolism and excretion.

3. Pharmacokinetic changes in pregnancy that
may require adjustments in medication
dosing or frequency
● Absorption
Slowed gastrointestinal motility may delay absorption of oral
agents.
● Renal clearance
Glomerular filtration rates increase in pregnancy to 150% of
normal range; many medications that are renally cleared require
dosage alterations in pregnancy. For example, digoxin doses
may need to be increased to as much as 1.0 mg by the end of the
second trimester.
● Hepatic clearance
An increase in hepatic clearance of pharmacologic agentsis
often seen during pregnancy.

4. ● Volume of distribution
● Plasma volume increases to 150% of normal by 24 to 28 weeks’
gestation, increasing the volume of distribution. Drugs may
require dosage adjustments.
● Protein binding
Dilution of serum proteins—caused by the increase in free
water that is responsible for most of the increase in blood
volume during pregnancy—may lead to increased free drug
levels for a particular total serum level.

5. Safer drugs during Pregnancy
● Some medications are commonly used in pregnancy. A daily
dose of 400 microgram folic acid should ideally be started pre-
conceptually and continued through the first 12 weeks of
pregnancy to reduce the risk of neural tube defects.
● Women with gastro-oesophageal reflux should be advised to
eat smaller amounts of food more frequently and avoid
aggravating, rich foods. However, antacids are often required
and can be used at any stage of pregnancy.
● Ferrous sulphate is commonly prescribed for iron deficiency
anaemia in pregnancy but alternative salt formulations can be
tried if there is poor gastrointestinal tolerance. If the response
to oral treatment is poor then women may need to be referred
for parenteral iron.

6. ● Reduced gastrointestinal motility in pregnancy can lead to
constipation. Lifestyle changes are again first-line management,
with emphasis on increasing fluids and dietary fiber. A bulk
laxative such as ispaghula and/or an osmotic laxative such as
lacunose can be safely prescribed, but stimulant laxatives
should be avoided.
● Penicillin's and cephalosporin's are considered safe to use in
pregnancy.
● Vaginal candidacies is more common in pregnancy and can be
treated with topical antifungal such as clotrimazole, but oral
antifungal agents including fluconazole, itraconazole and
terbinafine should be avoided.

7. Antibiotics that can be used in
pregnancy
Infection Suggested treatment
Urinary tract infection Cephalosporin (e.g.cefalexin).
Amoxicillin (if sensitive).
Nitrofurantoin (avoid near term).
Acute pyelonephritis Cephalosporin.
Co-amoxiclav
Chest infection Amoxicillin.
Erythromycin
Skin infection Flucloxacillin.
Penicillin V.
Erythromycin
Pelvic inflammatory disease Erythromycin plus metronidazole
Bacterial vaginosis Metronidazole.
Topical clindamycin.

8. ● Paracetamol
pregnancy.
is considered a safe analgesic throughout
For more powerful analgesia opiates such as
codeine can be prescribed, but it should be remembered that if
they are used towards term then they run the risk of inducing
neonatal respiratory depression and withdrawal syndrome.
● Low dose ibuprofen may be the safest option but generally
NSAIDs should not be prescribed.
● Lithium use is a particular concern because of the association
with congenital cardiac defects.
● Sodium cromoglycate eye drops and nasal corticosteroids can
be safely prescribed in pregnancy for hay fever.
Chorphenamine has a good safety record in pregnancy and
should be prescribed ahead of non-sedating second generation
antihistamines, such as cetirizine, on which there is less data.

9. ● Women with asthma should be strongly encouraged to
continue their medications when pregnant. Shortand
long‐acting beta‐2 agonists and inhaled steroids all
appear safe, although leukotriene receptor antagonists
such as montelukast should be continued only if they
are essential. Oral steroids should not be withheld in
cases of severeasthma.

10. Breastfeeding
● A woman's physiology returns close to within normal parameters
within days of delivery, and drug doses are usually returned to
baseline within the first three days after childbirth. Breast feeding
provides many short and long term benefits to mother and baby.
Even though many drugs pass into breast milk, few are present in
sufficient quantity to cause any adverse effects.
● Some drugs are actively secreted and concentrated into breast milk
(for example, Phenobarbital), however. Some drugs have undesirable
pharmacodynamic effects on the baby (for example, iodine in
amiodarone may cause neonatal hypothyroidism, and cytotoxics may
cause bone marrow suppression), and the immature neonatal liver
may be unable to breakdown drugs. Drug accumulation can have
undesirable effects in the baby (for example, benzodiazepines can
lead to drowsiness).

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