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 Most commonly used drugs can be safely used in women who are breastfeeding

 If prescribing a drug in a woman who is breastfeeding and you do not know whether it is safe, always seek further information

The factors that determine the transfer of drugs into breast milk are the same as that influencing drug distribution in general. Most drugs enter breast milk to a greater or lesser extent but, because the concentration has been greatly reduced by distribution throughout the mother's body, the amount of drug actually received by the breastfed baby is usually clinically insignificant.

Table 1.11 Special considerations to be made when prescribing in pregnancy.

Drugs	Considerations in pregnancy
Paracetamol	First‐line analgesic – no known adverse effects
Non‐steroidal anti‐inflammatory drugs	Can be used in first and second trimester. Avoid third trimester – can affect foetal kidneys and cause premature closure of ductus arteriosus
Corticosteroids	Prednisolone safe in pregnancy. Increased risk of gestational diabetes. If on long‐term steroids, needs parenteral therapy to cover stress of labour
Antimalarials	Hydroxychloroquine drug of choice. No known teratogenic effects. Increased risk of flare of SLE if discontinued, steroid‐sparing agent in SLE
Azathioprine	Safe in pregnancy. No known foetal effects. Useful steroid sparing agent
Sulfasalazine	Safe in pregnancy. Should prescribe 5 mg folic acid in addition to reduce risk of neural tube defects
Pencillamine/Gold	Avoid in pregnancy
Cytotoxic agents	Methotrexate and cyclophosphamide are teratogenic and should be avoided 3 months prior to conception

SLE, systemic lupus erythematosus.

Table 1.12 Drugs safe for breastfeeding mothers.

Penicillins, cephalosporins

Theophylline, salbutamol by inhaler, prednisolone

Valproate, carbamazepine, phenytoin

Beta‐blockers, methyldopa, hydralazine

Warfarin, heparin

Haloperidol, chlorpromazine

Tricyclic antidepressants

Drugs that can safely be given to breastfeeding mothers are listed in Table 1.12. Certain drugs achieve sufficient concentration in breast milk, and they are sufficiently potent that their use in breastfeeding mothers should be avoided. They are listed in Table 1.13.

Table 1.13 Commonly used drugs that should be avoided in women who are breastfeeding.

Drug	Effect of drug
Amiodarone	Iodine content may cause neonatal hypothyroidism
Aspirin	Theoretical risk of Reye's syndrome
Barbiturates	Drowsiness
Benzodiazepines	Lethargy
Carbimazole	Hypothyroidism at higher doses
Contraceptives (combined oral)	May diminish milk supply and reduce nitrogen and protein content
Cytotoxic drugs	Potential problems include immune suppression and neutropenia
Ephedrine	Irritability
Tetracyclines	Theoretical risk of tooth discoloration