Hydroxycarbamide; Hydroxyurea

Hydroxyurea or hydroxycarbamide is an antimetabolite that inhibits DNA synthesis and is used to treat recurrent painful crises of sickle cell anaemia or sickle cell disease in patients aged two years and older, myeloproliferative syndromes (chronic myeloid leukaemia, polycythaemia vera, primary thrombocythemia, myeloid splenomegaly) and locally advanced squamous cell carcinomas of the head and neck. Oral administration in a single daily dose. 

It is excreted in breast milk in small amounts, below 10% of the relative or theoretical dose for paediatric patients, so no side effects are expected in infants whose mothers are undergoing treatment. ^{(Ware 2020, Marahatta 2017, Sylvester 1987)}

Most of the excreted drug appears within three hours of administration ^{(Ware 2020, Marahatta 2017)}. Exposure can be reduced by half, especially in infants under 3 months of age, by waiting 3 hours to breastfeed after taking the dose. ^{(Ware 2020)}

Abrupt weaning can be psychologically traumatic and harmful to the health of both the mother and the infant ^{(Pistilli 2013)}, and there is no good-quality evidence to contraindicate hydroxyurea during breastfeeding. ^{(Expert Panel 2014)}

If breastfeeding continues during prolonged treatment, it may be advisable to perform periodic haematological checks on the infant.