[Medicines and lactation]

The factors that determine the transfer of medicine from mothernal blood to breast milk are the relative molecular mass of the substance, liposolubility, plasma half-life, binding to plasma proteins, pKa, the rate of metabolism and the dose taken by the breast feeding mother. The transfer of large number of medicines is small, so that the amount reaching the infant is negligible. But, certain drugs pass the milk into quantities sufficient to cause adrverse effects and these drugs should be avoided during breast-feeding. Having these facts in mind, the physician is in most cases in the position to select an appropriate medicine compatibile with breast-feeding.