Blood and milk concentrations of ampicillin in mothers treated with pivampicillin and in their infants.

The levels of ampicillin were determined in milk and plasma of 14 lactating mothers in treatment with pivampicillin for puerperal infections and in plasma of their suckling infants. Ampicillin could not be detected in plasma of the infants, i.e. all levels were less than 0.03 micrograms/ml. Maximum levels occurred in plasma 60-120 minutes and in milk 180-240 minutes after medication. Milk-plasma ratios varied between 0.01 and 0.58. The highest level of ampicillin in milk was 1.02 micrograms/ml in a woman receiving pivampicillin tablets 700 mg t.d.s. At this level an infant can at the most ingest 0.5 mg/day. This dose is too small to cause any symptoms in the suckling infants, but allergic sensibilization through the milk is possible.