Food can reduce the absorption of
ampicillin by about 30%, and the peak levels and AUC of phenoxymethylpenicillin by about 50%. Limited evidence suggests that food has no significant effect on the bioavailability of flucloxacillin.
Ampicillin and phenoxymethylpenicillin should be taken one hour before food or on an empty stomach. Despite the apparent lack of interaction with flucloxacillin, it is recommended that it should be taken one hour before food or on an empty stomach to optimise absorption.