Following administration of ampicillin to pregnant women a transient decrease in plasma concentration of total conjugated oestriol, estradiol has been noted. This effect may also occur with amoxicillin and therefore with Co-amoxiclav. Probenecid decreases the renal tubular secretion of amoxicillin but does not affect clavulanic acid excretion. Concurrent use with Co-amoxiclav may result in increased and prolonged blood levels of amoxicillin but not to clavulanic acid. The concurrent administration of allopurinol and ampicillin increases substantially the incidence of rashes in patients receiving both medicines as compared to patients receiving ampicillin alone. It is not known whether this potentiation of ampicillin rashes is due to allopurinol or the hyperuricaemia present in these patients. No information is available about the concurrent use of Co-amoxiclav and Alcohol. However, the ingestion of alcohol while being treated with the beta-1 lactam antibiotics latamoxef, cefoperazone and cephamandole has precipitated a disulfiram (Antabuse) like reaction in some patients. Therefore the ingestion of alcohol should be avoided during and for several days after treatment with Co-amoxiclav.