Prolongation of bleeding time and prothrombin time have been reported in some patients receiving Coamoxiclav. In common with other broad-spectrum antibiotics, Co-amoxiclav may reduce the efficacy of oral contraceptives and patient should be warned accordingly. Concomitant use of allopurinol during treatment with amoxycillin can increase the likelihood of allergic skin reactions. There are no data on the concomitant use of Co-amoxiclav and allopurinol.