Allopurinol may increase the anticoagulant activities of Ethyl biscoumacetate. The serum concentration of Ambroxol acefyllinate can be increased when it is combined with Allopurinol. Allopurinol may increase the anticoagulant activities of Dicoumarol. The serum concentration of Theophylline can be increased when it is combined with Allopurinol. The risk or severity of adverse effects can be increased when Etacrynic acid is combined with Allopurinol. Magnesium Trisilicate can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Chlorthalidone. The risk or severity of adverse effects can be increased when Allopurinol is combined with Bendamustine. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Chlorothiazide. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Trichlormethiazide. The serum concentration of Carbamazepine can be increased when it is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Cilazapril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Ramipril. The risk or severity of adverse effects can be increased when Allopurinol is combined with Pegloticase. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Candoxatril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Fosinopril. Magaldrate can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The serum concentration of Mercaptopurine can be increased when it is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Indapamide. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Bendroflumethiazide. Allopurinol may increase the anticoagulant activities of Fluindione. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Hydroflumethiazide. Allopurinol may increase the anticoagulant activities of Phenindione. Allopurinol may increase the anticoagulant activities of Warfarin. The risk of a hypersensitivity reaction to Ampicillin is increased when it is combined with Allopurinol. Aluminium can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The serum concentration of Chlorpropamide can be increased when it is combined with Allopurinol. The risk or severity of adverse effects can be increased when Piretanide is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Spirapril. Allopurinol may increase the anticoagulant activities of Phenprocoumon. Magnesium Hydroxide can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Imidapril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Lisinopril. Aluminum hydroxide can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Cyclopenthiazide. Calcium Carbonate can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Moexipril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Zofenopril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Polythiazide. The serum concentration of the active metabolites of Azathioprine can be increased when Azathioprine is used in combination with Allopurinol. Magnesium oxide can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk or severity of adverse effects can be increased when Furosemide is combined with Allopurinol. Allopurinol may increase the anticoagulant activities of Acenocoumarol. Bismuth Subcitrate can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Enalaprilat. The serum concentration of Doxofylline can be increased when it is combined with Allopurinol. Almasilate can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Enalapril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Trandolapril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Methyclothiazide. The risk of a hypersensitivity reaction to Amoxicillin is increased when it is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Quinethazone. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Hydrochlorothiazide. The serum concentration of Dyphylline can be increased when it is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Captopril. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Metolazone. The therapeutic efficacy of Tegafur can be decreased when used in combination with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Quinapril. Sarilumab may increase the immunosuppressive activities of Allopurinol. The risk or severity of adverse effects can be increased when Torasemide is combined with Allopurinol. Sodium bicarbonate can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Temocapril. The risk or severity of adverse effects can be increased when Allopurinol is combined with Cyclophosphamide. Tromethamine can cause a decrease in the absorption of Allopurinol resulting in a reduced serum concentration and potentially a decrease in efficacy. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Omapatrilat. The risk or severity of adverse effects can be increased when Bumetanide is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Benazepril. The serum concentration of Didanosine can be increased when it is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Perindopril. The serum concentration of Aminophylline can be increased when it is combined with Allopurinol. The risk of a hypersensitivity reaction to Allopurinol is increased when it is combined with Rescinnamine.