The effects of medicinal products with similar properties such as the inotropes milrinone, enoximone, amrinone, olprinone and cilostazol may be exacerbated by anagrelide. • In vivo interaction studies in humans have demonstrated that anagrelide does not affect the pharmacokinetic properties of digoxin or warfarin. • At the doses recommended for use in the treatment of essential thrombocythaemia, anagrelide may theoretically potentiate the effects of other medicinal products that inhibit or modify platelet function e. g. acetylsalicylic acid. • A clinical interaction study performed in healthy subjects showed that co-administration of repeat-dose anagrelide 1mg once daily and acetylsalicylic acid 75mg once daily may enhance the anti-platelet aggregation effects of each drug compared with administration of acetylsalicylic acid alone.