A kit of parts containing (a) a pharmaceutical formulation including a low molecular weight thrombin inhibitor, or a pharmaceutically acceptable derivative thereof, in admixture with a pharmaceutically acceptable adjuvant, diluent or carrier, and (b) a pharmaceutical formulation including a prodrug of a low molecular weight thrombin inhibitor, or a pharmaceutically acceptable derivative of that prodrug, in admixture with a pharmaceutically acceptable adjuvant, diluent or carrier. Components (a) and (b) are each provided in a form that is suitable for administration in conjunction with the other. The kit is useful in the treatment of conditions in which inhibition of thrombin is required or desired.