Motapizone is a pyridazinone derivative patented by pharmaceutical company Nattermann, A., und Cie. G.m.b.H. as an antithrombotic and hypotensive agent. Motapizone ats as a potent inhibitor of the isoenzyme phophodiesterase type III. In preclinical studies potent antithrombotic and hypotensive properties of motapizone has been shown in rats, cats, and dogs. In normal human volunteers, single oral doses of motapizone up to 10 mg produced significant inhibition of platelet aggregation measured by the ex vivo method. These effects were dependent upon the dose of motapizone and associated with an increase in heart rate and a reduction in diastolic blood pressure.