ALPROSTADIL - AN EFFECTIVE ANTIPLATELET AGENT FOR CALVES

Aspirin and other nonsteroidal, antiinflammatory drugs inhibit human p latelets, but their effect as an antiplatelet agent on bovine platelet s is not certain. Since calves are used for cardiovascular implant res earch, need exists for an effective antiplatelet agent for this animal model. After screening a number of potential antiplatelet drugs for c alves, Alprostadil (prostaglandin E(1)) appeared to be the most promis ing. Alprostadil was administered (intravenous continuous drip) to 8 c alves. The concentration of the drug administered was gradually increa sed until 50% inhibition of platelet aggregation was obtained. Platele t function, blood pressure, body temperature, and hematologic paramete rs were closely monitored. For in vitro evaluation, Alprostadil was ad ded to human or bovine blood, and the platelet aggregation and cyclic adenosine monophosphate levels were measured. Alprostadil inhibited bo th bovine and human platelets, although bovine platelets were relative ly more responsive to this drug. At an infusion rate of approximately 0.20 mu g/kg/min in vivo, Alprostadil showed 50% inhibition of platele t aggregation with slightly decreased blood pressure (7 +/- 6 mm Hg) b ut no adverse effects. Complete reversal of in vivo platelet inhibitio n was noted within 24 h after cessation of drug administration. This s hort half-life and the lack of significant adverse effects make Alpros tadil an attractive antiplatelet agent for calves with cardiovascular implants.