TPA: is it worth the price?
What, then, are the relative merits of TPA and streptokinase? Existing evidence supports the concept that reperfusion rates are somewhat higher with TPA, particularly after 4 hours when streptokinase is relatively ineffective but the degree of myocardial salvage is likely to be small. Streptokinase has the major advantage of a proven track record, both in terms of improved survival and a low incidence of complications. TPA has the theoretical advantages of less activation of the systemic thrombolytic system and a shorter half-life, but the clinical relevance of these factors has not been shown and may be difficult to prove. Also, whereas a reasonable treatment protocol has been established by consensus for streptokinase, the optimal dosage and infusion time for TPA have not been defined and may be subject to individual variation. Finally, the cost of TPA is substantially higher than for streptokinase. In light of these considerations, the FDA advisory panel's recommendation to withhold approval of TPA becomes easier to understand. Clearly, additional evidence verifying the safety and efficacy of TPA is needed. If and when TPA is released, the clinician will be faced with a choice of thrombolytic agents. Assuming equal safety and efficacy, streptokinase may remain the drug of choice for most patients because of its lower cost. Finally, it is likely that the next few years will see additional refinements in TPA that may further enhance efficacy while decreasing the incidence of complications, and that a competitive market for TPA will reduce the cost. Reports of these developments are anxiously awaited.
D006801:Humans; D009203:Myocardial Infarction / Q000188:drug therapy*; D010959:Tissue Plasminogen Activator / Q000627:therapeutic use*
D010959:Tissue Plasminogen Activator