SURVEY SAYS MANY CARDIOLOGISTS HAVE SWITCHED FROM TPA TO
STREPTOKINASE IN THROMBOLYTIC THERAPY
ANAHEIM, Cal., Nov. 11 /PRNewswire/ -- In thrombolytic (clot- dissolving) therapy for heart attack patients, the majority of U.S. cardiologists in a recent survey said they have either switched to streptokinase from t-PA, or they are considering such a change.
The survey suggests that cardiologists are reexamining thrombolytic therapy in acute myocardial infarction (MI) in light of the findings of the Third International Study of Infarct Survival (ISIS-3). Initial results of ISIS-3 were announced at the meeting of the American Academy of Cardiology in March. The survey was completed in November.
The ISIS-3 results confirm that the world's oldest and least expensive thrombolytic agent, Streptase(R) (streptokinase), is equally effective in reducing death rates from heart attacks as the genetically engineered t-PA, and the streptokinase derivative known as APSAC, both of which may cost up to ten times more than Streptase. Thrombolytics are generally administered in the emergency room to appropriate patients presenting with acute MI.
The survey questionnaire was mailed to 2,000 randomly selected U.S. cardiologists. The statistically significant analysis is based on answers from the first 400 responding cardiologists. The survey was conducted by the T.A. Miller Company in October and November.
According to the survey, at least 59 percent of the cardiologists have either changed their choice of thrombolytic in favor of streptokinase, or they are in some way considering a change to streptokinase. A quarter (24 percent) of the respondents said that they have "already switched from t-PA to streptokinase for a great majority of patients." Another 13 percent have considered switching but have not done so yet, and 22 percent have begun to use more streptokinase, instead of t-PA.
Over 90 percent of those surveyed believe that cardiologists are reexamining thrombolytic therapy in acute MI patients. Still, six out of ten cardiologists (61 percent) prescribe t-PA on a regular basis, while 36 percent prescribe Streptase, and 3 percent prescribe APSAC (a derivative of streptokinase), according to the survey.
Most MIs are caused by clots which form in coronary arteries and block blood flow to the heart muscle. Several large scale trials have confirmed that early use of thrombolytics significantly decreases mortality from MI by about 27 percent.
Thrombolysis also has been shown to preserve ventricular function by reducing myocardial ischemia and necrosis and improving myocardial salvage. However, in the U.S., as little as one-quarter of eligible MI patients receive thrombolytic therapy.
Sixty to 70 percent of all eligible MI patients in Europe are treated with thrombolytics, most often streptokinase. In the U.S., the use of thromobolytics has been restricted to a smaller group of patients. And, currently when a thrombolytic is indicated, cardiologists tend to administer t-PA at a cost of approximately $2,200 per treatment.
In addition to being more cost effective, Streptase, $313 per dose, also appears to be safer. ISIS-3 showed significant differences among the three agents in the incidence of intracranial bleeding. Overall, the study showed that Streptase produced significantly fewer incidents of intracranial bleeding. The use of t-PA and APSAC resulted in a higher incidence of stroke, which investigators attributed to cerebral hemorrhage associated with those agents' more potent thrombolytic effects. Rates of cerebral hemorrhage in ISIS-3 were 0.3 percent for streptokinase, 0.7 percent for t-PA, and 0.6 percent for APSAC (p equals 0.00001).
ISIS-3, the largest randomized trial of a therapy ever conducted, included over 46,000 heart attack patients in more than 20 countries worldwide, with over 5,300 patients in the U.S. alone, a larger number of participants than in all other thrombolytic trials conducted in this country.
The primary endpoint of ISIS-3 mortality. The study found that there were no significant differences in the number of lives saved by each agent, with mortality rates being 10.5 percent for streptokinase, 10.3 percent for t-PA and 10.6 percent for APSAC.
As adjunctive therapy, ISIS-3 also studied the role of heparin. Heparin, which prevents clot information and consequent reinfarction by thinning the blood, is administered to enhance patency of vessels after initial reopening of coronary arteries.
Results of the earlier ISIS-2 confirmed that aspirin saves lives by reducing the incidence of reinfarctions and non-fatal strokes. Aspirin prevents the aggregation of platelets and reduces reocclusion, or the reformation of blood clots. As little as 160 mg (one-half tablet) of aspirin can provide effective protection. This dose was given to all patients in ISIS-3.
Heparin given in moderate doses by twice-a-day subcutaneous injection was effective in reducing mortality and reinfarction, thus adding a slight benefit to the aspirin and Streptase regimen. At the end of a week of heparin administration, the aspirin and heparin group had a 7.0 percent mortality incidence versus a 7.5 percent rate for aspirin alone. However, this improved mortality of 5 per 1,000 was associated with a 2 per 1,000 increase in cerebral hemorrhage.
The survey was sponsored by Astra Pharmaceutical Products, Inc. The T.A. Miller Company, Inc., is a well-known marketing research firm specializing in health care. Copies of the complete survey may be obtained by writing to the company at 1060 Clifton Avenue, Clifton, N.J., 07015.
Streptase is marketed by Astra, based in the United States in Westborough, Mass. Astra is the largest pharmaceutical company in Sweden, developing and marketing products worldwide, in the areas of cardiology, dentistry, immunology, oncology and radiology. Astra is the manufacturer and marketer of the anesthetic Xylocaine(R).
/CONTACT: David Santoriello of MCS, 908-273-9626, or at the AHA, 714-778-6600, for Astra Pharmaceutical Products/ CO: Astra Pharmaceutical Products Inc. ST: Massachusetts IN: MTC SU: SH-KW -- NY047 -- 3087 11/11/91 14:10 EST