Sizing up the risks of heart-saving drugs.

Sizing up the risks of heart-saving drugs

A gold-standard therapy for heart attacks works as well as newer -- and more expensive -- clot-busters, according to interim results of a large international trial. More important, this comparison of a trio of clot-dissolvers shows that the standard treatment poses a dramatically lower risk of stroke.

"Streptokinase is safer and just as effective -- that's really the bottom line of the trial," says Peter Sleight, a cardiologist at Oxford University in England. He leads the scientists in Europe, North America and New Zealand who are conducting this ongoing trial.

At the American College of Cardiology's annual scientific sessions in Atlanta this week, Sleight's team presented data on the 42,000 heart-attack victims they are tracking. Each patient randomly received streptokinase, tissue plasminogen activator (tPA) or anisoylated plasminogen-streptokinase activator complex (APSAC) at the time of the heart attack. By dissolving blood clots in the coronary arteries, all three drugs restore blood flow to the oxygen-starved heart tissue.

People who received streptokinase infusions during the first hours of a heart attack proved as likely to survive the risky next few months as those who got infusions of tPA or APSAC.

Patients treated with streptokinase gained an unexpected benefit, however: They suffered significantly fewer hemorrhagic strokes compared to patients treated with the other two drugs. Hemorrhagic strokes, which occur when a brain blood vessel ruptures, can cause death or permanent brain damage. Ninety-four patients in the tPA group suffered such a stroke, most within 24 hours of treatment. That's about 25 percent more than in the APSAC-treated group (75) and almost 2-1/2 times as many as in the streptokinase-treated group (39).

"It appears streptokinase has the optimal benefit-to-risk ratio," says U.S. study leader Charles H. Hennekens at the Haryard Medical School in Boston.

Although some scientists had speculated tPA would prove a superior heart-attack treatment because it dissolves clots faster than streptokinase (SN: 12/12/87, p.376), this trial showed no survival edge for people getting tPA or APSAC. Indeed, the relatively new clot-busters may prove a disadvantage if they are more likely to dissolve beneficial clots in other parts of the bloodstream, such as clots repairing a breach in a brain blood vessel, Hennekens warns.

The new findings also add weight to previously voiced concerns about the high price tag of newer clot-busting agents (SN: 4/8/89, p.214). A course of tPA treatment costs about $2,200, and the typical tab for APSAC is roughly $1,700, Hennekens notes. Streptokinase, a drug that has been in use for a variety of purposes for 30 years, costs only about $200.

The cost and safety advantages may encourage more physicians -- especially U.S. clinicians who now favor tPA--to use streptokinase when treating heart attacks, the researchers say. However, Hennekens cautions, physicians should look to tPA for patients previously treated with streptokinase or APSAC.

Because they are derived from bacteria, streptokinase and APSAC are more likely to trigger an allergic reaction than tPA, which is a genetically engineered human protein, Hennekens says.