Cocaine users, in a test, faked out by salt solution

Regular users of cocaine are consistently unable to tell the difference between a standard dose of the $100-a-gram drug and a harmless substitute under laboratory conditions, according to experiments performed at Yale University Medical School.

A ''placebo effect'' occurred on 20 subjects, some of whom were given a strong dose of cocaine, and others who took a placebo of saline solution. Researchers said the mystique associated with cocaine encouraged users to expect certain effects, which they then experienced.