The Food and Drug Administration has confiscated more than 1 million "pep pills" from three pharmaceutical companies as part of a new federal effort to force the makers of so-called look-alike drugs out of business.

The pills, which have become popular among teen-agers and college students, contain three non-prescription ingredients: caffeine (a stimulant), phenylpropanolamine (an appetite suppressant) and ephedrine (a decongestant). Taken separately, those ingredients are safe, but when mixed together and taken in large doses or with alcohol, the ingredients can be dangerous, the FDA said. Since 1980, the pills have been linked to 14 teen-age deaths.

Even though FDA already had ruled that the three ingredients were safe, it notified 16 companies last month that they must submit the pills for FDA approval or stop making them. The triple combination, FDA explained, makes the pills a "new drug." The agency also told the companies that it was doubtful that their products would be approved since the triple combination "serves no medical purpose" and is an "irrational combination."

Agents seized the tablets and more than $100,000 worth of machinery from Pharmafair Inc. and Pharmaceutical Dynamics Inc., both of Hauppauge, N.Y.; and from B. T. Products Inc. of Tampa.