Final approval has been given by the F.D.A. to distribute protease inhibitors to children. The powerful new drugs have proved, according to a variety of sources, highly successful in reducing levels of the AIDS virus' infection in adults.

After receiving extensive safety data from major drug companies, including one study that involved 51 children, the government's drug safety arm is paving the way for a variety of name-brand inhibitors that may now be marketed nationwide. These include Viracept, sold by Agouron Pharmaceuticals and Norvir, sold by Abbot Laboratories.

Children without health insurance have been receiving, under informal circumstances, dosages of Viracept for two months, according to Agouron officials. Health experts and AIDS advocates are pleased about the Government's quick response to the AIDS crisis as it affects youth. Private physicians admit that prior to the F.D.A's approval, children in their care were already receiving the new drugs.

In earlier periods, especially during the late 1980's, when fewer drugs existed to combat the virus, members of ACT UP pointed to the F.D.A's. "history of sluggishness" that was "criminally slow"giving its approval to life-prolonging drugs. This, they believe, was particularly true under moralistic Republican administrators. "Now, fortunately," believes Brian Wentworth of St. Louis, Missouri, "the F.D.A. moves much faster when human lives are at stake, especially babies' lives" Wentworth believes the F.D.A.'s present-day speed can be traced, in no small part, to ACT UP's vital militancy, which included mass demonstrations that filled the streets around F.D.A. headquarters with angry AIDS protesters.

Agouron was quick to seek concurrent F.D.A. approval for Viracept for both children and adults. The wholesale annual costs for the drug will be approximately $3,000 for children and $5,650 for adults, costs which Agouron plans to wave for children without insurance and, in some cases, for uninsured adults as well.

As of now, 10,000 American children, including teen-agers, have been infected with the virus, according to government statistics. Approximately 4,500 of these minors still live. The F.D.A. says it has approved the new drugs "under an emergency policy" that bypasses years of research if diseases are "life-threatening."

Viracept can be mixed into milk or pudding, say its makers, or it can be taken in tablet form. Both Viracept and Norvir can, in some cases, cause energy-depletion, nausea, diarrhea, and vomiting. Such side-effects, however, can be managed without difficulty by taking over-the-counter drugs.

Presently, Crixivan and Invirase, are the protease inhibitors used by adults.