The distribution was permitted under a "compassionate use" license, which allows unproven drugs to be dispensed before their effectiveness has been demonstrated in clinical trials.

They went on to conclude that Pfizer never obtained authorization from the Nigerian government to give the unproven drug to children and infants.

The F.D.A. could allow the use of unproven drugs as experiments.

B5 Availability of an unproven drug is to be increased for AIDS patients.

They also often prescribe unproven drugs.

While patients may seek unproven therapies, he said, doctors should not put themselves in the position of sanctioning treatment with unproven and potentially highly toxic drugs.

Many of these patients would have been eager to take chances with unproven drugs that showed some promise of slowing their disease, the advocates said.

They should have the option to take their chances with the new unproven drug, in this case DDI.

On March 19, the agency proposed liberalizing the use of certain unproven drugs for "immediately life-threatening diseases," though it is not known if ribavirin will be included.