The Food and Drug Administration Friday proposed making an unapproved drug for Alzheimer's disease available to more patients stricken by the devastating disease by conducting a large study of its effectiveness.

Dr. Paul Leber of the FDA's division of neuropharmacological drugs products recommended the new study of tacrine, or THA, in a letter to the Parke-Davis Pharmaceutical Research Division of the Warner Lambert Co., the drug's maker.The Morris Plains, N.J., company failed last week to convince an FDA advisory panel to recommend approving the drug, which would be sold as Cognex. The committee said there was not enough evidence of the drug's effectiveness.