The U.S. Food and Drug Administration asked two American contraceptive researchers to "immediately halt" all distribution of quinacrine pellets, which have been used to irreversibly sterilize women in the Third World. An Oct. 14 warning letter to the two Americans, Dr. Elton Kessel and Stephen D. Mumford, said the agency had concluded that quinacrine used for sterilizations is an "unapproved new drug" and an "unsafe use of this drug product."