The present invention relates to a method of treating or preventing cellular dysfunction and death caused by genetic, degenerative, toxic, traumatic, ischemic, infectious, neoplastic and inflammatory diseases and aging - and their neurological symptoms and manifestations, which includes administering d-methadone, beta-d-methadol, alpha-l-methadol, beta-l-methadol, alpha-d-methadol, acetylmethadol, d-alpha-acetylmethadol, l-alpha-acetylmethadol, beta-d-acetylmethadol, beta-l-acetylmethadol, d-alpha-normethadol, l-alpha normethadol, noracetylmethadol, dinoracetylmethadol, methadol, normethadol, dinormethadol, EDDP, EMDP, d-isomethadone, normethadone, N-methyl-methadone, N-methyl-d-methadone, N-methyl-l-methadone, l-moramide, levopropoxyphene, pharmaceutically acceptable salts, or mixtures thereof, including deuterated and tritium analogues, whether isolated from its enantiomer or synthesized de novo.
