Orally administered racemic dl-threo-methylphenidate (dl-MPH) is widely used in the treatment of Attention-Deficit Hyperactivity Disorder (ADHD) in children and adults and also in the treatment of depression in patients suffering from cancer or AIDS, compulsive shopping disorder, narcolepsy, and hypersomnia. It is known that the therapeutic effect of dl-MPH in the treatment of ADHD in children is attributable to d-MPH (Srinivas et al, Clin. Pharmacol. Therap. 52, 561 to 568, 1992). Until recently, however, little was known about the potential pharmacological and/or therapeutic roles of 1-MPH because concentrations of 1-MPH in plasma and brain are very low due to extensive enantioselective first pass metabolism of 1-MPH after oral administration of dl-MPH (Srinivas et al, Pharm. Res. 10, 14 to 21, 1993). After intravenous administration of dl-MPH, however, both enantiomers of threo-methylphenidate are taken up into the brain although their patterns of distribution are different (Ding et al, Psychopharmacology 131, 71 to 78, 1997).
The use of oral stimulants such as dextroamphetamine or dl-MPH in the treatment of severe depressive disorders in the elderly or terminally ill depressed patients has been the subject of many studies over the years. After reviewing 85 publications on the subject, Satel and Nelson (J. Clin. Psychiat. 50, 241 to 249, 1989) were critical of the fact that many of the studies reported were methodologically unsophisticated and/or uncontrolled. They concluded that while stimulants are no more effective than a placebo in the treatment of primary depression, stimulants may be of value in the treatment of refractory patients and medically ill patients. Similarly, Chiarello and Cole (Arch. Gen. Psychiat. 44, 276 to 285, 1997) reviewed 81 publications and concluded that many of the older studies are inadequate although there was some evidence to support the use of psychostimulants in selected clinical instances. Emptage and Smith (Annals of Pharmacotherapy, 30, 151 to 157, 1996) reviewed 43 studies published from 1986 to 1995 and concluded that oral -MPH appears to be a safe and effective treatment for depressed, medically ill, elderly patients to provoke a rapid onset of antidepressant activity. Recently Wallace and co-workers (Am. J. Psychiat. 152, 929 to 931, 1995) conducted what they termed the first placebo-controlled double blind trial to demonstrate the efficacy of oral dl-MPH in older, medically ill depressed patients. The benefit of oral dl-MPH was statistically and clinically significant despite the small number of patients in the study (n=16). Depressive symptoms decreased markedly in 7 subjects (Hamilton depression scale decreased by &gt;55%), moderately in a further 3 subjects (Hamilton depression scale decreased by 30 to 55%), minimally in 3 subjects (Hamilton depression scale decreased by &lt;30%) and three patients were dropped from the study.