Preliminary results with rubidium in depressed patients

Lithium and Rubidium are closely linked in their history as far as their the rapeutic use in psychiatry is concerned. The introduction of rubidium into human therapy during the 19th century was mainly directed towards the treatment of several pathological conditions, also including epilepsy and syphilis, but not mental illnesses, despite the early observation of Botkin (1). This author occasionally reported that several of his cardiac patients, treated with approximately 1.6g of rubidium showed a subjective feeling of well-being. Following this observation, 80 years passed before a controlled study on the psychiatric effects of rubidium was carried out. This study was undertaken as a consequence of the excellent results obtained with lithium in the therapy and prophylaxis of manic-depressive psychosis. It was shown that rubidium increased EEG frequency and behavioural activity in monkeys (2) and consequent to opposite results obtained with lithium, the authors suggested that rubidium might have a clinical application in the treatment of affective disorders. Subsequently, several observations led to the assumption that rubidium and lithium have opposite behavioural, electroencephalographic and biochemical properties (3, 4, 5, 6, 7, 8), thus further defining the potential antidepressant activity of the former. The possible clinical activity of rubidium has been investigated by early studies of Meltzer and Fieve (9, 10, 11, 12). These authors studied 25 depressed patients resistant to other treatments, affected by either unipolar or bipolar syndromes. The experimental design consisted of a cross-over study with placebo or rubidium for a period of 2 to 4 weeks. Blood rubidium levels reached 0.44 mEq/1. Positive response varied depending on the duration of treatment: 70% after 4 weeks, 57% after 3 weeks, 45% after 2 weeks. Subsequently, a single blind study in which rubidium was compared to imipramine was carried out (13). Thirty depressed patients (endogenous, reactive, neurotic or involutional) received rubidium chloride for 4 weeks at a maximum dosage of 540mg per day. The salt improved 65% of these patients, acting in particular on depressive mood and psychomotor retardation as well, and did not produce any specific side effects. Two studies on the effect of rubidium in chronic schizophrenics were carried out in Canada, at the McGill University (14, 15). The treatment consisted of single administration of 1g of rubidium chloride in addition to the usual neuroleptic regimen. The results of these studies underlined a slight beneficial effect of the salt on emotional withdrawal and motor retardation without producing any toxic reaction or altering EEG, EKG, or routine laboratory tests.