Possible Relations of Hypoglycaemia Induced by Mono-amine Oxidase Inhibition and Angina Pectoris. †

The initially favorable results of the value of the mono-amine oxidase inhibitors in treatment of angina pectoris have latterly been tempered by further experiences of their use(l), and the response to therapy is probably, at best, unpredictable. However, it is of interest that Weiss et al.(2), using one of these drugs, iproniazid, in treatment of depressive patients, showed that those patients whose appetite, weight and sense of well being improved, demonstrated a definite hypoglycaemic response to the drug. It occurred to us that a similar correlation with hypoglycaemia may also exist in patients who showed improvement in the symptoms of angina pectoris as a result of such treatment. In considering the nature of this hypoglycaemia, the ganglion blocking action of iproniazid (3) may have resulted in a type of hypoglycaemic insensitivity due to inhibition of sympathetic discharge to the adrenal medulla and liver, such as follows hexamethonium therapy(4): or secondly, the slight galactose intolerance noted by Weiss et al. may have been a factor in production of hypoglycaemia, since it is known that an increased blood galactose may have some hypoglycaemic action in the normal individual(5). To try to elucidate these points it was decided to compare the response of total blood sugar and blood glucose levels to a mixed oral dose of glucose and galactose under the influence of ganglion blockade from mecamylamine, and mono-amine oxidase inhibition from iproniazid and nialamide respectively. The latter, unlike iproniazid, produces only minimal postural hypotension (6).

Methods. The following carbohydrate tolerance test was performed in all subjects. A fasting venous blood sample was collected. then a mixture of 25 g glucose and 25 g galactose in 250 ml water was given by mouth. Further venous samples were withdrawn 10, 20, 30, and 45 minutes later.