Resistant geriatric depressions and therapeutic response to monoamine oxidase inhibitors.

Elderly depressed patients who met the research diagnostic criteria (RDC) for major depressive illness, resistant to other types of treatment, were treated with phenelzine, a nonselective monoamine oxidase (MAO) inhibitor, for a period of 2 to 7 weeks, following 2 weeks of placebo washout period. Dosage ranged from 15-75 mg daily. Clinical status of patients as well as vital signs, EKG, and platelet MAO inhibition were measured weekly. All responders at the end of this period were followed for 1 to 2 years. Analysis of the results showed a 65% response rate as measured by Hamilton, Global, and Self-rating Scales. No significant drug effect in cognitive functioning, as measured by objective cognitive tests, was observed. Clinical improvement was sustained for all participants throughout the follow-up period with no side effects. A direct relationship between platelet MAO inhibition and clinical response was found. The majority of the responders (70%) had achieved high platelet MAO inhibition values (greater than 80%), while most of the nonresponders had platelet MAO inhibition values of less than 80%. These findings have potential clinical and research implications for treating geriatric depression, especially the ones resistant to other forms of treatment.