A dose-response study of scopolamine in major depressive disorder

INTERVENTION: Arm 1: A single intravenous infusion of 4 µg/kg scopolamine hydrobromide given over 15 minutes under clinical observation Arm 2: A single intravenous infusion of 5 µg/kg scopolamine hydrobromide given over 15 minutes under clinical observation Arm 3: A single intravenous infusion of 6 µg/kg scopolamine hydrobromide given over 15 minutes under clinical observation CONDITION: Major Depressive Disorder; ; Major Depressive Disorder Mental Health ‐ Depression PRIMARY OUTCOME: Total score of the Montomery‐Asberg Depressive Rating Scale (MADRS)[24 hours post administration. Additional assessments are made at baseline, 2 days, 7 days, 14, days, 28 days and 42 days.] SECONDARY OUTCOME: Total score of the Quantitative Inventory of Depressive Symptomology [24 hours post administration. Additional assessments are made at baseline, 2 days, 7 days, 14, days, 28 days and 42 days.] INCLUSION CRITERIA: • Major depressive disorder for at least three months, as assessed by both Clinical Interview using and the Mini‐International Neuropsychiatric Interview (MINI) • A pre‐trial Montgomery‐Asberg Depression Rating Scale score of greater than 20 • Male or female, aged 18 years or above and less than 60. • In the Investigators’ opinion, is able and willing to comply with all trial requirements. • Participant is willing and able to give informed consent for participation in the trial.