Summary
This report describes a phase I clinical trial of a new tricyclic imipramine analogue (Leo 640) with a hydrogen atom in one of the N-methylgroups substituted by a p-chlorobensoyl. To get an objective assessment of the effects of Leo 640 we utilized the fact that tricyclic antidepressants inhibit the uptake of tyramine (thereby blocking its indirect sympathomimetic effects) and noradrenaline into peripheral adrenergic nerves. Dose-response (systolic pressor effects) curves for tyramine (TA) were established before and during treatment with Leo 640. Adrenergic nerves from the rat iris were incubated in the patient's plasma drawn immediately before the TA tests. The inhibitory effect of the endogenous plasma level of Leo 640 (and/or its metabolites) on the uptake of3H-noradrenaline (3H-NA) in these nerves was then determined. — Leo 640 was given orally in successively increasing doses (up to 1.1–5.6 mg/kg/day) to fifteen patients with various forms of depression. The duration of treatment was usually 3–4 weeks. Leo 640 caused a blockade of TA- pressor responses. Plasma of all treated patients inhibited the uptake of3H-NA in the rat iris. The results in the two tests were reasonably well correlated (p<0.01). — The results in the TA- and “rat-iris” tests were compared with those obtained with nortriptyline (NT) in the same dose-range in nine other patients. In comparison with NT, Leo 640 had a more pronounced inhibitory effect on TA-responsesin vivo than of3H-NA uptake in adrenergic nervesin vitro. A possible explanation might be that Leo 640 has an α-receptor blocking effect. — For both Leo 640 and NT, poor correlations were found between the doses (mg/kg) used and the objective effects, when different patients were compared, probably due to marked interindividual differences in pharmacokinetics. — It is concluded that the dose-range of Leo 640 should be similar to that of NT in terms of the effects onperipheral adrenergic neurons.
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A preliminary account of this paper has appeared (Siwerset al. 1969).
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Siwers, B., Freyschuss, U., Hamberger, B. et al. A quantitative approach to the initial clinical trial of tricyclic antidepressants: A comparison of Leo 640 and nortriptyline. Eur J Clin Pharmacol 3, 12–17 (1970). https://doi.org/10.1007/BF00560285
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DOI: https://doi.org/10.1007/BF00560285