Moclobemide monotherapy vs. combined therapy with valproic acid or carbamazepine in depressive patients: A pharmacokinetic interaction study

Abstract

What is already known about this subject • Moclobemide (MCB) undergoes extensive both presystemic and systemic metabolism that can be affected by concomitant drugs. • Valproic acid (VPA) and carbamazepine (CBZ) have been found to interact with psychotropic medications of all classes and many other drugs; VPA acts as a broad-spectrum inhibitor, and CBZ as a potent inducer of a variety of drug-metabolizing enzymes. • There have been no previous studies designed to investigate a potential pharmacokinetic (PK) interaction between MCB and VPA or CBZ; however, these agents are likely to be used concomitantly for the treatment of depressive disorders. What this study adds • VPA does not significantly affect PK or metabolism of MCB at steady state. • CBZ significantly decreases MCB exposure. This effect is time-dependent, being more pronounced after 3-5 weeks of co-administration. Aim: To assess the impact of valproic acid (VPA) and carbamazepine (CBZ) on moclobemide (MCB) pharmacokinetics (PK) and metabolism at steady state in depressive patients. Methods: Twenty-one inpatients with recurrent endogenous depression received MCB (150 mg t.i.d.), either as monotherapy or in combination with VPA (500 mg b.i.d.) or CBZ (200 mg b.i.d.) in a nonrandomized manner. Steady-state plasma PK parameters of MCB and its two metabolites, Ro 12-8095 and Ro 12-5637, were derived. Clinical assessments of treatment efficacy were performed weekly using standard depression rating scales. Results: CBZ, but not VPA, was associated with decreases in the MCB AUC by 35% [from 7.794 to 5.038 mg h l-1; 95% confidence interval (CI) -4.84863, -0.66194; P = 0.01] and Cmax by 28% (from 1.911 to 1.383 mg l-1; 95% CI -0.98197, -0.07518; P < 0.05), and an increase in its oral clearance by 41% (from 0.323 to 0.454 l h-1 kg-1; 95% CI 0.00086, 0.26171; P < 0.05) after 4 weeks of co-administration. MCB through concentrations were also decreased, on average by 41% (from 0.950 to 0.559 mg l-1; 95% CI -0.77479, -0.03301; P < 0.05). However, the efficacy in this group of patients was not inferior to the controls, for several possible reasons. Overall tolerability of all study medications was good. Conclusions: VPA does not significantly affect PK or metabolism of MCB, whereas CBZ time-dependently decreases MCB exposure, probably by inducing metabolism of MCB and its major plasma metabolite. The actual clinical relevance of the observed MCB-CBZ PK interaction needs to be further evaluated in a more comprehensive study. © 2008 The British Pharmacological Society.