Relevance of plasma levels during clomipramine treatment of primary depression

Monitoring of tricyclic antidepressant plasma levels and clinical response: a review of the literature. Part II

Part II of this paper contains some general considerations on tricyclic antidepressant (TCA) monitoring. Long-term assessment of TCA plasma levels is advised by the few existent studies, although each of these focusses on different aspects. Cardiovascular and central nervous system toxicity is reviewed as well as pharmacokinetics and the importance of protein binding. Some consideration is also given to their use in elderly patients. The authors conclude that although available data support its usefulness in many situations, routine measurement of TCA levels is not warranted.

Clomipramine metabolism. Model-based analysis of variability factors from drug monitoring data

A steady-state model is here developed as a framework for the analysis of blood concentrations of clomipramine, obtained during routine drug monitoring. A model is proposed to account for its major metabolic pathways, hydroxylation and demethylation, including first-pass effect. Impaired hydroxylation capacity is shown to lead to a dramatic increase in the concentration of demethyl-clomipramine, with a concomitant moderate increase in that of the parent drug. Deficient demethylation capacity is associated with a reduced ratio of demethyl metabolite to parent drug. A nomogram is provided to allow easy determination of hydroxylation and demethylation capacities from routinely measured blood concentrations. Data from 150 patients are analysed in order to identify interindividual variability factors. Average pseudo-clearances, calculated from trough blood concentrations at steady-state, are 17 L/h for hydroxylation, 23 L/h for demethylation and 40 L/h for elimination of hydroxylated metabolites. Maximum to minimum ratios are 8, 27 and 11, respectively. The metabolising capacity through either process significantly decreases with increasing age, clearance estimates being 40 to 50% lower for patients 75 years or older than for those 40 years or younger. Tobacco smoking and chronic alcohol consumption induce and reduce the demethylation clearance, respectively. Inhibition of hydroxylation in the presence of phenothiazine comedication is also shown. Finally, small but significant differences according to sex are observed. Potential implications of the proposed model-based approach include adaptation of the dosage regimen to individual characteristics at the very beginning of antidepressant therapy, and early detection of patients with impaired metabolising capacities.

Acute antidepressant effect of lithium is associated with fluctuation of calcium and magnesium in plasma. A double-blind study on the antidepressant effect of lithium and clomipramine

In a double-blind study on 22 patients with major depressive disorder the effects of lithium and clomipramine on signs and symptoms and on calcium and magnesium in plasma were compared. Ratings of antidepressant and side effects were performed by 2 psychiatrists at the end of a placebo period of 5-7 days and after treatment for 2 and 4 weeks. Psychopathology was rated by 15 reported and 4 observed items from the Comprehensive Psychopathological Rating Scale (CPRS). Eleven items present in 72-100% of the patients were used to evaluate the effect of the two drugs. After 2 weeks of treatment the rated scores dropped for more than half of the CPRS items. After 4 weeks the scores for all but one item were reduced in both groups. The sums of scores were significantly reduced after 2 weeks in both groups and after 4 weeks global scores were reduced as well. The drugs had notable and similar antidepressant effects. Lithium treatment was associated with fluctuations in calcium and magnesium levels in plasma not seen during clomipramine treatment. Serum prolactin increased during clomipramine treatment but was unaffected by lithium treatment. No correlations were found between the sum of rating scores and blood levels of drugs, prolactin, calcium or magnesium.

Plasma levels and clinical response during treatment with clomipramine

The plasma levels of clomipramine (CI) and its major metabolite desmethylclomipramine (DMCI) may be related to clinical response during treatment of depression. Not all workers have been able to demonstrate such a relationship. The many factors which may affect clinical response include sample selection, assessment and its quantification and kinetic factors. A further investigation into the relationship between plasma levels and response was, therefore, carried out taking these into account and attempting to control them. Sixty-two patients with depressive illness were included. The plasma levels of CI + DMCI as measured on the 28th day of treatment were correlated against clinical response at the time. Patients with the highest combined plasma levels showed the best response. Patients with intermediate plasma levels showed more modest response, whilst lowest plasma levels tended to be shown by patients who exhibited an inadequate response or who relapsed during subsequent outpatient follow-up. The threshold value for satisfactory antidepressant effect appeared to be a combined CI + DMCI plasma level of 160-200 mg/ml.