Recently, a novel allelic variant of cytochrome P450 2C19 encoding ultrarapid enzyme activity was described (denoted CYP2C19*17). The objective of this study was to evaluate the impact of CYP2C19*17 on serum concentration of escitalopram in psychiatric patients. One hundred and sixty-six patients treated with escitalopram were divided into the following subgroups according to CYP2C19 genotype: CYP2C19*17/*17 (n=7), CYP2C19*1/*17 (n=43), CYP2C19*1/*1 (n=60), CYP2C19*17/def (n=16), CYP2C19*1/def (n=34), and CYP2C19def/def (n=6) (def=defective allele, i.e., CYP2C19*2 or *3). Dose-adjusted serum concentrations of escitalopram were compared using the CYP2C19*1/*1 subgroup as reference. Geometric mean of the escitalopram serum concentration was 42% lower in patients homozygous for CYP2C19*17 (P<0.01) and 5.7-fold higher in subjects homozygous for defective CYP2C19 alleles (P<0.001). Of the heterozygous subgroups, only CYP2C19*1/def was significantly different from CYP2C19*1/*1 (P<0.001). In conclusion, a homozygous CYP2C19*17 genotype is associated with lower serum concentration of escitalopram, which might imply increased risk of therapeutic failure.

A total of 149 patients in 7 centers in Denmark, Norway and Sweden entered a 6-week double-blind trial intended to assess the antidepressant effect and safety of citalopram vs placebo in depressed elderly patients (65 years of age or older) who might also suffer from somatic disorders and/or senile dementia. Results of ratings on the Hamilton Rating Scale for Depression, the Montgomery-Asberg Depression Rating Scale and the Clinical Global Impression Scale provided consistent evidence that the citalopram-treated patients improved more than the placebo-treated patients. Results of ratings on the Gottfries-Bråne-Steen dementia rating scale indicated that both cognitive and emotional functioning improved significantly more in the citalopram-treated subgroup of patients with dementia than in the placebo-treated subgroup.

These results indicate that a rapid lowering of tryptophan increases impulsiveness and decreases discriminating ability in normal individuals. The effect of 5-HT depletion on discriminating ability in this study was similar to that previously reported in depressed patients.

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A daily consumption of 7-12 cigarettes is probably sufficient for maximum induction of clozapine and olanzapine metabolism. A 50% lower starting dose of both drugs in non-smokers seems rational to avoid side effects.