Amisulpride binds selectively to dopamine D(2) and D(3) receptors in the limbic system. Low doses of amisulpride preferentially block presynaptic D(2)/D(3)-dopamine autoreceptors, thereby enhancing dopaminergic transmission, whereas higher doses block postsynaptic receptors, thus inhibiting dopaminergic hyperactivity. Amisulpride is clinically effective on the negative symptoms of acute schizophrenia exacerbations at low dosages (50-300 mg/day), and also on the positive symptoms of the disease at high dosages (400-800 mg/day). Nineteen clinical studies involving 358 volunteers have investigated the pharmacokinetics, pharmacodynamics and tolerability of amisulpride. Amisulpride shows linear pharmacokinetics, a bioavailability of 48%, low protein binding (17%) and an elimination half-life of approximately 12 h. It is predominantly eliminated in the urine as the parent compound. It exhibits no significant detrimental effects in psychometric or memory tests up to the dose of 400 mg/day, inducing only mild impairment at high doses, whereas EEG data suggest an alertness-enhancing effect at low doses (
The pharmacodynamic interaction between mizolastine, a new H1 antihistamine, and ethanol was assessed in a randomized, double-blind, three-way crossover, placebo-controlled study. Eighteen healthy young male volunteers received mizolastine 10 mg, or cetirizine 10 mg or placebo once daily for 7 days with a 1-week wash-out interval. An oral dose of ethanol or ethanol placebo, given 2 h after dosing on days 5 or 7 of each treatment period, was administered to achieve a peak blood alcohol concentration (BAC) of 0.7 g/l then maintained for 1 h by two further doses of ethanol. Driving ability and psychomotor performance were evaluated using actual and simulated driving tests, critical flicker fusion threshold (CFF), adaptive tracking and divided attention (DAT) tasks. Ethanol produced a significant decrement in all tasks up to 5.5 h after administration: an increase in steering movements of 4.6, in lateral deviation of 0.45 m, in braking reaction time of 80 ms, in driving test and DAT performance of + 3.2; and a decrease in CFF and in tracking speed of 2.6 m.s-1. Neither mizolastine nor cetirizine significantly impaired driving ability or arousal (CFF) compared with the placebo. However, both drugs significantly impaired DAT performance 6:00 h post-dose (increase of + 2.1 for mizolastine and + 2.4 for cetirizine). The tracking speed was significantly decreased 7:50 h after mizolastine administration (-1.3 m.s-1) and more consistently from 1:30 to 7:50 h after cetirizine administration (-1.4 m.s-1). No significant adverse interaction, i.e. potentiation, occurred between ethanol and either antihistamine.(ABSTRACT TRUNCATED AT 250 WORDS)
1 The possible interaction between ao new H1 antihistamine, mizolastine, and lorazepam was assessed in a randomised, double-blind, cross-over, placebo-controlled study involving 16 healthy young male volunteers who received mizolastine 10 mg or placebo once daily for 8 days with a 1 week wash-out interval. The interaction of mizolastine, at steady-state, with a single oral dose of lorazepam or placebo was assessed on days 6 or 8 of each treatment period. 2 Psychomotor performance and cognitive function were evaluated using objective tests (critical flicker fusion threshold, choice reaction time, tapping, arithmetic calculation, body sway) and self-ratings (visual analogue scale, ARCI) before and at 2, 4, 6 and 8 h after dosing. Short-term memory (Stemnberg memory scanning, immediate free recall of a word list) and long-term memory (delayed free recall and recognition of words and pictures) were assessed before and at 3 h after dosing. Pharmacodynamic interactions were evaluated by repeated measures ANOVA in a 2 x 2 factorial interaction model. 3 Mizolastine, 10 mg once daily, at steady-state, was devoid of sedation and detrimental effect on skilled performance and memory. 4 In contrast, a single 2 mg dose of lorazepam produced marked impairment of psychomotor performance, cognitive functions (significant reduction in flicker fusion threshold, tapping and arithmetic calculation and increase in reaction times and body sway) and subjective sedation from 2 to 8 h after dosing. In addition, lorazepam induced an anterograde amnesia, characterised by a decrease in delayed free recall and recognition, and a deficit in short term memory. 5 Mizolastine did not potentiate the detrimental effect of lorazepam. The time course and the intensity of the disruption induced by the combination of lorazepam and mizolastine closely paralleled the changes induced by lorazepam alone.Keywords mizolastine lorazepam antihistamine benzodiazepine interaction psychomotor performance memory cognitive function psychopharmacology
A single oral dose of amisulpride was well tolerated and showed a similar pharmacokinetic profile in healthy elderly and young subjects. However, these findings should be confirmed after multiple dosing in a larger population in order to establish the lack of need of dosage adjustment in this elderly population.
The pharmacodynamic equipotency of 2 dose regimens (5 mg twice daily versus 10 mg once daily) of befloxatone, a new reversible and selective monoamine oxidase A (MAO-A) inhibitor, after single and multiple doses for 6 days was examined in a randomized, double-blind, three-way crossover, placebo-controlled trial of 12 healthy volunteers. Plasma levels of the deaminated metabolite 3-4 dihydroxyphenylglycol (DHPG), as measured by high-performance liquid chromatography (HPLC) with coulometric electrochemical detection, were used as an index of MAO inhibition. A single dose of befloxatone produced a significant dose-related reduction in plasma DHPG levels, as shown by the decrease in the 24-hour area under the concentration-time curve (AUC0-24) of DHPG, which peaked 2 hours after administration and persisted over 24 hours. Both dose regimens provided equipotent extent and duration of MAO-A inhibition at steady state, suggesting a once daily dosage should be sufficient for most patients. The pharmacokinetic bioavailability at steady state of both dose regimens was also similar. The concentration-time effect curve after a single dose revealed a hysteresis corresponding to the delay necessary to elicit MAO inhibition and/or elimination of DHPG. The relationship between plasma levels of DHPG and/or elimination of plasma concentrations of DHPG and befloxatone after a single dose can be modeled using the Emax model with a mean EC50 of 4.75 ng/mL, and suggests the presence of a maximal response from the single dose. This model permits prediction of steady-state levels of DHPG.
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