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Monday 01 October 2001

Autonomic responses of blood vessels and sweat glands in patients with schizophrenia treated with olanzapine or clozapine.

By: Mueck-Weymann M, Acker J, Agelink MW.

Psychopharmacology (Berl) 2001 Oct;157(4):368-72

RATIONALE: Data comparing the in vivo effects on autonomic nervous system function of standard clinical doses of olanzapine and clozapine are sparse. OBJECTIVE: The goal of this study was to compare the skin conductance response (which is peripherally mediated via muscarinic m3-receptors) and the inspiratory gasp response (which is peripherally mediated via adrenergic receptors) between healthy controls and schizophrenics treated with clozapine or olanzapine. METHODS: Twenty patients with schizophrenia (according to DSM-III-R criteria) treated with either clozapine (200-500 mg/day) or olanzapine (10-20 mg/day) as well as ten matched controls underwent simultaneous recordings of the skin conductance response (SCR) of sweat glands and of the inspiratory gasp response (IGR) of acral blood vessels. A single, deep inspiration was used as the stimulus. Group differences for the SCR amplitudes and the post-IGR redilation times were compared using the Mann-Whitney test. RESULTS: Both clozapine- and olanzapine-treated patients showed a significant SCR reduction compared to controls. Interestingly, the reduction in SCR was significantly larger in the clozapine group compared to the olanzapine group (P<0.05). Moreover, only clozapine-treated patients showed a statistical trend towards a longer IGR redilation time compared to controls. CONCLUSION: The significantly stronger SCR reduction amongst clozapine-treated compared to olanzapine-treated patients suggests that olanzapine at a standard clinical dose exhibits a significantly smaller anticholinergic effect at peripheral m3-receptors in vivo compared to clozapine. The prolongation of IGR redilation can be explained by a prolonged release of noradrenaline due to the alpha2-antagonistic effect of clozapine.

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