Reflexes of the cutaneous microcirculation in amitriptyline and in fluoxetine treated patients

Cutaneous microcirculation was investigated in 30 major depressed inpatients receiving either 150 mg amitriptyline (n = 15) or 30 mg fluoxetine (n = 15) as monotherapy, and in 15 normal control subjects matched for age and sex. The laser Doppler flux (LDF) was recorded while resting and under the condition of a sudden deep breath ("inspiratory gasp response"). In normal subjects this autonomic function test caused a marked decrement of LDF signal, which rapidly returned to the baseline value. In both groups of drug treated patients the decrements of LDF signal after a sudden deep breath did not differ from those found in the normal control subjects. However, in the amitriptyline-treated patients the return of LDF-signal to the baseline values was significantly delayed (P = 0.0007), while patients treated with fluoxetine showed the same behaviour as normal subjects. With a discriminant analysis using the results of the inspiratory gasp responses, 100% of the amitriptyline treated patients were correctly classified. Since both groups of depressed patients revealed comparable depression scores, the differences found are probably due to the side effects of amitriptyline. Possible clinical implications of these findings are discussed.