The effects of citalopram (Lu 10-171) on the serotonin (5-HT) uptake kinetics in platelets from endogenously depressed patients.

The uptake kinetics of serotonin (5-HT) in platelets from eight patients with endogenous depression was determined in platelet rich plasma (PRP). From the uptake data the Scatchard correlation coefficient (r[S] ), Sips' index of heterogeneity (alpha), Km and Vmax (Lineweaver-Burk) were calculated. The measurements were performed before and after two weeks treatment with Citalopram, 1-(3-dimethylaminopropyl)-1-(p-fluorophenyl)-5-phtalan carbonitrile (Lu 10-171), a selective 5-HT uptake inhibitor. After two weeks treatment with Citalopram (5, 25 or 50 mg/day) a lowered platelet count in whole blood and PRP was observed and none of the patients had a measurable 5-HT uptake for which kinetic parameters (Km and Vmax, Lineweaver-Burk) could be calculated. However, all the patients but one improved significantly in Global score.