Activity of citalopram on adenosine and serotonin circulating levels in depressed patients

Citalopram is a selective serotonin reuptake inhibitor used in the treatment of depression. Recent investigations have shown that it reduces in rat brain the release of excitatory amino neurotransmitters acid glutamate and aspartate by the involvement of the inhibitory neuromodulator adenosine. In this study, we described citalopram and serotonin levels in plasma and platelets, as well as plasma adenosine levels, in depressive patients during acute and chronic administration of citalopram. Twelve patients affected by Major Depression (DSM-IV) received a single oral dose of citalopram in the morning, 5 mg in the first 5 days, 10 mg from the 6th to the 10th day, and 20 mg from the 11th to the 40th day. Blood samples for citalopram, serotonin, and adenosine were collected at Time 0 and 4, 12 and 24 hours after drug administration on the first day of citalopram 5 mg, and on the first and the last day of citalopram 20 mg. Citalopram, serotonin, and adenosine concentrations in plasma increased after citalopram administration, and the highest levels were observed on the last day of treatment. Citalopram was detectable in platelets with concentrations showing a time variation similar to plasma values. Serotonin levels in platelets decreased after drug administration, reaching the lowest values on the last day of treatment.