Allosteric serotonin reuptake inhibitor

Allosteric serotonin reuptake inhibitor is a marketing classification invented by the pharmaceutical company Lundbeck for its selective serotonin reuptake inhibitor (SSRI) escitalopram, the S stereoisomer of the SSRI citalopram. It is based on the observation that the R isomer of citalopram can decrease the potency and inhibit the effects of the S isomer, probably through an allosteric interaction between two distinct, non-overlapping binding sites for the two different isomers on the serotonin transporter.

The term allosteric refers to the negative interaction between the binding sites of to different drugs or isomers, however, it does not relate to the action of one drug to the inhibition of serotonin uptake. Allosteric serotonin reuptake inhibitors are therefore not a therapeutically distinct class of SSRI.