Paxil is a selective serotonin reuptake inhibitor (SSRI). Paroxetine does not affect the reuptake of other central neurotransmitters. Paroxetine is a shorter acting SSRI with no active metabolite. The mechanism of action is believed to be because of the potentiation of serotonergic activity in the central nervous system resulting from inhibition of neuronal reuptake of serotonin (5-hydroxy-tryptamine, 5-HT).