Comparative Pharmacology
Head-to-head clinical analysis: PAXIL versus PAXIL CR.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PAXIL versus PAXIL CR.
PAXIL vs PAXIL CR
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Paroxetine is a selective serotonin reuptake inhibitor (SSRI) that potentiates serotonergic activity in the central nervous system by inhibiting the reuptake of serotonin (5-HT) from the synaptic cleft, leading to increased serotonin levels.
Paroxetine is a selective serotonin reuptake inhibitor (SSRI). It potentiates serotonergic activity in the CNS by inhibiting the reuptake of serotonin at the presynaptic neuronal membrane, resulting in increased serotonin concentrations in the synaptic cleft.
20 mg orally once daily, typically in the morning; may be increased in 10 mg/day increments at intervals of at least 1 week to a maximum of 50 mg/day.
12.5-37.5 mg orally once daily in the morning; initial dose 12.5 mg/day, titrate by 12.5 mg/day at intervals of at least 1 week to maximum 50 mg/day.
None Documented
None Documented
Mean terminal half-life 21 hours (range 3–65 hours); steady-state achieved within 7–14 days; nonlinear kinetics with dose increase leading to disproportionate increases in half-life due to saturable hepatic metabolism (CYP2D6).
The terminal elimination half-life of paroxetine (PAXIL CR) is approximately 15-20 hours. This supports once-daily dosing and requires about 5-7 days to reach steady-state concentration.
Renal: 64% (2% unchanged, 62% as metabolites); Fecal: 36% via bile; urinary excretion of unchanged paroxetine <2%.
Renal excretion accounts for approximately 64% of the administered dose, with 2% as unchanged parent drug and the remainder as metabolites. Fecal excretion accounts for about 36%, mostly as metabolites. Less than 1% is excreted in bile.
Category C
Category C
SSRI Antidepressant
SSRI Antidepressant