Paroxetine

Fass environmental information

Fass environmental information for Seroxat (paroxetine) from GlaxoSmithKline (retrieved on 2026-07-07).

Metabolism and Excretion

Paroxetine is eliminated almost entirely through metabolism. Approximately 3% is excreted unchanged, about 64% is excreted in urine as metabolites, and approximately 36% is excreted in faeces, mainly via the bile. Metabolism proceeds via an unstable catechol intermediate to three major metabolites formed through oxidation, methylation and subsequent conjugation. These metabolites cannot be converted back to the active substance and have little pharmacological activity compared with paroxetine.

Hazard

Persistence: "Ready degradability: <1% degradation in 28 days (TAD 3.11). [---] Primary metabolite (BRL36610): 50% primary degradation in 23 hrs. [---] Paroxetine is not readily degradable or inherently degradable. This substance degrades rapidly via photolysis but fate and effects data is not available for photo degradents. The phrase “paroxetine is potentially persistent in the environment” is thus chosen."

Bioaccumulation: Log D_ow at pH 7 = 1.30.

Acute toxicity: There are data for 3 trophic levels, lowest for green algae (Scenedesmus subspicatus) IC₅₀ 96h (growth) = 140 microg/L.

Risk

PEC/PNEC is based on sales data in Sweden in year 2022.

PEC = 0.025 microg/L.

PNEC = Lowest NOEC, 140 microg/L/1000 (Assessment Factor (AF) for 3 acute studies) = 0.14 microg/L.

PEC/PNEC = 0.18 which gives the risk low.

Pharmaceutical analyses of water and fish

Paroxetine has been detected in purified wastewater, surface and drinking water. In the Swedish surveillance program, paroxetine was detected up to 44 ng/L in single samples of purified wastewater.

Paroxetine has been found in wild Swedish fish, perch, at a concentration of 17 microg/kg.

Article by Richmond et al.

Paroxetine has been found in in caddisfly larvae.

Report Goodpoint 2018

Comparative assessment of environmental risk in the use of citalopram, escitalopram, sertraline, fluoxetine, venlafaxine, paroxetine and clomipramine in Sweden (Report Goodpoint 2018). Overall, there is a risk profile for the studied antidepressants.