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Paroxetine (Paxil)

SSRIprescriptionoral · inferred

Most potent SSRI for serotonin reuptake inhibition, also with mild norepinephrine reuptake inhibition and significant muscarinic anticholinergic activity. Inhibits its own CYP2D6 metabolism (nonlinear pharmacokinetics), small dose increases can produce disproportionately higher serum levels. More weight gain and sexual dysfunction than other SSRIs. Difficult discontinuation syndrome due to short half-life and anticholinergic rebound. Not recommended in pregnancy (Category D).

Projected serum levels — 20 mg, once daily

Paroxetine (Paxil)
Paroxetine (Paxil) modeled serum levels, 20 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 3 days. 0 5 10 15 20 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 3
Paroxetine (Paxil) modeled serum levels with a loading dose of 37.2 mg, then 20 mg once daily The first dose is larger so levels approach steady state faster. 0 5 10 15 20 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 20 mg once daily (oral).

Loading schedule: 37.2 mg on day 1, then 20 mg once daily — reaching therapeutic levels sooner.

Modeled steady state after ~3 days: peak ≈ 15.6 mg, trough ≈ 8.4 mg body load. Population-based estimate over 15 days for a 20 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
SSRI
Route modeled
Oral
Model confidence
inferred
Half-life
21 h
Common dose
20 mg
Suggested maximum
60 mg/day
Reference dose range
10–60 mg (single dose)
Suggested cadence
once daily
Validated against
20 mg oral — Cmax 0.030 mg/L at 5 h

Documented interactions

  • contraindicated
    6-APB (Benzofury / 6-(2-aminopropyl)benzofuran) + Paroxetine (Paxil) CYP inhibition

    Paroxetine (Paxil) mechanism_based of CYP2D6 predicted to change 6-APB (Benzofury / 6-(2-aminopropyl)benzofuran) AUC by ~10.00x

  • contraindicated
    Atomoxetine (Strattera) + Paroxetine (Paxil) CYP inhibition

    Paroxetine (Paxil) mechanism_based of CYP2D6 predicted to change Atomoxetine (Strattera) AUC by ~5.14x

  • contraindicated
    DOM (2,5-Dimethoxy-4-methylamphetamine / STP) + Paroxetine (Paxil) CYP inhibition

    Paroxetine (Paxil) mechanism_based of CYP2D6 predicted to change DOM (2,5-Dimethoxy-4-methylamphetamine / STP) AUC by ~10.00x

  • contraindicated
    Ibogaine + Paroxetine (Paxil) CYP inhibition

    Paroxetine (Paxil) mechanism_based of CYP2D6 predicted to change Ibogaine AUC by ~10.00x

  • contraindicated
    Metoprolol (Lopressor / Toprol-XL) + Paroxetine (Paxil) CYP inhibition

    Paroxetine (Paxil) mechanism_based of CYP2D6 predicted to change Metoprolol (Lopressor / Toprol-XL) AUC by ~5.14x

  • danger
    1P-LSD (1-Propionyl-LSD) + Paroxetine (Paxil) Serotonin risk

    1P-LSD (1-Propionyl-LSD) and Paroxetine (Paxil) both have serotonergic activity. Risk of serotonin syndrome (hyperthermia, rigidity, autonomic instability, altered mental status).

Serum checks 254 modeled interaction pairings for paroxetine (paxil) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Paroxetine treatment of generalized anxiety disorder: a randomized, controlled trial Rickels K et al. · American Journal of Psychiatry, 2003 DOI

    Large RCT (566 patients) demonstrating paroxetine 20-50 mg/day significantly reduced GAD symptoms versus placebo, with 68% response rate at 8 weeks and efficacy maintained in long-term extension.

  2. Paroxetine in the treatment of panic disorder: a randomized, double-blind, placebo-controlled, dose-escalation study Ballenger JC et al. · British Journal of Psychiatry, 1998 DOI

    Multicenter RCT establishing paroxetine 40 mg/day as significantly superior to placebo for panic disorder, with 51% of patients panic-free versus 32% on placebo at 10 weeks.

  3. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder Cipriani A et al. · Lancet, 2018 DOI

    Network meta-analysis of 522 trials ranked paroxetine as effective for depression but with lower acceptability than escitalopram and sertraline, consistent with its higher side-effect burden.

3 published studies referenced in the app, each with a plain-language summary.