Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PAXIL CR vs LUVOX
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
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.
Selective serotonin reuptake inhibitor (SSRI); increases serotonergic activity by blocking reuptake of serotonin into presynaptic neurons.
Major depressive disorder,Obsessive-compulsive disorder,Panic disorder,Social anxiety disorder,Generalized anxiety disorder,Posttraumatic stress disorder,Premenstrual dysphoric disorder (off-label),Hot flashes (off-label)
Obsessive-compulsive disorder (OCD),Social anxiety disorder,Panic disorder,Premenstrual dysphoric disorder (PMDD),Bulimia nervosa,Post-traumatic stress disorder (PTSD)
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.
Initial dose 50 mg orally once daily at bedtime, titrated by 50 mg increments every 4-7 days to effective dose; usual therapeutic range 100-300 mg/day divided once daily (at bedtime) or twice daily if tolerated. Maximum dose 300 mg/day.
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.
The terminal elimination half-life is approximately 15-20 hours but may be prolonged in patients with hepatic impairment or with advanced age. Steady-state is typically achieved within 7-10 days of chronic dosing.
Extensively metabolized in the liver primarily via cytochrome P450 enzyme CYP2D6. Paroxetine is a potent inhibitor of CYP2D6. Metabolites are less active and are excreted in urine and feces.
Primarily hepatic via CYP1A2; minor pathways via CYP2D6; active metabolites minimal.
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.
Approximately 94% of a dose is excreted in urine, mostly as conjugated and oxidized metabolites, with 2% as unchanged drug. Fecal excretion accounts for less than 4%.
Approximately 93-95% bound to plasma proteins, primarily alpha-1-acid glycoprotein and albumin.
Approximately 80% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein.
Apparent volume of distribution (Vd/F) is approximately 3-28 L/kg, with an average of about 13 L/kg. This wide distribution indicates extensive tissue partitioning, with brain concentrations several times higher than plasma.
The apparent volume of distribution is about 4.7 L/kg, indicating extensive extravascular distribution and tissue binding, which contributes to its long half-life.
Oral bioavailability of PAXIL CR is about 30% due to first-pass metabolism, but is lower than the immediate-release formulation (50%). Food does not significantly affect bioavailability.
Oral bioavailability is approximately 53% after a single dose, with no significant food effect. Bioavailability may be higher under steady-state conditions due to saturation of first-pass metabolism.
Creatinine clearance 30-60 m L/min: use lower end of dosing range (12.5 mg/day maximum). Creatinine clearance <30 m L/min: not recommended.
No dose adjustment required for mild to moderate renal impairment (Cr Cl ≥20 m L/min). Avoid use in severe renal impairment (Cr Cl <20 m L/min) due to lack of data.
Child-Pugh Class A or B: initial dose 12.5 mg/day, maximum 25 mg/day. Child-Pugh Class C: not recommended.
Child-Pugh Class A: no dose adjustment; Child-Pugh Class B: reduce dose by 50% (start 25 mg/day, titrate cautiously); Child-Pugh Class C: contraindicated.
Not approved for use in pediatric patients; safety and efficacy not established.
Children (8-17 years): start 25 mg orally once daily at bedtime; increase by 25 mg increments every 4-7 days to target dose; for OCD: 25-200 mg/day; maximum 200 mg/day. Weight not routinely used; dosing based on age and response.
Initial dose 12.5 mg/day; maximum 25 mg/day. Increased sensitivity to serotonin reuptake inhibition; monitor for hyponatremia and QT prolongation.
Start 25 mg orally once daily at bedtime; titrate slowly (increases of 25 mg every 1-2 weeks); usual maximum 200 mg/day due to increased sensitivity and risk of hyponatremia.
Suicidality and Antidepressant Drugs: Antidepressants increased the risk of suicidal thinking and behavior in children, adolescents, and young adults in short-term trials. Monitor closely for clinical worsening, suicidality, or unusual changes in behavior.
Increased risk of suicidal thinking and behavior in children, adolescents, and young adults with major depressive disorder and other psychiatric disorders.
Clinical worsening and suicide risk,Serotonin syndrome,Bleeding abnormalities,Activation of mania/hypomania,Seizures,Angle-closure glaucoma,Hyponatremia,Bone fractures,Discontinuation syndrome (withdrawal reactions)
Suicidality risk in young patients,Serotonin syndrome,Activation of mania/hypomania,Seizure risk,Abnormal bleeding,Angle-closure glaucoma,Hyponatremia,QT prolongation,Sexual dysfunction,Discontinuation syndrome
Concomitant use with monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuing an MAOI,Concomitant use with pimozide or thioridazine,Known hypersensitivity to paroxetine or any component of the formulation
Concomitant use with MAOIs,Concomitant use with triptans,Hypersensitivity to fluvoxamine or any excipient,Pregnancy (relative)
No specific food restrictions, but avoid excessive alcohol intake. Grapefruit has not been reported to interact significantly with paroxetine.
Avoid grapefruit juice as it inhibits CYP1A2 and can increase fluvoxamine serum concentrations, leading to toxicity. No other significant food interactions; however, taking with food may reduce GI upset.
First trimester: Increased risk of congenital cardiovascular malformations (primarily septal defects) and persistent pulmonary hypertension of the newborn (PPHN). Third trimester: Risk of neonatal adaptation syndrome (irritability, feeding difficulties, respiratory distress) and prolonged QT interval. Late third trimester exposure may cause serotonin syndrome in neonate.
First trimester: Increased risk of congenital malformations, particularly cardiac defects (RR ~1.5-2) based on observational studies; also associated with persistent pulmonary hypertension of the newborn (PPHN) (OR 2.1). Second/third trimester: Late pregnancy exposure may increase risk of preterm birth, low birth weight, and neonatal adaptation syndrome (e.g., respiratory distress, feeding difficulties, irritability).
Paroxetine is excreted into breast milk. M/P ratio is approximately 0.39. Milk levels vary; peak concentration occurs 2-4 hours post-dose. Most studies show no adverse effects in breastfed infants, but cases of irritability, poor feeding, and transient serotonin-like symptoms have been reported. Use caution; monitor infant for drowsiness, restlessness, and weight gain.
Fluvoxamine is excreted into breast milk; M/P ratio ranges from 0.29 to 0.59. Relative infant dose is approximately 1.7% of maternal weight-adjusted dose. Low risk of adverse effects in breastfed infants; monitor for drowsiness, poor feeding, and weight gain. AAP classifies as compatible with breastfeeding.
Paroxetine clearance may decrease in pregnancy, leading to higher plasma concentrations. However, dose adjustments are generally not routinely recommended due to limited data. Consider therapeutic drug monitoring if response is inadequate or side effects occur. The risk of birth defects with high doses (>30 mg/day) may be increased, so use lowest effective dose (12.5-37.5 mg/day CR). Avoid abrupt discontinuation; taper slowly postpartum.
Plasma levels of fluvoxamine may decrease during pregnancy due to increased volume of distribution and enhanced hepatic metabolism. Dose adjustment may be necessary; consider therapeutic drug monitoring to maintain efficacy. Usually, dose can be increased by 50-100% in third trimester, with gradual reduction postpartum to pre-pregnancy levels.
PAXIL CR (paroxetine extended-release) has a longer half-life than immediate-release, allowing once-daily dosing but requiring 3-4 weeks for steady state. Due to its potent CYP2D6 inhibition, use caution with tamoxifen (reduces active metabolite) and with other serotonergic drugs (risk of serotonin syndrome). Discontinuation syndrome is common; taper gradually. Pregnancy category D; avoid in third trimester due to risk of persistent pulmonary hypertension of the newborn (PPHN).
Luvox (fluvoxamine) is a selective serotonin reuptake inhibitor (SSRI) approved for obsessive-compulsive disorder (OCD) and social anxiety disorder. It has a short half-life (15-22 hours) and no active metabolites, making it suitable for patients with hepatic impairment. Monitor for serotonin syndrome, especially when co-prescribed with other serotonergic agents. Luvox is a potent inhibitor of CYP1A2, affecting metabolism of drugs like clozapine, olanzapine, theophylline, and tizanidine. Titrate slowly; start at 50 mg nightly and increase by 50 mg every 4-7 days to a max of 300 mg daily (divided for doses >100 mg). Discontinuation syndrome is common; taper gradually.
Take this medication once daily, usually in the morning with or without food. Swallow the tablet whole; do not crush, chew, or divide.,It may take several weeks to feel the full benefit; do not stop suddenly as withdrawal symptoms may occur.,Avoid alcohol while taking PAXIL CR as it can increase dizziness and drowsiness.,Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding.,Report any suicidal thoughts or unusual changes in mood immediately.,Do not take with MAO inhibitors (e.g., phenelzine) or within 14 days of stopping them.,Contact a healthcare professional if you experience symptoms of serotonin syndrome (fever, muscle stiffness, confusion, rapid heart rate).
Take Luvox exactly as prescribed, usually once daily at bedtime to minimize daytime drowsiness.,It may take several weeks to feel the full effect; do not stop abruptly without consulting your doctor.,Avoid grapefruit juice, which can increase Luvox levels and side effects.,Report any signs of serotonin syndrome (hallucinations, agitation, rapid heart rate, fever, muscle stiffness) immediately.,Do not drive or operate heavy machinery until you know how Luvox affects you, as it can cause drowsiness or dizziness.,Limit alcohol consumption; alcohol can worsen sedation and increase risk of side effects.,Store at room temperature, away from moisture and heat.
No interactions on record
"Tetracycline may inhibit the metabolism of Fluvoxamine via cytochrome P450 enzyme interference, leading to increased Fluvoxamine plasma concentrations. This elevation potentiates serotonergic effects and may precipitate serotonin syndrome, characterized by hyperthermia, autonomic instability, and neuromuscular abnormalities. Concurrent use requires careful monitoring for signs of toxicity such as agitation, confusion, and tachycardia."
"Dexlansoprazole, a proton pump inhibitor (PPI), may inhibit CYP1A2, the primary enzyme responsible for metabolizing fluvoxamine, a selective serotonin reuptake inhibitor (SSRI). This interaction can lead to increased plasma concentrations of fluvoxamine, potentiating its serotonergic effects and risk of dose-dependent adverse events such as nausea, somnolence, and serotonin syndrome. Clinicians should monitor for signs of fluvoxamine toxicity and consider dose adjustment when initiating or discontinuing dexlansoprazole."
"Afatinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, and fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), both undergo metabolism via CYP450 enzymes. Afatinib is a moderate inhibitor of CYP2D6 and may also inhibit CYP1A2 and CYP3A4, while fluvoxamine is a known inhibitor of CYP1A2 and CYP2C19. Coadministration can lead to increased fluvoxamine concentrations due to inhibition of its metabolism, potentially resulting in enhanced serotonergic effects such as serotonin syndrome, as well as increased adverse effects like nausea, dizziness, or QT prolongation."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PAXIL CR vs LUVOX, answered by our medical review team.
PAXIL CR is a SSRI Antidepressant that works by 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.. LUVOX is a SSRI Antidepressant that works by Selective serotonin reuptake inhibitor (SSRI); increases serotonergic activity by blocking reuptake of serotonin into presynaptic neurons.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PAXIL CR and LUVOX depend on the specific clinical indication. These are both SSRI Antidepressant agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of PAXIL CR is: 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.. The standard adult dose of LUVOX is: Initial dose 50 mg orally once daily at bedtime, titrated by 50 mg increments every 4-7 days to effective dose; usual therapeutic range 100-300 mg/day divided once daily (at bedtime) or twice daily if tolerated. Maximum dose 300 mg/day.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between PAXIL CR and LUVOX in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. PAXIL CR is classified as Category C. First trimester: Increased risk of congenital cardiovascular malformations (primarily septal defects) and persistent pulmonary hypertension of the newborn (PPHN). Third trimester: . LUVOX is classified as Category C. First trimester: Increased risk of congenital malformations, particularly cardiac defects (RR ~1.5-2) based on observational studies; also associated with persistent pulmonary hype. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.