paroxetine PAXIL
Class: SSRIFDA Indications: MDD, Panic Disorder, OCD, GAD, PTSD
Off-Label Use: Vasomotor Symptoms Of Menopause, Diabetic Neuropathy, Neurocardiogenic Syncope, IBS
Prescribing
Forms: 10, 20, 30, 40mg tabletDose Range: 10-60 mg/day
Starting: start at 10-20 mg qd, wait and reassess in a few weeks, then ↑ by 10mg increments weekly, max 50 mg qd
Stopping: ↓ 10 mg per day Q5-7 days with a final dose of 5-10 mg per day before discontinuation
Precautions
Contraindications: Concomitant use of MAOIsSerious Side Effects: Serotonin syndrome; ↑ risk of SI in children and young adults; may impair platelet aggregation; SIADH
Side Effects: headache, sedation/somnolence, dizziness, insomnia, decreased libido, hyperhidrosis, nausea, anorgasmia, diarrhea, constipation, weakness/asthenia, weight gain, akathisia, xerostomia
Pharmacodynamics
1° MOA: Selective serotonin reuptake inhibitor2° MOA: Weak NET inhibition
Target: SERT, NET, 5HT2A, M1, M2-5
Pharmacokinetics
t½: 21 (3-65)° TMAX: 5-6°Substrate of: 2D6
Inhibits: 2D6 (strong, dose-dependent); Induces: ∅
Active Metabolites: ∅
DDIs
- - DO NOT CO-PRESCRIBE WITH MAOIs (need a 5 t½ washout perioid)
- - 2D6 inhibitors (in addition to itself) can ↑ serum levels; as a 2D6 inhibitor itself it can increase levels of co-prescribed 2D6 substrates
Misc
- - most serotonergic SSRI → most weight gain among SSRIs
- - most anticholinergic SSRI → most sedation among SSRIs
- - NOS inhibition → most sexual dysfunction among SSRIs
- - NRI activity may confer more anxiolysis compared to other SSRIs
- - significant withdrawal if not gradually tapered
- - nonlinear pharmacokinetics; inhibits its own metabolism i.e. t½ ↑s with dose ↑s, so a 50% dose ↑ can ↑ serum levels by 100%
- - has not been implicated in QTc prolongation
Special Populations
Category C—May be less safe than than other SSRIs. Associated with cardiac malformations with high-dose, first-trimester use (other studies failed to replicate)
RID 0.5-2.8%; ∅AE's have been reported for majority of paroxetine-exposed infants
↓ clearance in the elderly; lower starting dose is recommended
Significantly affected by severe renal disease (CrCl < 30 ml/min), 4-fold ↑'s in plasma concentrations have been reported
Initial dosage should be reduced in patients with severe hepatic impairment
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