Paxil

Class: Selective serotonin reuptake

inhibitors (SSRIs)

paroxetineTrade names: Paxil, Paxil CR

Most Common

UsesMajor depressive disorder, panic disorder, obsessive compulsive disorder (OCD), generalized anxiety disorder (GAD), social anxiety disorder, Post-traumatic stress disorder (PTSD), Premenstrual dysphoric disorder (PMDD).

Dosing RegimineDEPRESSION

Adults: PO 20mg- mg (single dose in morning)

Geriatric/Debilitated Patients: PO 10mg/day initially; may be slowly increased (not exceeding 40 mg/day)

Mechanisms of Action

It is thought at SSRIs work on easing depression by blocking the reuptake of serotonin at the synapse.

This allows more serotonin to remain in the synaptic cleft where it can then bind/activate receptors

How Paxil Works

Pharmokinetics

CNS: Neuroleptic Malignant Syndrome (life-threatening neurologic disorder), Suicidal thoughts, anxiety, dizziness, drowsiness, headache, insomnia, weakness.

GI: constipatuon, diarrhea, dry mouth, nausea

GU: ejaculatory disturbance

Derm: Sweating

Misc: Serotonin Syndrome (life-threatening drug reaction)

Absorption: Completley absorbed following oral admin. CR tablets are enteric-coated

and control medication release over 4-5 hr.

Distribution: Widely distributed thoughout body fluids and tissues, including CNS; cross the placenta nd enter beast milk.

Protein Binding: 95%

Metabolism and Excretion: Highly metabolized by the liver (partly by P450

2D6 enzyme system); 2% excreted unchanged in urine.

Half-life: 21 hr

Adverse Effects

Drug-Drug Interactions

Serious, potentially fatal reactions may occur with concurrent MAO inhibitor therapy. MAO inhibitors should be stopped at least 14 days prior to paroxetine therapy. Paroxetine should be stopped at least 14 days prior to MAO inhibitor therapy.

May ↓ metabolism and ↑ effects of certain drugs that are metabolized by the liver, including other antidepressants, phenothiazines, class IC antiarrhythmics, risperidone, atomoxetine, theophylline, procyclidine, and quinidine. Concurrent use should be undertaken with caution.

Concurrent use with pimozide or thioridazine may ↑ risk of QT intercal prolongation and torsades de pointes. Conccurent use is contraindicated.

Cimetidine ↑ blood levels.

Phenobarbital and phenytoin may ↓ effectiveness.

Concurrent use with alcohol isn’t recommended.

May ↑ risk of bleeding with warfarin, asprin or NSAIDS.

Concurrent use with 5-ht1 agonists, linezolid, lithium, or tramadol may result in ↑ serotonin levels and lead to serotonin syndrome.

↑ risk of serotonergic side effecrs including serotonin syndrome with St. John’s wort, SAMe, and tryptophan.