PAROXETINE

PAROXETINE
(par-ox'e-teen)
Pexeva, Paxil, Paxil CR
Classifications: psychotherapeutic agent; antidepressant; selective serotonin reuptake inhibitor (ssri);
Therapeutic: antidepressant
; ssri
Prototype: Fluoxetine
Pregnancy Category: D

Availability

10 mg, 20 mg, 30 mg, 40 mg tablets; 12.5 mg, 25 mg, 37.5 mg sustained release tablets; 10 mg/5 mL suspension

Action

Antidepressant structurally unrelated to other serotonin reuptake inhibitors. Potent and highly selective inhibitor of serotonin reuptake by neurons in CNS.

Therapeutic Effect

Efficacious in depression resistant to other antidepressants and in depression complicated by anxiety.

Uses

Depression, obsessive-compulsive disorders, panic attacks, excessive social anxiety, generalized anxiety, post-traumatic stress disorder (PTSD), premenstrual dysphoric disorder (PMDD).

Unlabeled Uses

Diabetic neuropathy, myoclonus, bipolar depression in conjunction with lithium, chronic headache, premature ejaculation, fibromyalgia.

Contraindications

Hypersensitivity to paroxetine; suicidal ideation; concomitant use of MAO inhibitors, pregnancy (category D); alcohol; children or adolescents with major depressive disorder.

Cautious Use

History of mania, suicidal ideation; anorexia nervosa, ECT therapy; seizure disorder, seizures; renal/hepatic impairment, renal failure; history of metabolic disorders; volume-depleted patients, recent MI, unstable cardiac disease; lactation. Safety and efficacy have not been established in children <18 y.

Route & Dosage

Depression
Adult: PO 10–50 mg/d (max: 80 mg/d); 25 mg sustained release q.d. in morning, may increase by 12.5 mg (max: 62.5 mg/d); use lower starting doses for patients with renal or hepatic insufficiency and geriatric patients
Geriatric: PO Start with 10 mg/d (12.5 mg/d sustained release),  [max: 40 mg/d (50 mg/d sustained release)]

Obsessive-Compulsive Disorder
Adult: PO 20–60 mg/d

Panic Attacks
Adult: PO 40 mg/d

Social Anxiety Disorder
Adult: PO 20–60 mg/d

Generalized Anxiety, PTSD
Adult: PO Start with 10 mg once daily, may increase by 10 mg/d at weekly intervals if needed to target dose of 40 mg once daily (max: 60 mg/d)
Geriatric: PO Start with 10 mg PO once daily, may increase by 10 mg/d at weekly intervals if needed (max: 40 mg/d)

Premenstrual Dysphoric Disorder
Adult: PO 12.5 mg once daily (up to 25 mg once daily) throughout the month or daily for 2 wk before menstrual period

Administration

Oral
  • Recommended initial dose with older adult, debilitated, or those with severe renal or hepatic impairment is 10 mg/d.
  • Monitor children and adolescents for changes in behavior that may indicate suicidal ideation.
  • Ensure that sustained release form is not chewed or crushed. Must be swallowed whole.
  • Be aware that at least 14 d should elapse when switching a patient from/to an MAO inhibitor to/from paroxetine.

Adverse Effects (≥1%)

CV: Postural hypotension. CNS: Headache, tremor, agitation or nervousness, anxiety, paresthesias, dizziness, insomnia, sedation. GI: Nausea, constipation, vomiting, anorexia, diarrhea, dyspepsia, flatulence, increased appetite, taste aversion, dry mouth. Urogenital: Urinary hesitancy or frequency. Hepatic: Isolated reports of elevated liver enzymes. Special Senses: Blurred vision. Skin: Diaphoresis, rash, pruritus. Metabolic: Hyponatremia in older adult. Body as a Whole: Bone fracture (in older adults).

Interactions

Drug: Activated charcoal reduces absorption of paroxetine. Cimetidine increases paroxetine levels. mao inhibitors, selegiline may cause an increased vasopressor response leading to hypertensive crisis or death. Phenytoin can cause liver enzyme induction resulting in lower paroxetine levels and shorter half-life. Warfarin may increase risk of bleeding and thioridazine levels, and prolong QTc interval leading to heart block; increase ergotamine toxicity with dihydroergotamine, ergotamine. Herbal: St. John's wort may cause serotonin syndrome (headache, dizziness, sweating, agitation).

Pharmacokinetics

Absorption: 99% from GI tract. Onset: 2 wk. Peak: 5–8 h. Distribution: Very lipophilic. 95% protein bound. Distributes into breast milk. Metabolism: Extensively in the liver to inactive metabolites. Elimination: Less than 2% is excreted unchanged in urine. 65% of dose appears in urine as metabolites. Metabolites of paroxetine are also excreted in feces, presumably via bile. Half-Life: 24 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor for worsening of depression or emergence of suicidal ideation.
  • Monitor for adverse effects, which include headache, weakness, sedation, dizziness, insomnia; nausea, constipation, or diarrhea; dry mouth; sweating; male ejaculatory disturbance. These occur in more than 10% of all patients and may result in poor compliance with drug regimen.
  • Monitor older adult for fluid and sodium imbalances.
  • Monitor those <18 y for suicidal ideation.
  • Monitor for significant weight loss.
  • Monitor patients with history of mania for reactivation of condition.
  • Monitor patients with preexisting cardiovascular disease carefully because paroxetine may adversely affect hemodynamic status.

Patient & Family Education

  • Use caution when operating hazardous machinery or equipment until response to drug is known.
  • Concurrent use of alcohol may increase risk of adverse CNS effects.
  • Adaptation to some adverse effects (especially dizziness and nausea) may occur over a period of 4–6 wk.
  • Do not stop drug therapy after improvement in emotional status occurs.
  • Notify physician of any distressing adverse effects.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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