Paxil

Action

Unknown. Thought to inhibit neuronal reuptake of serotonin in CNS.

Availability

paroxetine hydrochloride-

Oral suspension: 10 mg/5 ml in 250-ml bottle

Tablets: 10 mg, 20 mg, 30 mg, 40 mg

Tablets (controlled-release): 12.5 mg, 25 mg, 37.5 mg

paroxetine mesylate-

Tablets: 10 mg, 20 mg, 30 mg, 40 mg

Indications and dosages

➣ Major depressive disorder

Adults: Initially, 20 mg/day P.O. (immediate-release) as a single dose; may increase as needed by 10 mg/day at weekly intervals (range is 20 to 50 mg); daily dosages of approximately 30 mg may maintain efficacy for up to 1 year. Or initially, 25 mg P.O. (controlled-release) daily; may increase by 12.5 mg/day at weekly intervals, up to 62.5 mg/day. Or, 20 mg/day P.O. (paroxetine mesylate) as a single dose in morning; may increase as needed by 10 mg/day at weekly intervals up to maximum of 50 mg/day; daily dosages of approximately 30 mg may maintain efficacy for up to 1 year.

➣ Obsessive-compulsive disorder

Adults: Initially, 20 mg/day P.O. (immediate-release); increase as needed by 10 mg/day at weekly intervals, up to 60 mg P.O. (range is 20 to 60 mg/day). Or, initially 20 mg P.O. (paroxetine mesylate); may increase as needed by 10 mg/day at weekly intervals up to maximum of 60 mg/day; recommended dosage is 40 mg/day.

➣ Panic disorder

Adults: Initially, 10 mg/day P.O. (immediate-release); may increase as needed by 10 mg/day at weekly intervals, up to 40 mg P.O. (range is 10 to 60 mg/day); maximum dosage is 60 mg/day, with dosage adjustments made to maintain patient on lowest effective dosage. Or initially, 12.5 mg/day P.O. (controlled-release); may increase by 12.5 mg/day at weekly intervals, to a maximum of 75 mg/day. Or, 10 mg/day P.O. (paroxetine mesylate) daily in morning; may increase as needed by 10 mg/day at weekly intervals up to maximum of 60 mg/day. Target dosage is 40 mg/day. Maintain patient on lowest effective dosage.

➣ Posttraumatic stress disorder

Adults: Initially, 20 mg/day P.O.; range is 20 to 50 mg/day. Make any dosage increases if needed in increments of 10 mg/day at intervals of at least 1 week. For maintenance, adjust to lowest effective dosage.

➣ Generalized anxiety disorder

Adults: Initially, 20 mg/day P.O.; range is 20 to 50 mg/day; however, dosages greater than 20 mg/day may not provide added benefit. Make any dosage increases if needed in increments of 10 mg/day at intervals of at least 1 week. Or, 20 mg/day P.O. (paroxetine mesylate) daily in morning.

➣ Premenstrual dysphoric disorder

Adults: 12.5 to 25 mg/day P.O. (controlled-release) daily. May give either daily throughout menstrual cycle or only during luteal phase cycle (per pre-scriber). Make any dosage changes if needed at intervals of at least 1 week.

Dosage adjustment

• Hepatic impairment, severe renal impairment

• Elderly or debilitated patients

Contraindications

• Hypersensitivity to drug or its components

• MAO inhibitor use within past 14 days

• Concurrent thioridazine use

Precautions

Use cautiously in:

• severe renal or hepatic impairment

• narrow-angle glaucoma

• diseases or conditions that may affect metabolism or hemodynamic responses

• history of seizures, mania, or suicide attempt

• increased risk of suicide attempt, hyponatremia, or abnormal bleeding

• elderly or debilitated patients

• pregnant or breastfeeding patients

• children younger than age 18 (safety not established).

Administration

• Give with or without food.

• Give controlled-release tablets whole. Make sure patient doesn't chew or crush them.

☞ Don't give to patients receiving MAO inhibitors or thioridazine.

• Reassess patient periodically to gauge need for continued therapy.

Adverse reactions

CNS: anxiety, agitation, dizziness, drowsiness, asthenia, vascular headache, confusion, hangover, depression, paresthesia, tremor, twitching, myoclonus, amnesia, insomnia, abnormal dreams, unusual or severe mood changes, fatigue, cerebral ischemia, suicidal behavior or ideation (especially in child or adolescent)

CV: chest pain, hypertension, hypotension, palpitations, orthostatic hypotension, angina pectoris, ventricular or supraventricular extrasystoles, tachycardia, bradycardia, thrombophlebitis, myocardial ischemia

EENT: blurred vision, rhinitis, dry mouth

GI: nausea, vomiting, diarrhea, constipation, abdominal pain, dyspepsia, flatulence, anorexia

GU: urinary frequency, urinary disorders, urinary tract infection, genital disorders, ejaculatory disturbance, decreased libido

Musculoskeletal: back pain, myalgia, myasthenia, myopathy, joint pain

Respiratory: cough, bronchitis, respiratory disorders

Skin: sweating, pruritus, pallor, rash, photosensitivity, Stevens-Johnson syndrome (postmarketing reports)

Other: chills, edema, appetite and weight changes, accidental injury, yawning

Interactions

Drug-drug. Cimetidine: increased paroxetine blood level

Digoxin: decreased digoxin efficacy Drugs metabolized by liver (such as amitriptyline, class IC antiarrhythmics, desipramine): decreased metabolism and increased effects of these drugs 5-hydroxytryptamine receptor agonists (such as frovatriptan, naratriptan, riza-triptan): weakness, hyperreflexia, incoordination

MAO inhibitors: potentially fatal reactions (hyperthermia, rigidity, myoclonus, autonomic instability, fluctuating vital signs, extreme agitation, delirium, coma)

Phenobarbital, phenytoin: decreased paroxetine efficacy

Tamoxifen: decreased tamoxifen concentration

Theophylline: increased risk of theophylline toxicity

Thioridazine: increased thioridazine blood level, serious ventricular arrhythmias, sudden death

Tryptophan: headache, nausea, sweating, dizziness

Warfarin: increased risk of bleeding (without altering prothrombin time)

Drug-diagnostic tests. Alkaline phosphatase, bilirubin, glucose: increased levels 5-hydroxyindole acetic acid, vanillyl-mandelic acid: decreased levels

Urinary catecholamines: false increases

Drug-herbs. S-adenosylmethionine (SAM-e), St. John's wort: increased risk of adverse serotonergic effects, including serotonin syndrome

Patient monitoring

• Check for signs and symptoms of toxicity, including drowsiness, nausea, tremor, tachycardia, confusion, and dizziness.

• Assess vital signs and cardiovascular status.

☞ Monitor neurologic status. Watch closely for depression and suicidal behavior and ideation (especially in child or adolescent).

• Evaluate respiratory status. Stay alert for signs and symptoms of infection.

☞ Monitor patient for signs and symptoms of Stevens-Johnson syndrome.

Patient teaching

• Tell patient to swallow controlled-release tablets whole without chewing or crushing them.

☞ Describe signs and symptoms of drug toxicity. Tell patient to report these immediately.

☞ Teach patient or caregiver to recognize and immediately report signs of suicidal intent or expressions of suicidal ideation (especially in child or adolescent).

☞ Teach patient or caregiver to immediately report rash if it occurs.

• Tell patient to continue to take drug even if he feels better. Caution him not to stop therapy abruptly.

• Advise patient to consult prescriber before taking other prescription drugs or over-the-counter preparations.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects him.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and herbs mentioned above.