Paroxetine

Brand names

• Paxil

Usage

To treat symptoms of major depression, obsessive-compulsive disorder, panic disorder, and social anxiety disorder.

How it works

Paroxetine affects levels of serotonin, a brain chemical that is thought to be linked to mood, emotions, and mental state.

Side effects

Serious

Muscle pain or fatigue, lightheadedness or fainting, rash, agitation or irritability, severe drowsiness, dilated pupils, severe dry mouth, rapid heartbeat, trembling, severe nausea or vomiting.

Common

Insomnia, dizziness, sexual dysfunction, unusual fatigue, loss of initiative, nausea or vomiting, constipation, difficulty urinating, headache, trembling.

Less common

Decreased sexual desire, blurred vision, increased or decreased appetite, weight gain or loss, heartbeat irregularities, change in sense of taste. Also tingling, prickling, or burning feeling.

Possible interactions

Other medicaments:

Paroxetine may increase the effects of:

• benzodiazepines.
• buspirone (Buspar).
• desipramine (and potentially other tricyclic antidepressants).
• dofetilide (Tikosyn) by increasing blood levels. Checks of patient clinical status and dosing changes are appropriate.
• flecainide (Tambocor) because paroxetine inhibits an enzyme system needed to remove flecainide. More frequent flecainide blood levels are prudent.
• haloperidol (Haldol), because paroxetine blocks an enzyme system needed to remove haloperidol.
• labetalol (Normodyne), and perhaps other beta blockers, because paroxetine inhibits an enzyme system needed to remove labetalol.
• minimally sedating antihistamines (astemizole and terfenadine), because paroxetine may inhibit some liver systems that usually remove them from the body.

  Paroxetine taken concurrently with:
  
  

• activated charcoal will reduce absorption of paroxetine.
• astemizole (Hismanal) may lead to heart toxicity.
• dextromethorphan (the DM ingredient in many cough suppressants) may lead to serotonin syndrome.
• digoxin (Lanoxin) may lead to lowered digoxin levels. More frequent digoxin levels are prudent.
• fenfluramine (Pondimin) may cause toxicity (serotonin syndrome).
• lithium (Lithobid, others) may lead to increased adverse effects.
• MAO inhibitors may result in a fatal serotonin syndrome.
• naratriptan (Amerge) and other triptan-type medicines may lead to loss of coordination and changes in reflexes.
• phenytoin (Dilantin) or fosphenytoin (Cerebyx) may result in decreased paroxetine blood levels and lessening of therapeutic benefits. Dose increases may be needed.
• quinidine (Quinaglute, others) may result in increased paroxetine levels and toxicity; decreased paroxetine doses may be needed.
• risperidone (Risperdal) may lead to serotonin syndrome.
• ritonavir (Norvir) may lead to paroxetine toxicity.
• sibutramine (Meridia) increases risk of serotonin syndrome.
• sumatriptan (Imitrex) can lead to hyperreflexia and poor coordination.
• tramadol (Ultram) may lead to increased risk of seizures.
• tryptophan may result in sweating, nausea and dizziness.
• venlafaxine (Effexor) can increase risk of serious serotonin syndrome.
• warfarin (Coumadin) may result in bleeding; more frequent INR (prothrombin time or protime) testing is recommended. Warfarin doses should be adjusted based on laboratory results.

The following medicament may increase the effects of paroxetine:

• cimetidine (Tagamet).

Herbal medicines or minerals:

Since paroxetine and St. John's wort may act to increase serotonin, the combination is not advised. Since part of the way ginseng works may be as a MAO inhibitor, do not combine ginseng with paroxetine. Ma huang, yohimbe, Indian snakeroot and kava kava are also best avoided while taking this medicine.

Alcohol:

The manufacturer recommends avoiding alcohol while taking this medicine.

Marijuana smoking:

Additive sedation.

Exposure to heat:

This medicine can cause excessive sweating. If you work or are frequently in a hot environment, be careful to replace enough fluids to avoid dehydration.

Heavy exercise or exertion:

Since this medicine may cause excessive sweating, be careful to replace lost fluids.

Occurrence of unrelated illness:

Fevers may cause more severe dehydration.

Discontinuation:

Do not stop this medicine without talking with your doctor. For patients taking more than 40 mg a day or who have been taking this medicine for an extended period of time, gradual dosing decreases (tapering) over several days is recommended.

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