Paxil Description:

Paroxetine or paroxetine hydrochloride is a selective serotonin reuptake inhibitor (SSRI). The antidepressant was released by GlaxoSmithKline in 1992. Since being releaed, Paxil has gone on to become one of the most prescribed antidepressants on the market.

In addition to its use in the treatment of depression, it is also prescribed for a number of anxiety disorders such as panic attacks and phobias, as well as obsessive-compulsive disorder (OCD). It was the first antidepressant formally approved in the US for treating social anxiety disorder (SAD), lending to the somewhat inaccurate referral as an “anti-shyness drug.” In the US, Paxil is also approved for the treatment of post-traumatic stress disorder (PTSD).

Classification:

SSRI

Clinical Pharmacology:

It is presumed that the efficacy of paroxetine in treating major depressive disorder, SAD, OCD, panic disorder, generalized anxiety disorder (GAD), and PTSD is linked to potentiation of serotonergic activity in the central nervous system resulting from inhibition of serotonin reuptake. Studies show paroxetine blocks the uptake of serotonin in humans. After oral administration, paroxetine is extensively metabolized.

Indications and Dosage:

Paxil is indicated for the treatment of major depressive disorder, panic disorder, obsessive-compulsive disorder, social anxiety disorder, posttraumatic stress disorder, and generalized anxiety disorder. The physician who chooses to use paroxetine for extended periods should periodically re-evaluate the long-term efficacy of the drug for the individual.

The recommended initial dosages vary depending on what condition is being treated. They are as follows:

  • Major Depressive Disorder (MDD) – 20mg/day, with or without food, usually in the morning, increases in 10mg/day increments up to a maximum of 50mg per day
  • Obsessive-Compulsive Disorder (OCD) – 20mg/day, with or without food, usually in the morning, increases in 10mg/day increments a maximum of 60mg/day (recommended dosage is 40mg/day)
  • Panic Disorder (PD) – 10mg/day, with or without food, usually in the morning, increases in 10mg/day increments at intervals of at least 1 week up to a maximum of 60mg/day (target dosage is 40mg/day)
  • Social Anxiety Disorder (SAD) – 20mg/day, with or without food, usually in the morning, no available information to suggest any additional benefit for SAD above 20mg/day
  • Generalized Anxiety Disorder (GAD) – 20mg/day, with or without food, usually in the morning, no sufficient evidence to suggest a greater benefit for GAD above 20mg/day, but may be increased in 10mg/day increments at intervals of at least 1 week up to 50mg/day
  • Posttraumatic Stress Disorder (PTSD) – 20mg/day, with or without food, usually in the morning, no sufficient information to suggest any additional benefit for PTSD above 20mg/day, but may be increased in 10mg/day increments at intervals of at least 1 week up to 50mg/day

Paxil Side Effects and Interactions:

Some studies recently have suggested that a small percentage of adolescents using paroxetine may experience increased suicidality in the early stages of treatment. Some psychologists believe that this is due to the way the drug beings to work in many patients. The first effect most individuals notice is a decrease in depression-induced lethargy and motivation. This happens before the depression actually improves, so young people may find enough “energy” and motivation to act on suicidal tendencies they may have already had.

It is important to note that adolescents prescribed Paxil are often suicidal to begin with. However, most studies comparing suicidal rates in patients using paroxetine against a control group of depressed individuals not taking paroxetine; the paroxetine group was reported to be twice as likely to commit suicide.

In patients receiving another SSRI in combination with a monoamine oxidase inhibitor (MAOI), serious, sometimes fatal reactions may occur including rigidity, myoclonus, extreme agitation, hyperthermia, delirium and coma. It is therefore strongly recommended Paxil not be used in conjunction with an MAOI, or within 14 days of discontinuing use of an MAOI. At least 2 week should pass after stopping Paxil before starting an MAOI.

Information for Parents and Kids:

Studies show that children and adolescents taking antidepressants such as Paxil may be more likely to have suicidal thoughts or exhibit suicidal behavior. If children or teenagers have been prescribed Paxil, their behavior should be carefully observed and any changes should be noted promptly, especially at the beginning of treatment or any time the dosage is changed.

Your child may develop serious symptoms suddenly, so it is important to pay attention to his or her behavior every day. Call your child’s physician immediately if your child experiences any of the following: agitation, panic attacks, extreme worry or anxiety, new or heightened levels of depression, suicidal thoughts or behavior, sleep difficulties, aggressive behavior, irrational behavior (acting without thinking), extreme restlessness, frenzied, abnormal excitement, or any other sudden, unusual changes in behavior.

Warnings and Precautions:

Individuals with major depressive disorder (MDD) – children, adolescents, or adults – may experience worsening of their depressive symptoms and/or the emergence of suicidality (suicidal thoughts or behavior) or unusual behavioral changes.

There has long been concern that antidepressants may have a role in making depression worse in certain patients, as well as contributing to suicidality. Adult patients with MDD or co-morbid depression who are being treated with antidepressants should be closely observed for clinical worsening and suicidality, especially in the beginning stages of treatment, or at times of a dose change (either decreases or increases).

Paxil should not be discontinued abruptly, as doing so may lead to a host of unwanted side effects. The medication should be instead tapered off as rapidly as is feasible.

Withdrawal:

Withdrawal symptoms from paroxetine have been reported as being generally mild and short-lived, but this opinion has been replaced by mounting concern. Around a third of users report having problems discontinuing Paxil, with symptoms such as ‘electric shock’ paraesthesia, flu-like symptoms, dizziness and auditory hallucinations.

Over-dosage & Contraindications:

Since Paxil’s introduction in America, over 300 cases of intentional or accidental overdosage have been reported the world over. These include overdoses with paroxetine alone and in conjunction with other substances. The largest known ingestion of paroxetine involved 2,000mg (33 times the maximum daily dose) in a patient who later recovered.

Commonly reported adverse reactions associated with Paxil overdose include nausea, tremor, tachycardia, confusion, vomiting, dizziness, somnolence, and coma. Other signs and symptoms associated with overdose include convulsions, ventricular dysrhythmias, hypertension, aggressive reactions, syncope, hypotension, stupor, bradycardia, dystonia, rhabdomyolysis, mydriasis, symptoms of hepatic dysfunction (including hepatic failure, hepatic necrosis, jaundice, hepatitis, and hepatic steatosis), serotonin syndrome, manic reactions, acute renal failure, urinary retention, and myoclonus.

Patients taking either monoamine oxidase inhibitors (MAOIs) or thioridazine should not take Paxil, and it is contraindicated in patients with a hypersensitivity to paroxetine or any of the inactive ingredients found in Paxil. As well, paroxetine should not be used within 2 weeks of discontinuing MAOI treatment. MAOIs should not be taken until 2 weeks after stopping treatment with Paxil.

Generic Name: paroxetine

Chemical Formula: C19H20F1NO3, Cl, 0.5 H2O

Routes of Administration: oral

Elimination Half Life: 3-65 hours (average 24 hours)

Legal Status: by prescription only

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