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Paxil (Paroxetine) Medication
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Basic information
- Generic name: Paroxetine hydrochloride
- Brand/Trade names: Paxil, Paxtine
- Dosages:
Tablets 10 mg, 20 mg, 30 mg, 40 mg;
Suspension, oral 10 mg per 5 mL
Tablets, controlled-release 12.5 mg, 25 mg, 37.5 mg
- Pharmacologic category: Selective serotonin
reuptake inhibitor
- FDA approved: December 29, 1992
- Manufacturer: GlaxoSmithKline
- Habit forming? No
- Pregnancy risk factor: D
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Medical uses
Paxil (Paroxetine hydrochloride) is an agent in a newer class
of antidepressant medication known as selective serotonin reuptake
inhibitors (SSRIs).
This antidepressant medication has been approved by the U.S. Food
and Drug Administration as a safe and effective treatment for
these conditions:
- Depression
- Generalized Anxiety Disorder (GAD)
- Social Anxiety Disorder
- Panic Disorder
- Obsessive Compulsive Disorder (OCD)
- Posttraumatic Stress Disorder (PTSD)
With continued treatment, Paxil can help restore the balance
of serotonin (a naturally occurring chemical in the brain) - which
helps reduce the symptoms of anxiety and depression.
When will Paxil start to work?
It is considered that if you don't feel any positive benefit
after four to six weeks, then you should talk to your doctor about
trying another medication.
Generally, if Paxil is going to work for you, you will notice
some improvement in 1-2 weeks.
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Pharmacological characteristics
- Absorption: Completely absorbed via oral administration.
Food does not reduce its absorption.
- Metabolism: Paroxetine undergoes extensive first-pass
metabolism in the liver. At least 85% of a paroxetine is oxidized
to a catechol intermediate that undergoes subsequent methylation
and conjugation to clinically inactive glucuronide and sulfate
metabolites. Metabolism is accomplished in part by cytochrome
P450 2D6 (CYP2D6) ; saturation of this enzyme at clinical doses
appears to account for the nonlinear kinetics observed with
increasing dose and duration of paroxetine treatment. The elderly
may be more susceptible to the saturation of hepatic metabolic
capacity, leading to conversion to nonlinear kinetics, which
results in increased plasma concentrations of paroxetine at
lower-than-usual doses .
- Elimination half-life: 24 hours
- Excretion: Urinary excretion of unchanged paroxetine
is generally less than 2% of dose whilst that of metabolites
is about 64% of dose. About 36% of the dose is excreted in faeces,
probably via the bile, of which unchanged paroxetine represents
less than 1% of the dose. Thus paroxetine is eliminated almost
entirely by metabolism.
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Benefits
- very potent SSRI
- FDA approved for use in all five anxiety disorders
- effective for depression of all types including mild, moderate
and severe depression, and including depression comorbid with
anxiety and physical illnesses
- effective in preventing relapse or recurrence of depression
in patients treated for up to 1 year
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Concerns
- severe discontinuation syndrome and high rate of of withdrawal
reactions [1]
- highest rate of sexual side effects [2]
- potential for weight gain higher than with other SSRIs [4]
- more sedating and constipating than other SSRIs
- potential for drug interactions
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Unlabeled uses
- premature ejaculation
- chronic headache [3]
- bipolar disorder
- irritable bowel syndrome (IBS) [8]
- pathological gambling [7]
- fibromyalgia
- hot flashes [5]
- diabetic neuropathy [6]
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Mechanism of action
Paroxetine is a potent and highly selective inhibitor of neuronal
serotonin reuptake. Paroxetine inhibits the reuptake of serotonin
at the neuronal membrane, enhances serotonergic neurotransmission
by reducing turnover of the neurotransmitter, therefore it prolongs
its activity at synaptic receptor sites and potentiates 5-HT in
the CNS. Paroxetine is more potent than both sertraline and fluoxetine
in its ability to inhibit 5-HT reuptake. Paroxetine very weakly
inhibits reuptake of norepinephrine and dopamine.
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Paxil (Paroxetine) Discussion Boards & Forums
- Paxil (Paroxetine) reviews and ratings (recommended medication
by 54% of reviewers): http://psychcentral.com/meds/paxil.html
- Paxil (Paroxetine) discussion: http://www.paxilprogress.org/forums/
- Paxil, Paxil CR, Paroxetine forum: http://www.topix.net/forum/drug/paxil
- Paxil (Paroxetine) successes and progress, good stories and
bad: http://www.paxilprogress.org/forums/forumdisplay.php?s=c8e2dee0f765dbd14ceaee3328daa5bb&f=7
- Paroxetine message board: http://paroxetine.suddenlaunch2.com/
- Paxil, Seroxat, Deroxat, Paroxetine discussion: http://www.depressionforums.org/forums/index.php?showforum=57
- Paxil (Paroxetine) withdrawal:
- Paxil (Paroxetine) side effects:
- Sex and Paxil: http://www.depressionforums.org/forums/index.php?showtopic=1912
- What is the worst side effect you have suffered with this
medication? http://www.depressionforums.org/forums/index.php?showtopic=5768
- Paxil (Paroxetine) and Pregnancy
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References
- 1. Stahl MM, Lindquist M, Pettersson M, Edwards IR, Sanderson
JH, Taylor NF, Fletcher AP, Schou JS. Withdrawal reactions with
selective serotonin re-uptake inhibitors as reported to the
WHO system. Eur J Clin Pharmacol. 1997;53(3-4):163-9. PubMed
- 2. Montejo-Gonzalez AL, Llorca G, Izquierdo JA, Ledesma A,
Bousono M, Calcedo A, Carrasco JL, Ciudad J, Daniel E, De la
Gandara J, Derecho J, Franco M, Gomez MJ, Macias JA, Martin
T, Perez V, Sanchez JM, Sanchez S, Vicens E. SSRI-induced sexual
dysfunction: fluoxetine, paroxetine, sertraline, and fluvoxamine
in a prospective, multicenter, and descriptive clinical study
of 344 patients. J Sex Marital Ther. 1997 Fall;23(3):176-94.
PubMed
- 3. Foster CA, Bafaloukos J. Paroxetine in the treatment of
chronic daily headache. Headache. 1994 Nov-Dec;34(10):587-9.
PubMed
- 4. Fava M. Weight gain and antidepressants. J Clin Psychiatry.
2000;61 Suppl 11:37-41PubMed
- 5. Stearns V, Beebe KL, Iyengar M, Dube E. Paroxetine controlled
release in the treatment of menopausal hot flashes: a randomized
controlled trial. JAMA. 2003 Jun 4;289(21):2827-34. PubMed
- 6. Sindrup SH, Grodum E, Gram LF, Beck-Nielsen H. Concentration-response
relationship in paroxetine treatment of diabetic neuropathy
symptoms: a patient-blinded dose-escalation study. Ther Drug
Monit. 1991 Sep;13(5):408-14. PubMed
- 7. Kim SW, Grant JE, Adson DE, Shin YC, Zaninelli R. A double-blind
placebo-controlled study of the efficacy and safety of paroxetine
in the treatment of pathological gambling. J Clin Psychiatry.
2002 Jun;63(6):501-7. PubMed
- 8. Tabas G, Beaves M, Wang J, Friday P, Mardini H, Arnold
G. Paroxetine to treat irritable bowel syndrome not responding
to high-fiber diet: a double-blind, placebo-controlled trial.
Am J Gastroenterol. 2004 May;99(5):914-20. PubMed
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Interesting Paxil facts
- Paxil is as effective in relieving depression as TCAs such as
imipramine. However, Paxil causes fewer adverse cardiovascular and
anticholinergic effects (dry mouth, constipation, blurred vision,
urinary retention) than the older TCAs. It does not usually cause
drowsiness or low blood pressure. Paxil has no active metabolites
and leaves one's system 24 hours after it enters.
- It was the first antidepressant formally approved in the United
States for the treatment of social anxiety disorder, causing it
to be sometimes referred to (although inaccurately) as an anti-shyness
drug.
- Paxil can also be used in the treatment of premature ejaculation,
chronic headache, and bipolar disorder. Paxil has been found to
significantly reduce the symptoms of diabetic neuropathy.
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