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Trade names | Paxil, Seroxat, Loxamine |
AHFS/Drugs.com | Monograph |
MedlinePlus | a698032 |
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Routes of administration | Oral (By mouth) |
Drug class | Selective serotonin reuptake inhibitor (SSRI) |
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Bioavailability | Extensively absorbed from the GI tract, but extensive first-pass metabolism in the liver [3] [4] [5] [6] |
Protein binding | 93–95% [3] [4] [5] |
Metabolism | Extensive, hepatic (mostly CYP2D6-mediated) [3] [4] [5] |
Elimination half-life | 21 hours [3] [4] [5] |
Excretion | Renal (64%; 2% unchanged and 62% as metabolites), faecal (36%; <1% unchanged) [3] [4] [5] |
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ECHA InfoCard | 100.112.096 |
Chemical and physical data | |
Formula | C19H20FNO3 |
Molar mass | 329.371 g·mol−1 |
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Paroxetine, sold under the brand names Paxil and Seroxat among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. [7] It is used to treat major depressive disorder, obsessive-compulsive disorder, panic disorder, social anxiety disorder, post-traumatic stress disorder, generalized anxiety disorder, and premenstrual dysphoric disorder. [7] It has also been used in the treatment of premature ejaculation and hot flashes due to menopause. [7] [8] It is taken orally (by mouth). [7]
Common side effects include drowsiness, dry mouth, loss of appetite, sweating, trouble sleeping, and sexual dysfunction. [7] Serious side effects may include suicidal thoughts in those under the age of 25, serotonin syndrome, and mania. [7] While the rate of side effects appears similar compared to other SSRIs and SNRIs, antidepressant discontinuation syndromes may occur more often. [9] [10] Use in pregnancy is not recommended, while use during breastfeeding is relatively safe. [11] It is believed to work by blocking the reuptake of the chemical serotonin by neurons in the brain. [7]
Paroxetine was approved for medical use in the United States in 1992 and initially sold by GlaxoSmithKline. [7] [12] It is on the World Health Organization's List of Essential Medicines. [13] It is available as a generic medication. [14] In 2020, it was the 82nd most commonly prescribed medication in the United States, with more than 9 million prescriptions. [15] [16] In 2018, it was in the top 10 of most prescribed antidepressants in the United States. [17] In 2012, the United States Department of Justice fined GlaxoSmithKline $3 billion for withholding data, unlawfully promoting use in those under 18, and preparing an article that misleadingly reported the effects of paroxetine in adolescents with depression following its clinical trial study 329. [18] [19] [20]
Paroxetine is primarily used to treat major depressive disorder, obsessive-compulsive disorder, post-traumatic stress disorder, social anxiety disorder, and panic disorder. It is also occasionally used for agoraphobia, generalized anxiety disorder, premenstrual dysphoric disorder, and menopausal hot flashes. [21] [22] [23] [24] [25]
A variety of meta-analyses have been conducted to evaluate the efficacy of paroxetine in depression. They have variously concluded that paroxetine is superior or equivalent to placebo and that it is equivalent to other antidepressants. [26] [27] [28] Despite this, there was no clear evidence that paroxetine was better or worse compared with other antidepressants at increasing response to treatment at any point in time. [29]
Paroxetine was the first antidepressant approved in the United States for the treatment of panic disorder. [30] [ page needed ] Several studies have concluded that paroxetine is superior to placebo in the treatment of panic disorder. [28] [31]
Paroxetine has demonstrated efficacy for the treatment of social anxiety disorder in adults and children. [32] [33] It is also beneficial for people with co-occurring social anxiety disorder and alcohol use disorder. [34] It appears to be similar to a number of other SSRIs. [35]
Paroxetine is used in the treatment of obsessive-compulsive disorder. [36] Comparative efficacy of paroxetine is equivalent to that of clomipramine and venlafaxine. [37] [38] Paroxetine is also effective for children with obsessive-compulsive disorder. [39]
Paroxetine is approved for treatment of PTSD in the United States, Japan, and Europe. [40] [41] [42] In the United States, it is approved for short-term use. [41]
Paroxetine is also FDA-approved for generalized anxiety disorder. [43]
In 2013, low-dose paroxetine was approved in the US for the treatment of moderate-to-severe vasomotor symptoms such as hot flashes and night sweats associated with menopause. [8] At the low dose used for menopausal hot flashes, side effects are similar to placebo and dose tapering is not required for discontinuation. [44]
Studies have also shown paroxetine "appears to be well-tolerated and improve the overall symptomatology in patients with fibromyalgia", but is less robust in helping with the pain involved. [45] [46]
Common side effects include drowsiness, dry mouth, loss of appetite, sweating, insomnia, and sexual dysfunction. [7] Serious side effects may include suicide in those under the age of 25, serotonin syndrome, and mania. [7] While the rate of side effects appears similar compared to other SSRIs and SNRIs, antidepressant discontinuation syndromes may occur more often. [9] [10] Use in pregnancy is not recommended, while use during breastfeeding is relatively safe. [11]
Paroxetine shares many of the common adverse effects of SSRIs, including (with the corresponding rates seen in people treated with placebo in parentheses):
Most of these adverse effects are transient and go away with continued treatment. Central and peripheral 5-HT3 receptor stimulation is believed to result in the gastrointestinal effects observed with SSRI treatment. [47] Compared to other SSRIs, it has a lower incidence of diarrhea, but a higher incidence of anticholinergic effects (e.g., dry mouth, constipation, blurred vision, etc.), sedation/somnolence/drowsiness, sexual side effects, and weight gain. [48]
Due to reports of adverse withdrawal reactions upon terminating treatment, the Committee for Medicinal Products for Human Use at the European Medicines Agency recommends gradually reducing over several weeks or months if the decision to withdraw is made. [49] See also Discontinuation syndrome (withdrawal).
Mania or hypomania may occur in 1% of patients with depression and up to 12% of patients with bipolar disorder. [50] This side effect can occur in individuals with no history of mania, but it may be more likely to occur in those with bipolar disorder or with a family history of mania. [51]
Like other antidepressants, paroxetine may increase the risk of suicidal thinking and behaviour in people under the age of 25. [52] [53] The FDA conducted a statistical analysis of paroxetine clinical trials in children and adolescents in 2004 and found an increase in suicidality and ideation as compared to placebo, which was observed in trials for both depression and anxiety disorders. [54] In 2015 a paper published in The BMJ that reanalysed the original case notes argued that in Study 329, [55] assessing paroxetine and imipramine against placebo in adolescents with depression, the incidence of suicidal behavior had been under-reported and the efficacy exaggerated for paroxetine. [56] [57] [58] [59] [60]
Sexual dysfunction, including loss of libido, anorgasmia, lack of vaginal lubrication, and erectile dysfunction, is one of the most commonly encountered adverse effects of treatment with paroxetine and other SSRIs. While early clinical trials suggested a relatively low rate of sexual dysfunction, more recent studies in which the investigator actively inquires about sexual problems suggest that the incidence is higher than 70%. [61] Symptoms of sexual dysfunction have been reported to persist after discontinuing SSRIs, although this is thought to be occasional. [62] [63] [64]
Antidepressant exposure (including paroxetine) is associated with shorter duration of pregnancy (by three days), increased risk of preterm delivery (by 55%), lower birth weight (by 75 g or 2.6 oz), and lower Apgar scores (by <0.4 points). [65] [66] The American College of Obstetricians and Gynecologists recommends that for pregnant women and women planning to become pregnant, paroxetine "be avoided, if possible", as it may be associated with increased risk of birth defects. [67] [68]
Babies born to women who used paroxetine during the first trimester have an increased risk of cardiovascular malformations, primarily ventricular and atrial septal defects. Unless the benefits of paroxetine justify continuing treatment, consideration should be given to stopping or switching to another antidepressant. [69] Paroxetine use during pregnancy is associated with about 1.5– to 1.7-fold increase in congenital birth defects, in particular, heart defects, cleft lip and palate, clubbed feet, or any birth defects. [70] [71] [72] [73] [74]
Many psychoactive medications can cause withdrawal symptoms upon discontinuation from administration. Paroxetine has among the highest incidence rates and severity of withdrawal syndrome of any medication of its class. [75] Common withdrawal symptoms for paroxetine include nausea, dizziness, lightheadedness and vertigo; insomnia, nightmares and vivid dreams; feelings of electricity in the body, as well as rebound depression and anxiety. Liquid formulation of paroxetine is available and allows a very gradual decrease of the dose, which may prevent discontinuation syndrome. Another recommendation is to temporarily switch to fluoxetine, which has a longer half-life and thus decreases the severity of discontinuation syndrome. [76] [77] [78]
In 2002, the U.S. FDA published a warning regarding "severe" discontinuation symptoms among those terminating paroxetine treatment, including paraesthesia, nightmares, and dizziness. The agency also warned of case reports describing agitation, sweating, and nausea. In connection with a Glaxo spokesperson's statement that withdrawal reactions occur only in 0.2% of patients and are "mild and short-lived", the International Federation of Pharmaceutical Manufacturers Associations said GSK had breached two of the federation's codes of practice. [79]
Paroxetine prescribing information posted at GlaxoSmithKline has been updated related to the occurrence of a discontinuation syndrome, including serious discontinuation symptoms. [69]
Acute overdosage is often manifested by emesis, lethargy, ataxia, tachycardia, and seizures. Plasma, serum, or blood concentrations of paroxetine may be measured to monitor therapeutic administration, confirm a diagnosis of poisoning in hospitalized patients or to aid in the medicolegal investigation of fatalities. Plasma paroxetine concentrations are generally in a range of 40–400 μg/L in persons receiving daily therapeutic doses and 200–2,000 μg/L in poisoned patients. Postmortem blood levels have ranged from 1–4 mg/L in acute lethal overdose situations. [80] [81] Along with the other SSRIs, sertraline and fluoxetine, paroxetine is considered a low-risk drug in cases of overdose. [82]
Interactions with other drugs acting on the serotonin system or impairing the metabolism of serotonin may increase the risk of serotonin syndrome or neuroleptic malignant syndrome (NMS)-like reaction. Such reactions have been observed with SNRIs and SSRIs alone, but particularly with concurrent use of triptans, MAO inhibitors, antipsychotics, or other dopamine antagonists.
The prescribing information states that paroxetine should "not be used in combination with an MAOI (including linezolid, an antibiotic which is a reversible non-selective MAOI), or within 14 days of discontinuing treatment with an MAOI", and should not be used in combination with pimozide, thioridazine, tryptophan, or warfarin. [69]
Paroxetine interacts with the following cytochrome P450 enzymes: [48] [83]
Paroxetine has been shown to be an inhibitor of G protein-coupled receptor kinase 2 (GRK2). [84] [85]
Paroxetine is the most potent and one of the most specific selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors (SSRIs). [87] It also binds to the allosteric site of the serotonin transporter, similarly to escitalopram, though less potently so. [88] Paroxetine also inhibits the reuptake of norepinephrine to a lesser extent (<50 nmol/L). [89] Based on evidence from four weeks of administration in rats, the equivalent of 20 mg paroxetine taken once daily occupies approximately 88% of serotonin transporters in the prefrontal cortex. [83]
Receptor | Ki (nM) |
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SERT | 0.07 – 0.2 |
NET | 40 – 85 |
DAT | 490 |
D2 | 7,700 |
5-HT1A | 21,200 |
5-HT2A | 6,300 |
5-HT2C | 9,000 |
α1 | 1,000 – 2,700 |
α2 | 3,900 |
M1 | 72 |
H1 | 13,700 – 23,700 |
Paroxetine is well-absorbed following oral administration. [83] It has an absolute bioavailability of about 50%, with evidence of a saturable first pass effect. [93] When taken orally, it achieves maximum concentration in about 6–10 hours [83] and reaches steady-state in 7–14 days. [93] Paroxetine exhibits significant interindividual variations in volume of distribution and clearance. [93] Less than 2% of an oral dose is excreted in urine unchanged. [93]
Paroxetine is a mechanism-based inhibitor of CYP2D6. [86] [94]
Paroxetine was approved for medical use in the United States in 1992 and initially sold by GlaxoSmithKline. [7] [95] It is currently available as a generic medication. [14] In 2017, it was the 68th most commonly prescribed medication in the United States, with more than eleven million prescriptions. [15] [16]
GlaxoSmithKline has paid substantial fines, paid settlements in class-action lawsuits, and become the subject of several highly critical books about its marketing of paroxetine, in particular the off-label marketing of paroxetine for children, the suppression of negative research results relating to its use in children, and allegations that it failed to warn consumers of substantial withdrawal effects associated with use of the drug. [18] [19]
In early 2004, GSK agreed to settle charges of consumer fraud for $2.5 million. [96] The legal discovery process also uncovered evidence of deliberate, systematic suppression of unfavorable Paxil research results. One of GSK's internal documents read, "It would be commercially unacceptable to include a statement that efficacy [in children] had not been demonstrated, as this would undermine the profile of paroxetine". [97]
The United States Department of Justice fined GlaxoSmithKline $3 billion in 2012, for withholding data, unlawfully promoting use in those under 18, and preparing an article that misleadingly reported the effects of paroxetine in adolescents with depression following its clinical trial study 329. [18] [19] [20]
On 12 February 2016, the UK Competition and Markets Authority imposed record fines of £45 million on companies which were found to have infringed European Union and UK Competition law by entering into agreements to delay the market entry of generic versions of the drug in the UK. GlaxoSmithKline received the bulk of the fines, being fined £37,600,757. Other companies, which produce generics, were issued fines which collectively total £7,384,146. UK public health services are likely to claim damages for being overcharged in the period where the generic versions of the drug were illegally blocked from the market, as the generics are over 70% less expensive. GlaxoSmithKline may also face actions from other generics manufacturers who incurred loss as a result of the anticompetitive conduct. [98] On 18 April 2016, appeals were lodged with the Competition Appeal Tribunal by the companies which were fined. [99] [100] [101] [102] [103]
GSK marketed paroxetine through television advertisements throughout the late 1990s and early 2000s. Commercials also aired for the CR version of the drug beginning in 2003. [104]
In 2007, paroxetine was ranked 94th on the list of bestselling drugs, with over $1 billion in sales. In 2006, paroxetine was the fifth-most prescribed antidepressant in the U.S. retail market, with more than 19.7 million prescriptions. [105] In 2007, sales had dropped slightly to 18.1 million but paroxetine remained the fifth-most prescribed antidepressant in the U.S. [106] [107]
Trade names include Aropax, Paretin, Brisdelle, Deroxat, Paxil, [108] [109] Pexeva, Paxtine, Paxetin, Paroxat, Paraxyl, [110] Sereupin, Daparox and Seroxat.
Several studies have suggested that paroxetine can be used in the treatment of premature ejaculation. In particular, intravaginal ejaculation latency time (IELT) was found to increase with 6- to 13-fold, which was somewhat longer than the delay achieved by the treatment with other SSRIs (fluvoxamine, fluoxetine, sertraline, and citalopram). [111] [112] [113] However, paroxetine taken acutely ("on demand") 3–10 hours before coitus resulted only in a "clinically irrelevant and sexually unsatisfactory" 1.5-fold delay of ejaculation and was inferior to clomipramine, which induced a fourfold delay. [113]
There is also evidence that paroxetine may be effective in the treatment of compulsive gambling [114] and hot flashes. [115]
Benefits of paroxetine prescription for diabetic neuropathy [116] or chronic tension headache [117] are uncertain.
Although the evidence is conflicting, paroxetine may be effective for the treatment of dysthymia, a chronic disorder involving depressive symptoms for most days of the year. [118]
There is evidence to support that paroxetine selectively binds to and inhibits G protein-coupled receptor kinase 2 (GRK2) in mice with heart failure. Since GRK2 regulates the activity of the beta adrenergic receptor, which becomes desensitized in cases of heart failure, paroxetine (or a paroxetine derivative) could be used as a heart failure treatment in the future. [84] [85] [119]
Paroxetine has been identified as a potential disease-modifying osteoarthritis drug. [120]
Paroxetine is a common finding in waste water. [121] It is highly toxic to the alga Pseudokirchneriella subcapitata (syn. Raphidocelis subcapitata ). [121]
It also is toxic to the soil nematode Caenorhabditis elegans . [122]
Alberca et al., 2016 finds paroxetine acts as a trypanocide against T. cruzi . [123]
Alberca et al., 2016 finds a leishmanicide effect. [124] Alberca finds that paroxetine produces cell death of the promastigotes of L. infantum . [124] The mechanism of action remains unknown. [124]
Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction.
An anxiolytic is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxiety disorders and their related psychological and physical symptoms.
Sertraline, sold under the brand name Zoloft among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. The efficacy of sertraline for depression is similar to that of other antidepressants, and the differences are mostly confined to side effects. Sertraline is better tolerated than the older tricyclic antidepressants. Sertraline is effective for panic disorder, social anxiety disorder, generalized anxiety disorder (GAD), and obsessive–compulsive disorder (OCD). However, for OCD, cognitive behavioral therapy, particularly in combination with sertraline, is a better treatment. Although approved for post-traumatic stress disorder (PTSD), sertraline leads to only modest improvement in this condition. Sertraline also alleviates the symptoms of premenstrual dysphoric disorder (PMDD) and can be used in sub-therapeutic doses or intermittently for its treatment.
Escitalopram, sold under the brand names Lexapro and Cipralex, among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. Escitalopram is mainly used to treat major depressive disorder and generalized anxiety disorder. It is taken by mouth, available commercially as an oxalate salt exclusively.
Citalopram, sold under the brand name Celexa among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used to treat major depressive disorder, obsessive compulsive disorder, panic disorder, and social phobia. The antidepressant effects may take one to four weeks to occur. It is typically taken orally. In some European countries, it is sometimes given intravenously to initiate treatment, before switching to the oral route of administration for continuation of treatment. It has also been used intravenously in other parts of the world in some other circumstances.
Fluvoxamine, commonly sold under the brand names Luvox and Faverin, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is primarily used to treat major depressive disorder and obsessive–compulsive disorder (OCD), but is also used to treat anxiety disorders such as panic disorder, social anxiety disorder, and post-traumatic stress disorder.
Tranylcypromine, sold under the brand name Parnate among others, is a monoamine oxidase inhibitor (MAOI). More specifically, tranylcypromine acts as nonselective and irreversible inhibitor of the enzyme monoamine oxidase (MAO). It is used as an antidepressant and anxiolytic agent in the clinical treatment of mood and anxiety disorders, respectively.
Venlafaxine, sold under the brand name Effexor among others, is an antidepressant medication of the serotonin-norepinephrine reuptake inhibitor (SNRI) class. It is used to treat major depressive disorder, generalized anxiety disorder, panic disorder, and social anxiety disorder. Studies have shown that Venlafaxine improves quality of life. It may also be used for chronic pain. It is taken by mouth. It is also available as the salt venlafaxine besylate in an extended-release formulation.
Duloxetine, sold under the brand name Cymbalta among others, is a medication used to treat major depressive disorder, generalized anxiety disorder, fibromyalgia, neuropathic pain and central sensitization. It is taken by mouth.
Serotonin–norepinephrine reuptake inhibitors (SNRIs) are a class of antidepressant medications used to treat major depressive disorder (MDD), anxiety disorders, obsessive–compulsive disorder (OCD), social phobia, attention-deficit hyperactivity disorder (ADHD), chronic neuropathic pain, fibromyalgia syndrome (FMS), and menopausal symptoms. SNRIs are monoamine reuptake inhibitors; specifically, they inhibit the reuptake of serotonin and norepinephrine. These neurotransmitters are thought to play an important role in mood regulation. SNRIs can be contrasted with the selective serotonin reuptake inhibitors (SSRIs) and norepinephrine reuptake inhibitors (NRIs), which act upon single neurotransmitters.
Azapirones are a class of drugs used as anxiolytics, antidepressants, and antipsychotics. They are commonly used as add-ons to other antidepressants, such as selective serotonin reuptake inhibitors (SSRIs).
Milnacipran is a serotonin–norepinephrine reuptake inhibitor (SNRI) used in the clinical treatment of fibromyalgia. It is not approved for the clinical treatment of major depressive disorder in the US, but it is in other countries.
Fluoxetine, sold under the brand name Prozac, among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used for the treatment of major depressive disorder, obsessive–compulsive disorder (OCD), anxiety, bulimia nervosa, panic disorder, and premenstrual dysphoric disorder. It is also approved for treatment of major depressive disorder in adolescents and children 8 years of age and over. It has also been used to treat premature ejaculation. Fluoxetine is taken by mouth.
A serotonin reuptake inhibitor (SRI) is a type of drug which acts as a reuptake inhibitor of the neurotransmitter serotonin by blocking the action of the serotonin transporter (SERT). This in turn leads to increased extracellular concentrations of serotonin and, therefore, an increase in serotonergic neurotransmission. It is a type of monoamine reuptake inhibitor (MRI); other types of MRIs include dopamine reuptake inhibitors and norepinephrine reuptake inhibitors.
The number of new psychiatric drugs, and especially antidepressants on the market in Japan, is significantly less than Western countries.
Vilazodone, sold under the brand name Viibryd among others, is a medication used to treat major depressive disorder. It is classified as a serotonin modulator and is taken by mouth.
Vortioxetine, sold under the brand names Trintellix and Brintellix among others, is a medication used to treat major depressive disorder. Its effectiveness is viewed as similar to that of other antidepressants. It is taken by mouth.
Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions.
Selective serotonin reuptake inhibitors, or serotonin-specific re-uptake inhibitor (SSRIs), are a class of chemical compounds that have contributed to the major advances as antidepressants where they have revolutionised the treatment of depression and other psychiatric disorders. The SSRIs are therapeutically useful in the treatment of panic disorder (PD), posttraumatic stress disorder (PTSD), social anxiety disorder, obsessive-compulsive disorder (OCD), premenstrual dysphoric disorder (PMDD), and anorexia. There is also clinical evidence of SSRIs efficiency in the treatment of the negative symptoms of schizophrenia and their ability to prevent cardiovascular diseases.
Study 329 was a clinical trial which was conducted in North America from 1994 to 1998 to study the efficacy of paroxetine, an SSRI anti-depressant, in treating 12- to 18-year-olds diagnosed with major depressive disorder. Led by Martin Keller, then professor of psychiatry at Brown University, and funded by the British pharmaceutical company SmithKline Beecham—known since 2000 as GlaxoSmithKline (GSK)—the study compared paroxetine with imipramine, a tricyclic antidepressant, and placebo. SmithKline Beecham had released paroxetine in 1991, marketing it as Paxil in North America and Seroxat in the UK. The drug attracted sales of $11.7 billion in the United States alone from 1997 to 2006, including $2.12 billion in 2002, the year before it lost its patent.
The United States alleges that, among other things, GSK participated in preparing, publishing and distributing a misleading medical journal article that misreported that a clinical trial of Paxil demonstrated efficacy in the treatment of depression in patients under age 18, when the study failed to demonstrate efficacy.
There were no significant differences between the three SSRIs that had been tested in placebo-controlled studies: paroxetine; sertraline; fluvoxamine.