Paroxetine: safety and tolerability issues

Paroxetine is a selective serotonin re-uptake inhibitor (SSRI) available in immediate release and controlled release (CR) formulations. Paroxetine is the most potent inhibitor of serotonin re-uptake among the now available SSRIs. Paroxetine has been approved for the treatment of major depressive disorder (MDD), obsessive-compulsive disorder, panic disorder (PD), generalised anxiety disorder, post traumatic stress disorder (PTSD), and social anxiety disorder (SAD) in adults, whereas paroxetine CR is approved for the treatment of MDD, SAD, PD and premenstrual dysphoric disorder in adults. The overall efficacy of paroxetine seems to be comparable to other SSRIs in the treatment of approved indications, although paroxetine treatment induces more sedation, constipation, sexual dysfunction, discontinuation syndrome and weight gain than other SSRIs. Recent data suggest that paroxetine treatment leads to increased rates of congenital malformations, although this evidence is not conclusive. Paroxetine and paroxetine CR are not indicated for use in the paediatric population and are categorised as Pregnancy Class D. In conclusion, whether the tolerability profile of paroxetine differs substantially from other new antidepressants (including other SSRIs) needs to be determined in adequately powered well-designed randomised controlled comparative clinical trials.     

Fluvoxamine: a selective serotonin re-uptake inhibitor for the treatment of obsessive-compulsive disorder

Fluvoxamine is the selective serotonin re-uptake inhibitor with the largest database in the treatment of obsessive-compulsive disorder, a severe, and often chronic, anxiety disorder associated with substantial impairment in functioning. The selective serotonin re-uptake inhibitors represent a first-line treatment in patients with obsessive-compulsive disorder. These agents work primarily by blocking the re-uptake of serotonin into the presynaptic nerve terminal, which is believed to be mediated by their effects on the serotonin transport system. In the last two decades, the anti-obsessional effect of fluvoxamine has been tested in several double-blind, placebo-controlled and active-comparison studies, demonstrating its superior efficacy over obsessions and compulsions compared with non-serotonergic antidepressants (i.e., desipramine) and equal efficacy to clomipramine (a tricyclic antidepressant with potent serotonin re-uptake inhibition) and other selective serotonin re-uptake inhibitors (paroxetine and citalopram). However, compared with clomipramine, the selective serotonin re-uptake inhibitor fluvoxamine showed fewer side effects and better tolerability. This reflects the poor affinity of this compound for adrenergic, muscarinic, cholinergic or histaminergic receptors.     

Paroxetine in the treatment of post-traumatic stress disorder: pooled analysis of placebo-controlled studies

Post-traumatic stress disorder (PTSD) is increasingly understood to be a medical disorder characterised by particular psychobiological dysfunctions that respond to specific treatments. Paroxetine is a selective serotonin re-uptake inhibitor that has been found effective in the treatment of major depression as well as a range of anxiety disorders. This paper reviews data on the use of paroxetine for the treatment of adult PTSD. There have been three 12-week, placebo-controlled studies of paroxetine in PTSD. As these followed a partly similar design, a pooled analysis of the studies is possible and is reported here. Paroxetine is effective in the short-term treatment of PTSD, resulting in significantly better response and remission rates than placebo, improving sleep disturbance and reducing each of the symptom clusters of PTSD, as well as the disability associated with this condition. The medication is effective in both male and female PTSD patients and whether or not there are comorbid disorders such as depression.     

Paroxetine in the treatment of post-traumatic stress disorder: pooled analysis of placebo-controlled studies

Post-traumatic stress disorder (PTSD) is increasingly understood to be a medical disorder characterised by particular psychobiological dysfunctions that respond to specific treatments. Paroxetine is a selective serotonin re-uptake inhibitor that has been found effective in the treatment of major depression as well as a range of anxiety disorders. This paper reviews data on the use of paroxetine for the treatment of adult PTSD. There have been three 12-week, placebo-controlled studies of paroxetine in PTSD. As these followed a partly similar design, a pooled analysis of the studies is possible and is reported here. Paroxetine is effective in the short-term treatment of PTSD, resulting in significantly better response and remission rates than placebo, improving sleep disturbance and reducing each of the symptom clusters of PTSD, as well as the disability associated with this condition. The medication is effective in both male and female PTSD patients and whether or not there are comorbid disorders such as depression.     

Paroxetine: safety and tolerability issues

Paroxetine is a selective serotonin re-uptake inhibitor (SSRI) available in immediate release and controlled release (CR) formulations. Paroxetine is the most potent inhibitor of serotonin re-uptake among the now available SSRIs. Paroxetine has been approved for the treatment of major depressive disorder (MDD), obsessive–compulsive disorder, panic disorder (PD), generalised anxiety disorder, post traumatic stress disorder (PTSD), and social anxiety disorder (SAD) in adults, whereas paroxetine CR is approved for the treatment of MDD, SAD, PD and premenstrual dysphoric disorder in adults. The overall efficacy of paroxetine seems to be comparable to other SSRIs in the treatment of approved indications, although paroxetine treatment induces more sedation, constipation, sexual dysfunction, discontinuation syndrome and weight gain than other SSRIs. Recent data suggest that paroxetine treatment leads to increased rates of congenital malformations, although this evidence is not conclusive. Paroxetine and paroxetine CR are not indicated for use in the paediatric population and are categorised as Pregnancy Class D. In conclusion, whether the tolerability profile of paroxetine differs substantially from other new antidepressants (including other SSRIs) needs to be determined in adequately powered well-designed randomised controlled comparative clinical trials.     

The role of cytochrome P4502D6 in the metabolism of paroxetine by human liver microsomes.

Paroxetine is a selective serotonin reuptake inhibitor possessing anti-depressant activity. Demethylenation of the methylenedioxy phenyl group is the initial step in its metabolism, the liberated carbon appearing in vitro as formate. A radioassay involving [14C-methylenedioxy] paroxetine was developed and used to examine the role of cytochrome P4502D6 in paroxetine metabolism by human liver microsomes. The rate of formate production was much higher in microsomes from an extensive metaboliser of debrisoquine than from a poor metaboliser. Also, demethylenation of paroxetine was inhibited by the quinidine and quinine isomer pair in microsomes from the extensive metaboliser only. These observations strongly suggested that the process was catalysed by the enzyme cytochrome P4502D6. Metabolism could not be completely inhibited by quinidine, the residual activity representing the contribution of at least one other enzyme. The ability of microsomes from a poor metaboliser of debrisoquine to demethylenate paroxetine provided further evidence for the involvement of an enzyme distinct from P4502D6. This was confirmed by kinetic analysis of the process in microsomes from both poor and extensive metabolisers. It is concluded that, in man, the initial step of paroxetine metabolism is performed by at least two enzymes, one of which is cytochrome P4502D6.     

Fluvoxamine: a selective serotonin re-uptake inhibitor for the treatment of obsessive-compulsive disorder

Fluvoxamine is the selective serotonin re-uptake inhibitor with the largest database in the treatment of obsessive-compulsive disorder, a severe, and often chronic, anxiety disorder associated with substantial impairment in functioning. The selective serotonin re-uptake inhibitors represent a first-line treatment in patients with obsessive-compulsive disorder. These agents work primarily by blocking the re-uptake of serotonin into the presynaptic nerve terminal, which is believed to be mediated by their effects on the serotonin transport system. In the last two decades, the anti-obsessional effect of fluvoxamine has been tested in several double-blind, placebo-controlled and active-comparison studies, demonstrating its superior efficacy over obsessions and compulsions compared with non-serotonergic antidepressants (i.e., desipramine) and equal efficacy to clomipramine (a tricyclic antidepressant with potent serotonin re-uptake inhibition) and other selective serotonin re-uptake inhibitors (paroxetine and citalopram). However, compared with clomipramine, the selective serotonin re-uptake inhibitor fluvoxamine showed fewer side effects and better tolerability. This reflects the poor affinity of this compound for adrenergic, muscarinic, cholinergic or histaminergic receptors.     

Review of sertraline and its clinical applications in psychiatric disorders

Sertraline (Zoloft, Pfizer) has been shown in numerous controlled studies to have similar efficacy to other selective serotonin (5-HT) re-uptake inhibitors (SSRIs) in the treatment of depression and anxiety disorders. Further research is indicating that the efficacy of sertraline extends even beyond the treatment of depression and anxiety to include utility in eating disorders, premenstrual dysphoric disorder (PMDD) and possibly substance abuse treatment. Along with other SSRIs, sertraline offers several advantages over older antidepressants, including improved patient tolerability, low risk of lethality in overdose and no dependence potential. In head-to-head comparisons, sertraline appears to be at least as well-tolerated as other SSRIs and may even have a more favourable side effect profile. Low potential for pharmacokinetic drug interactions is another advantage of sertraline. Unlike fluoxetine, fluvoxamine and paroxetine, sertraline is not a potent inhibitor of any of the cytochrome P450 isoenzyme systems. As a result of its proven efficacy, good tolerability and lack of pharmacokinetic interactions, sertraline should be considered first-line in the treatment of anxiety and depressive disorders.     

Paroxetine in the treatment of generalised anxiety disorder

Paroxetine is a selective serotonin re-uptake inhibitor useful in the treatment of a wide range of psychiatric disorders. Generalised anxiety disorder (GAD) is characterised by excessive persistent anxiety and worry about a number of events and activities occurring on more days than not for at least 6 months. GAD is the most common anxiety disorder in primary care settings. Paroxetine was the second antidepressant to receive an FDA indication for the treatment of GAD. In contrast to benzodiazepines, which had been the mainstay of treatment for anxiety disorders for many years, antidepressants, such as paroxetine, are more effective for the psychic symptoms of anxiety, which include worry, tension, irritability and concentration difficulties, and carry a more tolerable and safe side effect profile.     

Clinical experience with paroxetine in social anxiety disorder

Paroxetine is a selective serotonin reuptake inhibitor (SSRI) with proven efficacy in the treatment of depression, panic disorder and obsessive-compulsive disorder. Evidence that paroxetine may be effective in social anxiety disorder (social phobia) first arose from open-label studies. More recently, three multicentre, randomized, placebo-controlled trials have been performed, each lasting 12 weeks, to assess the efficacy and tolerability of paroxetine in the treatment of social anxiety disorder, and these studies are reviewed here. The data from all three studies consistently demonstrated that paroxetine was effective in reducing both the symptoms of anxiety and the disability and impairment of social anxiety disorder. Paroxetine performed significantly better than placebo on all primary (Liebowitz Social Anxiety Scale, Clinical Global Impression) and secondary (Social Avoidance and Distress Scale, Sheehan Disability Scale) outcome measures. Adverse events were restricted to those already known to be associated with SSRIs, no serious adverse events associated with medication were experienced, and the numbers withdrawing from the studies were not significantly different in the paroxetine and control groups. Taken together, these studies confirm that paroxetine is an effective and well tolerated treatment for patients with social anxiety disorder.     

Review of sertraline and its clinical applications in psychiatric disorders

Sertraline (Zoloft^®, Pfizer) has been shown in numerous controlled studies to have similar efficacy to other selective serotonin (5-HT) re-uptake inhibitors (SSRIs) in the treatment of depression and anxiety disorders. Further research is indicating that the efficacy of sertraline extends even beyond the treatment of depression and anxiety to include utility in eating disorders, premenstrual dysphoric disorder (PMDD) and possibly substance abuse treatment. Along with other SSRIs, sertraline offers several advantages over older antidepressants, including improved patient tolerability, low risk of lethality in overdose and no dependence potential. In head-to-head comparisons, sertraline appears to be at least as well-tolerated as other SSRIs and may even have a more favourable side effect profile. Low potential for pharmacokinetic drug interactions is another advantage of sertraline. Unlike fluoxetine, fluvoxamine and paroxetine, sertraline is not a potent inhibitor of any of the cytochrome P450 isoenzyme systems. As a result of its proven efficacy, good tolerability and lack of pharmacokinetic interactions, sertraline should be considered first-line in the treatment of anxiety and depressive disorders.     

Safety of benzodiazepines in the geriatric population

Generalised anxiety disorder (GAD) significantly impacts upon quality of life and has a chronic and persistent nature. GAD requires pharmacological therapies that are well-tolerated, lessen the mitigating effects of common comorbidities and do not pose a high risk for dependency or abuse. Selective serotonin and serotonin–noradrenaline re-uptake inhibitors have become more viable treatments for GAD than the traditionally used benzodiazepines due to greater efficacy and a more tolerable adverse event profile. Among these newer-generation antidepressants, only paroxetine and venlafaxine are currently FDA-approved for the treatment of GAD. Paroxetine was approved after three double-blind, placebo-controlled studies demonstrated its superior efficacy compared to placebo for short-term treatment of GAD. Venlafaxine was approved for both short- and long-term treatment of GAD after demonstrating efficacy in 8-week and 6-month double-blind, placebo-controlled trials. For both paroxetine and venlafaxine, the safety and tolerability profiles during treatment of GAD are consistent with those demonstrated during the short- and long-term treatment of patients with major depressive disorder.     

Efficacy and tolerability of controlled-release paroxetine

Paroxetine controlled-release (CR) was developed with the objective of minimizing the occurrence and severity of selective serotonin reuptake inhibitor (SSRI)-associated adverse events, thereby improving clinical outcomes. Paroxetine CR delays the onset and controls the rate of absorption of medication. Multicenter controlled clinical trials have found lower rates of early-onset, treatment-associated nausea and lower dropout rates from adverse events in depressed patients treated with paroxetine CR compared with those treated with the conventional, immediate-release formulation. At the same time, clinical response and remission rates are favorable. Other studies have demonstrated the efficacy and tolerability of paroxetine CR in geriatric depression, panic disorder, and social anxiety disorder. The CR formulation of paroxetine appears to represent an effective pharmacokinetic approach to minimizing SSRI adverse events and thereby enhancing clinical outcomes.     

Paroxetine increases serum trimipramine concentration. A report of two cases

Paroxetine is a new antidepressant, a selective serotonin reuptake inhibitor (SSRI), which has marked inhibiting effect on microsomal cytochrome P450 enzymes in human liver. In this case report we describe two patients whose serum trimipramine and desmethyltrimipramine concentrations increased markedly when paroxetine was added to their drug therapy. We suggest that this was due to the inhibitory effect of paroxetine on the CYP 2D6-mediated metabolism of trimipramine. This interaction may be of clinical importance as both patients had side-effects, such as sedation and orthostatic hypotension, during the simultaneous administration.     

Neuropharmacology of paroxetine

Paroxetine is a potent and selective serotonin reuptake inhibitor (SSRI) with some neuropharmacologic properties unique among this class of compounds. The findings of early in vitro studies demonstrated the potency of paroxetine at inhibiting 5-HT uptake in rat synaptosomes. Paroxetine also has been shown to be a potent and selective inhibitor of the human serotonin transporter (SERT) and has recently been demonstrated to have moderate affinity for the norepinephrine transporter (NET). Because of the affinity and in vitro selectivity of this SSRI, tritiated paroxetine is now widely used as a marker for SERT in laboratory settings, and its use has advanced our understanding of neurotransmitter function in the brain and periphery. The in vivo pharmacologic properties of paroxetine are well characterized, especially following acute administration. However, the pharmacologic effects of chronically administered paroxetine remain an active area of study. Paroxetine administration in laboratory animals has been shown to be associated with decreased SERT density and function, maintenance of normal firing rates and release of 5-HT, and increased activation of postsynaptic 5-HT receptors. Using a novel ex vivo assay, we have demonstrated that paroxetine exhibits dose-related inhibition of the NET in patients treated for depression. At usual clinical doses (ie, 20 mg/d), paroxetine is a potent and selective inhibitor of the SERT; however, at higher doses (ie, 40 mg/d), paroxetine can exhibit marked NET inhibition. The application of these findings of in vivo NET inhibition by paroxetine in the treatment of mood and anxiety disorders will be informed by further clinical studies.     

Paroxetine in the treatment of generalised anxiety disorder

Paroxetine is a selective serotonin re-uptake inhibitor useful in the treatment of a wide range of psychiatric disorders. Generalised anxiety disorder (GAD) is characterised by excessive persistent anxiety and worry about a number of events and activities occurring on more days than not for at least 6 months. GAD is the most common anxiety disorder in primary care settings. Paroxetine was the second antidepressant to receive an FDA indication for the treatment of GAD. In contrast to benzodiazepines, which had been the mainstay of treatment for anxiety disorders for many years, antidepressants, such as paroxetine, are more effective for the psychic symptoms of anxiety, which include worry, tension, irritability and concentration difficulties, and carry a more tolerable and safe side effect profile.     

Paroxetine: new indication. In social phobia: minimal assessment

Social phobia is generally defined as an intense and persistent fear of one or several social situations, with important repercussions for occupational activity or social life. Cognitive psychotherapy and antidepressants have partial efficacy. There is no reference drug therapy. In France, paroxetine is the first drug to be granted a licence for patients with social phobia. Clinical evaluation consists of data from four placebo-controlled trials lasting only 12 to 24 weeks. Treatment with paroxetine was associated with a significant improvement in standard social-phobia scores, although most patients remained symptomatic. Paroxetine is the best assessed selective serotonin reuptake inhibitor in this setting. However, long-term data are lacking, and the disorder is chronic. Paroxetine has not been compared with cognitive therapy. About one-third of patients in clinical trials stopped taking paroxetine, mainly because of adverse events. Gastrointestinal upset, sleep disturbance and ejaculatory problems are frequent. Paroxetine also has the potential to interact with other drugs. In practice, paroxetine may help some patients, provided they are aware of its limitations. The long-term effects of paroxetine in this setting remain unknown.     

The safety of SSRIs in generalised anxiety disorder: any reason to be anxious?

Generalised anxiety disorder (GAD) significantly impacts upon quality of life and has a chronic and persistent nature. GAD requires pharmacological therapies that are well-tolerated, lessen the mitigating effects of common comorbidities and do not pose a high risk for dependency or abuse. Selective serotonin and serotonin-noradrenaline re-uptake inhibitors have become more viable treatments for GAD than the traditionally used benzodiazepines due to greater efficacy and a more tolerable adverse event profile. Among these newer-generation antidepressants, only paroxetine and venlafaxine are currently FDA-approved for the treatment of GAD. Paroxetine was approved after three double-blind, placebo-controlled studies demonstrated its superior efficacy compared to placebo for short-term treatment of GAD. Venlafaxine was approved for both short- and long-term treatment of GAD after demonstrating efficacy in 8-week and 6-month double-blind, placebo-controlled trials. For both paroxetine and venlafaxine, the safety and tolerability profiles during treatment of GAD are consistent with those demonstrated during the short- and long-term treatment of patients with major depressive disorder.     

Setting New Standards for the Pharmacological Treatment of Panic Disorder

Three drugs are currently licensed for the treatment of panic disorder: the benzodiazepine, alprazolam; the tricyclic antidepressant, clomipramine; and, most recently, the selective serotonin reuptake inhibitor, paroxetine. Alprazolam and clomipramine are effective in the treatment of panic disorder, but are less than ideal agents due to their tolerability profiles. An extensive clinical trial programme has been undertaken to investigate the efficacy and tolerability of paroxetine treatment in panic disorder. This article reviews the clinical evidence for the short- and long-term efficacy and tolerability of paroxetine in panic disorder, and its effect on relapse prevention and on quality of life. The results from the short-term studies indicate that paroxetine is effective in treating panic disorder (with or without agoraphobia) either alone or in combination with cognitive-behavioural therapy. The minimum effective dose is 40 mg daily. Paroxetine was equally as effective as clomipramine in reducing the frequency of panic attacks but produced an earlier improvement in symptomatology. Continued treatment with paroxetine over periods of up to 9 months provided evidence that paroxetine maintained its anti-panic effect and prevented relapse. Paroxetine was well-tolerated during both the short- and long-term studies at doses of up to 60 mg per day. © 1997 John Wiley & Sons, Ltd.     

The use of escitalopram beyond major depression: pharmacological aspects, efficacy and tolerability in anxiety disorders

Escitalopram, the active (S)-enantiomer of citalopram, has been approved in many countries throughout the world for the treatment of depression and anxiety disorders. It is more potent and selective than citalopram in inhibiting serotonin re-uptake in the CNS, and less potent than various other selective serotonin re-uptake inhibitors in relation to other transporter proteins and receptors: in particular, it is six times less potent than citalopram in binding to the histamine H1 and muscarinic receptors. Escitalopram has favourable pharmacokinetics: it is rapidly absorbed, has a bioavailability of 80% and is not affected by food intake. It has little potential for drug interactions: it has low protein binding and, as it is metabolised by three CYP isozymes, any impairment in the activity of one is unlikely to have a significant effect on metabolic clearance. Caution is necessary only when it is coadministered with drugs metabolised by CYP2D6, such as metoprolol, or administered to the elderly or patients with severe hepatic or renal impairment. The multiple-dose pharmacokinetics of oral escitalopram are proportional at a range of doses including its therapeutic doses. Escitalopram is approved for the treatment of a number of anxiety disorders. It seems to be well tolerated and induces few or no discontinuation symptoms, and may be considered a first-line agent for the pharmacotherapy of obsessive-compulsive disorder, generalised anxiety disorder, panic disorder and social phobia. Further studies are needed to define its activity in impulse control disorders.