Platelet 5-hydroxytryptamine is decreased in a preliminary group of depressed patients receiving the 5-hydroxytryptamine re-uptake inhibiting drug fluoxetine

Association between selective serotonin reuptake inhibitor and risk of peripheral artery disease in diabetes mellitus: Propensity score matching and landmark analysis

An increasing number of studies have demonstrated the bidirectional hemostatic effect of selective serotonin reuptake inhibitors (SSRIs) on the risk of cerebrovascular and cardiovascular diseases. However, no previous study has focused on the relationship between SSRI and the risk of peripheral artery disease (PAD) in diabetes mellitus (DM). We sought to evaluate the association between SSRIs and the PAD risk in individuals with DM.We conducted a retrospective, population-based cohort study using data from the Longitudinal Health Insurance Database from 1999 to 2010 in Taiwan. A total of 5049 DM patients were included and divided into 2 groups: DM with SSRI users and DM with SSRI non-users. Propensity score matching and 1-year landmark analysis were used for our study design. Stratified Cox proportional hazard regressions were used to analyze the hazard ratio of the PAD risk in certain subgroups.DM with SSRI users did not affect the PAD risk compared to DM with SSRI non-users. These findings were consistent with all sensitivity analyses (i.e., age, sex, SSRI doses, antithrombotic medication use, and medical and psychiatric comorbidities).In this study, we found that there was no significant difference of PAD risk between DM with SSRI users and DM with SSRI non-users. DM with SSRI user did not affect PAD risk across any SSRI dose, age, sex, antithrombotic medications, and multiple comorbidities in the subgroup analysis.

Autocrine and paracrine regulatory functions of platelet serotonin

Platelets serotonin (5-hydroxytrytamine, 5-HT) uptake and storage in dense granules is tightly regulated by the serotonergic transport system in the blood. Several 5-HT transporters (5-HTTs) have been identified in the vasculature and blood cells, beyond them 5-HTT is the major 5-HT transporter in platelets. Abnormal 5-HT concentrations in the blood plasma or increased platelet 5-HT uptake or abnormal release contribute to the development of various diseases in the vasculature. Consequently, several clinical trials suggested the positive therapeutic effects of 5-HTT blockade in the circulation. Inhibition of 5-HT strongly attenuates autocrine and paracrine functions of platelets, influencing platelet aggregation, vascular contraction, permeability, tissue repair, wound healing, immunity and cancer. Here, we highlight the current state of basic biological research regarding the hemostatic and non-hemostatic functions of platelet-derived 5-HT in normal and disease conditions. We also describe the physiological consequences of targeting platelet 5-HT functions in thrombosis, stroke, inflammation and cancer to overcome common health problems.

Coagulation activation and fibrinolysis impairment are reduced in patients with anxiety and depression when medicated with serotonergic antidepressants

AIMS

Anxiety disorders have been shown to be correlated with an activation of coagulation and impairment of fibrinolysis. The aim of the study was to assess whether medication with a serotonergic antidepressant, which has been associated with abnormal bleeding, may modify this effect.

METHODS

Thirty-one anxiety patients, mostly with comorbid depression, and 31 healthy controls were included in the study. Group differences between anxiety patients medicated with a serotonergic antidepressant, patients without serotonergic antidepressant and controls were assessed for activated partial thromboplastin time, fibrinogen, factor VII, factor VIII, von Willebrand factor, von Willebrand ristocetin cofactor activity, prothrombin fragment 1 + 2, thrombin-antithrombin complex, d-dimer, α2-antiplasmin, plasmin-α2-antiplasmin complex (PAP), tissue plasminogen activator and plasminogen activator inhibitor. Intervening variables, such as age, sex, body mass index and smoking, were accounted for.

RESULTS

We found lower coagulation measures for fibrinogen (P = 0.03) and plasminogen activator inhibitor (P = 0.01), and higher levels of PAP (P = 0.046) in patients with serotonergic antidepressant than in patients without serotonergic antidepressant. When controlling for smoking and body mass index, differences between the two groups were significant for PAP (P = 0.02), von Willebrand ristocetin cofactor activity (P = 0.02) and activated partial thromboplastin time (P = 0.046). Coagulation scores were similar in patients with serotonergic antidepressant to those of healthy controls.

CONCLUSIONS

Serotonergic antidepressants may counteract a procoagulant effect of anxiety and/or depression in anxiety patients.

Citalopram intervention for hostility: results of a randomized clinical trial

Hostility is associated with an increased risk for cardiovascular disease (CVD). Because central serotonin may modulate aggression, we might expect selective serotonin reuptake inhibitors (SSRIs) to be effective in reducing hostility. Such effects have never been examined in individuals scoring high on hostility who are otherwise free from major Axis I psychopathology according to criteria in the Diagnostic and Statistical Manual of Mental Disorders (4th ed., Text Revision; American Psychiatric Association, 2000). A total of 159 participants (ages 30?50 years, 50% female) scoring high on 2 measures of hostility and with no current major Axis I diagnosis were randomly assigned to 2 months of citalopram (40 mg, fixed-flexible dose) or placebo. Adherence was assessed by electronic measurement and by drug exposure assessment. Treated participants showed larger reductions in state anger (Condition x Time; p = .01), hostile affect (p = 02), and, among women only, physical and verbal aggression (p = .005) relative to placebo controls. Treatment was also associated with relative increases in perceived social support (p = .04). The findings have implications for understanding the central nervous system correlates of hostility, its associations with other psychosocial risk factors for CVD, and, potentially, the design of effective interventions.

Serotonin (5-HT) transporter ligands affect plasma 5-HT in rats

Dual dopamine (DA)/serotonin (5-HT)-releasing agents are promising candidate medications for stimulant addiction and other disorders. However, certain 5-HT transporter (SERT) substrates are associated with development of idiopathic pulmonary arterial hypertension (IPAH) and valvular heart disease (VHD). According to the "5-HT hypothesis," SERT substrates increase the risk for developing IPAH and VHD by increasing plasma 5-HT. To test this hypothesis directly, we determined the effects of acute and chronic fenfluramine, and other SERT ligands, on plasma 5-HT in male rats. For acute treatments, rats received i.v. vehicle or test drug (0.3 and 1.0 mg/kg), and serial blood samples were withdrawn. For chronic treatments, vehicle or test drug was infused via osmotic minipump (3 and 10 mg/kg/d) for 2 weeks. On the last day of infusion, rats received i.v. fenfluramine challenge (1 mg/kg), and serial blood samples were withdrawn. Plasma 5-HT was measured using ex vivo microdialysis in whole-blood samples. Baseline plasma 5-HT was <1.0 nM. Acute injection of fenfluramine or other SERT substrates caused large (up to 24-fold) dose-dependent increases in plasma 5-HT. Chronic fenfluramine at 3 and 10 mg/kg/d produced 1.7- and 3.5-fold increases in baseline plasma 5-HT, while chronic fluoxetine had no effect. Chronic infusions of fenfluramine or fluoxetine diminished the ability of acute fenfluramine to elevate dialysate 5-HT, and both drugs markedly reduced whole-blood 5-HT. Acute fenfluramine increases plasma 5-HT to concentrations that are below the micromolar levels necessary to produce adverse cardiovascular effects. Chronic fenfluramine and fluoxetine have minimal effects on plasma 5-HT, suggesting that the increased risk for IPAH associated with fenfluramine does not depend upon elevations in plasma 5-HT.

Effect of selective serotonin reuptake inhibitors on platelet activation: can they prevent acute myocardial infarction?

In recent years a large body of evidence from several longitudinal studies has emerged suggesting that depression is an independent risk factor for cardiovascular disease (CVD) and that the association between depression and increased CVD risk is not merely due to negative mood-driven behavior related with depression. Even though the underlying mechanisms are not well understood, several hypotheses and explanations have been proposed such as increased activation of the hypothalamic-pituitary-adrenal axis, abnormalities in the sympathoadrenal system, or abnormalities in platelet function. Platelet function abnormalities, including increased platelet reactivity, may predispose patients with depressive disorders to clotting diatheses and may explain their vulnerability to CVD. Serotonin secreted by platelets induces both platelet aggregation and coronary vasoconstriction. Even though serotonin itself is only a weak platelet agonist, it markedly enhances platelet reactions to a variety of other agonists. Several studies have shown that selective serotonin reuptake inhibitors (SSRIs) reduce platelet and whole blood serotonin concentrations after repeated doses, and could therefore exert an inhibitory effect on platelet activation. For that reason, it was hypothesized that SSRIs could have a protective effect against myocardial infarction (MI). Results from three currently available epidemiological studies assessing the risk of MI in patients treated with antidepressants, including SSRIs, are controversial with respect to a potential beneficial effect of SSRIs on CVD risk in depressed patients. However, there is evidence that exposure to SSRIs does not substantially increase the risk of CVD in patients. A recent randomized, double-blind, placebo-controlled, multicenter trial that evaluated the safety and efficacy of the SSRI sertraline in patients with major depression and acute MI or unstable angina suggested that sertraline is well tolerated and effective. Further epidemiological studies or longer-term clinical trials may shed more light on this issue, and answer the question conclusively, whether the effect of SSRIs on platelets or another mechanism translates into a decreased risk of CVD in depressed patients.

Clinical evidence for serotonin and norepinephrine reuptake inhibition of duloxetine

Most antidepressants in clinical use are believed to function by enhancing neurotransmission of serotonin [5-hydroxytryptamine (5-HT)] and/or norepinephrine (NE) via inhibition of neurotransmitter reuptake. Agents that affect reuptake of both 5-HT and NE (serotonin-norepinephrine reuptake inhibitors) have been postulated to offer greater efficacy for the treatment of major depressive disorder (MDD). These dual-acting agents also display a broader spectrum of action, including efficacy for MDD and associated painful physical symptoms, diabetic peripheral neuropathic pain, generalized anxiety disorder, and fibromyalgia syndrome. Substantial preclinical evidence shows that duloxetine, an approved drug for the treatment of MDD, generalized anxiety disorder, and the management of diabetic peripheral neuropathic pain, inhibits reuptake of both 5-HT and NE. This paper reviews clinical and neurochemical evidence of duloxetine's effects on 5-HT and NE reuptake inhibition. The clinical evidence supporting duloxetine's effects on NE reuptake inhibition includes indirect measures such as altered excretion of NE metabolites, cardiovascular effects, and treatment-emergent adverse event profiles similar to those for other drugs believed to act through the inhibition of NE reuptake. In summary, the data presented in this report provide clinical evidence of a mechanism for duloxetine involving both 5-HT and NE reuptake inhibition in humans and are consistent with preclinical evidence for 5-HT/NE reuptake inhibition.

Influence of antidepressants on hemostasis

Antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs), are widely used for the treatment of depression and anxious disorders. The observation that depression is an independent risk factor for cardiovascular mortality and morbidity in patients with ischemic heart disease, the assessment of the central role of serotonin in pathophysiological mechanisms of depression, and reports of cases of abnormal bleeding associated with antidepressant therapy have led to investigations of the influence of antidepressants on hemostasis markers. In this review, we summarize data regarding modifications of these markers, drawn from clinical studies and case reports. We observed an association between the type of antidepressant drug and the number of abnormal bleeding case reports, with or without modifications of hemostasis markers. Drugs with the highest degree of serotonin reuptake inhibition - fluoxetine, paroxetine, and sertraline - are more frequently associated with abnormal bleeding and modifications of hemostasis markers. The most frequent hemostatic abnormalities are decreased platelet aggregability and activity, and prolongation of bleeding time. Patients with a history of coagulation disorders, especially suspected or documented thrombocytopenia or platelet disorder, should be monitored in case of prescription of any serotonin reuptake inhibitor (SRI). Platelet dysfunction, coagulation disorder, and von Willebrand disease should be sought in any case of abnormal bleeding occurring during treatment with an SRI. Also, a non-SSRI antidepressant should be favored over an SSRI or an SRI in such a context. Considering the difficulty in performing platelet aggregation tests, which are the most sensitive in SRI-associated bleeding, and the low sensitivity of hemostasis tests when performed in case of uncomplicated bleeding in the general population, establishing guidelines for the assessment of SRI-associated bleeding complications remains a challenge.

Platelets and anti-platelet therapy

Platelets play a central role in the hemostatic process and consequently are similarly involved in the pathological counterpart, thrombosis. They adhere to various subendothelial proteins, exposed either by injury or disease, and subsequently become activated by the thrombogenic surface or locally produced agonists. These activated platelets aggregate to form a platelet plug, release agonists which recruit more platelets to the growing thrombus, and provide a catalytic surface for thrombin generation and fibrin formation. These platelet-rich thrombi are responsible for the acute occlusion of stenotic vessels and ischemic injury to heart and brain. A range of anti-platelet drugs are currently used, both prophylactically and therapeutically, in regimens to manage thrombo-embolic disorders. These include inhibitors of the generation, or effects, of locally produced agonists; several large clinical trials have supported roles for cyclooxygenase inhibitors, which prevent thromboxane generation, and thienopyridine derivatives, which antagonize ADP receptors. Similarly intravenous alpha IIb beta 3 antagonists have been shown to be effective anti-thrombotics, albeit in highly selective situations; in contrast, to date studies with their oral counterparts have been disappointing. Recent advances in understanding of platelet physiology have suggested several novel, if yet untested, targets for anti-platelet therapy. These include the thrombin receptor, the serotonin handling system, and the leptin receptor.

Venous thromboembolism and escitalopram

Selective serotonin reuptake inhibitors (SSRIs) are currently used as a first-line treatment for depression, as they have a favorable side-effect profile. Escitalopram, a new SSRI, is also well-tolerated and serious side effects are rarely associated with its use. There have been several reports that SSRIs might increase bleeding tendency in some patients by affecting platelet function. However, to our knowledge, there have been no reports about their relation to thrombosis. In this brief report, we present a case of venous thromboembolism associated with escitalopram in a patient with psychotic depression without any major risk factors for thrombosis. SSRIs might have a dual effect on platelet function. The immediate and early effect of SSRI use on platelets might be an increase be an in tendency for thrombosis, whereas the late effect after repeated dosing might be an increase in tendency to bleed, as suggested by previous literature.

Analgesic effect of amitriptyline in chronic tension-type headache is not directly related to serotonin reuptake inhibition

The tricyclic antidepressant amitriptyline is the only documented and most widely used prophylactic drug for chronic tension-type headache (CTTH). However, it is not fully clarified whether the serotonin (5-HT) reuptake inhibition plays a major role for the analgesic effect of amitriptyline. To explore the importance of 5-HT reuptake inhibition for mechanism of action of the analgesic effect of amitriptyline we investigated platelet 5-HT levels during preventive treatment of CTTH with amitriptyline, the selective serotonin reuptake inhibitor citalopram, and placebo. Thirty-four patients with CTTH were given preventive treatment with amitriptyline 75 mg/day, the selective 5-HT reuptake inhibitor citalopram 20 mg/day, and placebo in a 32-week, double-blind, placebo-controlled, three-way crossover trial. Blood samples were collected in the last week of each treatment period. Platelet 5-HT was used as a measure of 5-HT reuptake inhibition and determined by high performance liquid chromatography. Area under the headache curve was 308 (157-715) (median with quartiles in parentheses) with amitriptyline and significantly lower than 377 (158-1121) with citalopram (P = 0.04) and 441 (178-1408) with placebo (P = 0.002). There was no difference between citalopram and placebo (P = 0.23). Platelet 5-HT was 0.4 (0.3-0.7) x 10(-18)mol/platelet with citalopram, which was significantly lower than 1.7 (1.2-2.4) x 10(-18)mol/platelet with amitriptyline (P < 0.001), and 3.5 (2.8-4.3) x 10(-18)mol/platelet with placebo (P < 0.001). The lower platelet 5-HT during treatment with citalopram than amitriptyline indicates that 5-HT reuptake was most effectively inhibited by citalopram. In contrast, amitriptyline was most effective in reduction of headache. This suggests that the analgesic effect of amitriptyline in CTTH is not solely due to 5-HT reuptake inhibition and that other mechanisms such as norepinephrine reuptake inhibition, NMDA receptor antagonism, blockade of muscarinic receptors and ion channels should be addressed in the future research.

Serotonin and fluoxetine levels in plasma and platelets after fluoxetine treatment in depressive patients

Depression is a mood disorder characterized by complex alterations of neurotransmitters such as serotonin, norepinephrine, and dopamine. In particular, there is substantial evidence of abnormalities in serotonin neurotransmission. Peripheral parameters of serotoninergic transmission, such as the 5-hydroxytryptamine content of plasma and platelets, have been used to identify biochemical alterations related to depression. In recent years, these parameters have also been used to examine the mechanism of action of antidepressive drugs such as the selective serotonin reuptake inhibitors. This study investigated the interaction between the plasma and platelet levels of fluoxetine and serotonin after fluoxetine administration to depressed patients. Twelve patients affected by major depression (according to the DSM-IV criteria) received a single oral dose of fluoxetine in the morning: 5 mg in the first 5 days, 10 mg from day 6 to day 10, and 20 mg from day 11 to day 40. Blood samples were collected at 0, 7, 10, and 24 hours after drug administration on the day 1 of fluoxetine 5 mg and on the 1st and the 30th day of fluoxetine 20 mg (days 11 and 40 of treatment, respectively). Plasma fluoxetine and serotonin levels increased after drug administration, reaching the highest levels on the 30th day of fluoxetine 20 mg. Fluoxetine levels were also detectable in platelets, with a time variation similar to plasma values. Platelet serotonin levels decreased after drug administration, and the lowest values were observed on the 30th day of fluoxetine 20 mg.

Use of selective serotonin reuptake inhibitors and risk of developing first-time acute myocardial infarction

AIMS

Selective serotonin reuptake inhibitors (SSRIs) have been associated with serotonin depletion in platelets, potentially leading to abnormal aggregation and prolonged bleeding time. In view of the importance of serotonin in coronary thrombosis, and decreased platelet serotonin concentrations associated with SSRIs, the present study was performed to test the hypothesis of a decreased risk of acute myocardial infarction (AMI) associated with SSRIs.

METHODS

We conducted a population-based case-control analysis using the UK General Practice Research Database (GPRD). A total of 3319 patients aged 75 years or younger free of clinical conditions predisposing to ischaemic heart disease, with a first-time diagnosis of AMI between 1992 and 1997, and 13 139 controls without AMI matched to cases for age, sex, general practice attended, and calendar time were included. Conditional logistic regression was used to estimate relative risks.

RESULTS

Adjusted odds ratios (with 95% CI) for current use of SSRIs, non-SSRIs, or other antidepressants, compared to the group of nonusers of antidepressants were 0.9 (95% CI 0.5,1.8), 0.9 (95% CI 0.7,1.2), and 1.3 (95% CI 0.6,2.8), respectively. As compared with nonuse of SSRIs, current use (regardless of any other antidepressants used) resulted in an adjusted OR of 1.1 (95% CI 0.7,1.6).

CONCLUSIONS

The current analysis provides evidence that SSRI exposure does not substantially decrease the risk of developing first-time AMI in patients free of factors predisposing to ischaemic heart disease. However, due to relatively small numbers of exposed subjects and the resulting wide confidence intervals, further studies may be needed to document a lack of effect of SSRIs in subjects without pre-existing diseases predisposing to AMI.

[Hemorrhagic syndromes related to selective serotonin reuptake inhibitor (SSRI) antidepressants. Seven case reports and review of the literature]

PURPOSE

Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed. Since their release unexpected adverse effects such as bleeding disorders have been described.

METHODS

Thirty patients with either hematoma or muco-cutaneous bleeding have been selected from case reports of the Saint-Etienne Pharmacovigilance center and from a literature review.

RESULTS

The female/male sex-ratio was 3:4 and the mean age 42 years. Two newborns who had been exposed in utero to SSRIs were also included in the study. Eleven patients presented an underlying disease or were at risk. Various adverse effects such as bruising, hematoma, petechiae or purpura, epistaxis, and more rarely intestinal hemorrhage, ocular bleeding or cerebral hemorrhage were encountered. Symptoms were sometimes associated with prolonged bleeding time and platelet aggregation disorders and usually resolved within two days to four months after treatment discontinuation.

CONCLUSION

Hematoma and muco-cutaneous bleeding would therefore be related to treatment, including selective serotonin reuptake inhibitors. However, these adverse effects are still poorly known and rarely reported. The main mechanism suggested would be a decrease in serotonin platelet leading to a defect in platelet aggregation. However, an increase in capillary fragility or susceptibility related to the patient's condition might be involved. Study of hemostasis history in patients requiring treatment with SSRIs might be of value.

The acute effects of dexfenfluramine on human and porcine pulmonary vascular tone and resistance

STUDY OBJECTIVES

Treatment with anorectics has become an important aspect of care for the severely obese. One such anorectic, the phenylethylamine dexfenfluramine (dFen), has been associated with the development of pulmonary hypertension. It works by reducing the neuronal uptake of 5-hydroxytryptamine (5-HT; serotonin) through inhibition of the 5-HT transporter. In this study we investigated whether dFen has a direct vasoconstrictor action on human and porcine pulmonary vasculature.

DESIGN

For the human study, tissue was obtained from patients who had undergone lung and heart-lung transplantation. The effect of dFen was studied in seven isolated colloid perfused human lungs and in rings of human pulmonary artery (PA) dissected from the lungs of a further 19 patients. For the porcine study, regional pulmonary vascular resistances (PVRs) were measured in isolated perfused porcine lungs. Vasoconstriction was assessed following dFen alone and in combination with hypoxia, cyclo-oxygenase blockade (indomethacin, 10(-5) mol/L), or nitric oxide synthase (NOS) blockade (N(G)-nitro-L-arginine, 10(-5) mol/L).

RESULTS

In the human study, 5-HT and dFen caused only limited increases in tension of isolated rings of PA. The concentration of dFen, 10(-4) mol/L, that was needed to increase tension was higher than that found normally in treated patients where peak levels are 3. 3 x 10(-7) mol/L. Other vasoconstrictors such as prostaglandin F(2)alpha, 10(-5) mol/L, and the thromboxane analog U46619, 10(-6) mol/L, produced far greater increases in tension. Ketanserin, 10(-4) mol/L, attenuated the constrictor response to 5-HT but had no effect on the constrictor response to dFen. Removal of the endothelium did not influence the response to dFen. In the isolated ventilated and perfused lungs, dFen caused an increase in PVR again only at a comparatively high concentration, 10(-4) mol/L. In the porcine study, dFen, 10(-4) mol/L, did not increase any PVR during normoxia or following NOS blockade. Small insignificant increases in PVR occurred during hypoxia and after cyclo-oxygenase blockade.

CONCLUSION

These results do not support the view that dFen would act as a direct vasoconstrictor when given in the usual doses. However, delayed elimination of dFen could raise tissue concentrations to high levels and give rise to vasoconstriction and pulmonary hypertension.

Is phentermine an inhibitor of monoamine oxidase? A critical appraisal

Phentermine produces a spectrum of concentration-dependent biochemical effects. It interacts with NE transporters at 0.1 microM, DA transporters at about 1 microM, 5-HT transporters at 15 microM and MAO-A at about 100 microM. When administered at typical anorectic doses, phentermine primarily interacts with DA and NE transporters and does not produce biochemical or neurochemical effects which would occur if it were inhibiting MAO-A. Some other explanation other than MAO inhibition must be sought to explain how oral phentermine increases platelet 5-HT, since platelet MAO-B does not metabolize platelet 5-HT, and since amphetamine-type drugs are even weaker inhibitors of MAO-B than MAO-A. Clinical studies in humans have shown that amphetamine, which is a more potent inhibitor of MAO-A than phentermine, does not inhibit MAO-A at therapeutic doses. Neither phentermine alone, fluoxetine alone or their combined use have been associated with cardiac valvulopathy, and clinical experience has shown their combined use to be free of significant adverse effects. Viewed collectively, there appears to be no data to support the hypothesis that phentermine inhibits MAO at typical therapeutic doses.

Fluoxetine tenth anniversary update: the progress continues

This tenth anniversary review/update of fluoxetine concentrates on the past 5 years of its clinical application. The mechanism of action of fluoxetine; its metabolism; its efficacy in patients with various diagnostic subgroups of depression, patients with coincident medical disease, children and adolescents with depression, patients with eating disorders, and patients with obsessive-compulsive disorder (OCD); its long-term (maintenance) efficacy; its side effects and toxicity; and pharmacoeconomic considerations are reviewed. Pharmacotherapy is currently the only proven method for treating major depressive disorder that is applicable to all levels of severity of major depressive illness. Since its introduction 10 years ago, fluoxetine has been available to psychiatrists, primary care physicians, and other nonpsychiatric physicians as full-dose effective pharmacotherapy for patients with depression. Fluoxetine has been widely prescribed by physicians knowledgeable in pharmacology and in the treatment of depression because of its proven efficacy (ie, equal to that of tricyclic antidepressants [TCAs]), its ease of administration (with full therapeutic dosing usually starting from day 1), its generally benign side-effect profile, its remarkable safety in over-dose, and its proven effectiveness in the most common depressed patient population--anxious, agitated, depressed patients--as well as in patients with various subtypes and severities of depression. In more recent years it has also proved effective in the treatment of bulimia, an entity for which only limited or inadequate treatment options had been previously available. In OCD, fluoxetine, with its more acceptable side-effect profile and greater ease of dosing, presents a favorable alternative to previous drug therapy and is useful in treating both obsessions and compulsions. Fluoxetine is currently recognized among clinicians as efficacious in treating anxiety disorders and is being used successfully in special depressed populations such as patients with medical comorbidity, elderly patients, adolescents, and children. Rapid discontinuation or missed doses of short-half-life selective serotonin reuptake inhibitors, TCAs, and heterocyclic antidepressants are associated with withdrawal symptoms of a somatic and psychological nature, which cannot only be disruptive, but can also be suggestive of relapse or recurrence of depression. In striking contrast to these short-half-life antidepressants, fluoxetine is rarely associated with such sequelae on sudden discontinuation or missed doses. This preventive effect against withdrawal symptoms on discontinuation of fluoxetine is attributed to the unique extended half-life of this antidepressant. Current studies show that the overall increased effectiveness of fluoxetine in treating depression compensates for its higher cost, compared with older drugs, by reducing the need for physician contact because of increased compliance and less need of titration, and by reducing premature patient discontinuation, thereby yielding fewer relapses, less recurrence, and less reutilization of mental health services.