Pharmacokinetics of selective serotonin reuptake inhibitors

Neonatal treatment with fluoxetine reduces depressive behavior induced by forced swim in adult rats

Serotonin plays a role at the pathophysiology of depression in humans and in experimental models. The present study investigated the depressive behavior and the weigh evolution in adult rats (60 days) treated from the 1st to the 21st postnatal day with fluoxetine, a selective serotonin reuptake inhibitor (10 mg/kg, sc, daily). The depressive behavior was induced by the forced swim test (FST). The animals were submitted to two sessions of FST: 1st session for 15 min and the 2nd session 24h later, for 5 min. During the 2nd session the Latency of the Attempt of Escape (LAE) and Behavioral Immobility (BI) were appraised. The Fluoxetine group when compared to the Control group, showed an increase in LAE and a decrease in BI. The neonatal administration of fluoxetine reduced the depressive behavior in adult rats, possibly by increase in the brain serotonergic activity. This alteration can be associated to process of neuroadaptation.

High-performance liquid chromatography-mass spectrometry method for the determination of paroxetine in human plasma

A rapid and specific liquid chromatographic mass spectrometric (LC-MS-MS) method has been developed for the determination of paroxetine in human plasma. The procedure involves a liquid-liquid extraction of paroxetine and fluoxetine (internal standard) with cyclohexane-ethyl acetate. The standard curve was linear over a working range of 0.2-50 ng/ml. The lower limit of quantitation was 0.2 ng/ml. No endogenous compounds were found to interfere with the analysis. The absolute recovery was 70.8% for paroxetine and 84.1% for the internal standard. The accuracy of inter-assay and intra-assay accuracy was in the ranges -4.8 to -0.5% and -3.4 to 4.8%, respectively. This method proved to be suitable for bioequivalence studies by being simple, selective and reproducible.

Comparison of the anticholinergic effects of the serotonergic antidepressants, paroxetine, fluvoxamine and clomipramine

Paroxetine, a selective serotonin reuptake inhibitor, shows relatively high affinity for muscarinic acetylcholine receptors compared to other selective serotonin reuptake inhibitors. To determine whether paroxetine has anticholinergic effects in vivo, we examined the effects of paroxetine on oxotremorine-induced tremor, spontaneous defecation and passive avoidance performance using mice and compared the results with those using fluvoxamine, another selective serotonin reuptake inhibitor, and clomipramine, a tricyclic antidepressant with serotonin selectivity. The potency of antidepressant activity as determined in the tail suspension test was paroxetine>fluvoxamine>clomipramine. Paroxetine and clomipramine inhibited oxotremorine-induced tremor, reduced spontaneous defecation and impaired passive avoidance performance, while fluvoxamine did not have similar effects. A comparison of ED(50) values showed that the ratio of anticholinergic effect to antidepressant activity was fluvoxamine, >3.2; paroxetine, 2.1-2.6; clomipramine, <0.8. These results suggest that paroxetine may induce fewer adverse anticholinergic effects than clomipramine, but more than fluvoxamine.

Fluvoxamine augmentation of olanzapine in chronic schizophrenia: pharmacokinetic interactions and clinical effects

Olanzapine is a substrate of the cytochrome P450 enzyme (CYP) 1A2. In this study, pharmacokinetic interactions and clinical effects of adding the CYP1A2 inhibitor fluvoxamine to steady-state olanzapine was examined in patients suffering from schizophrenia. Eight patients had been treated for at least 3 months with 10 to 20 mg/day olanzapine. Fluvoxamine (100 mg/day) was added (week 0) to the olanzapine treatment and continued for 8 weeks. Concentrations of olanzapine and its metabolite N-desmethylolanzapine and of fluvoxamine were analyzed at weeks 0, 1, 4, and 8. Addition of fluvoxamine resulted in a 12% to 112% ( < 0.01) increase of olanzapine from 31 +/- SD 15 ng/mL (week 0) to 56 +/- 31 ng/mL (week 8) in all patients. N-desmethylolanzapine concentrations were not significantly changed ( > 0.05). Fluvoxamine concentrations were 48 +/- 26 ng/mL on week 1 and 83 +/- 47 ng/mL on week 8. It is concluded that fluvoxamine affects olanzapine degradation and thus increases olanzapine concentrations. Although the combination was well tolerated in this sample and the negative symptom response appeared to be favorable in at least five patients, the combination therapy of olanzapine and fluvoxamine should be used cautiously and should be controlled by therapeutic drug monitoring to avoid olanzapine-induced side effects or intoxications.

Serotonin clearance in vivo is altered to a greater extent by antidepressant-induced downregulation of the serotonin transporter than by acute blockade of this transporter

Serotonin uptake, mediated by the serotonin transporter (SERT), is blocked acutely by antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), but such blockade does not correlate temporally with the onset of therapeutic improvement. Treatment with SSRIs for 21 d induced downregulation of the SERT (Benmansour et al., 1999). The time course of SERT downregulation as well as the time course for its recovery after cessation of treatment with the SSRI sertraline were investigated using tritiated cyanoimipramine to measure SERT binding sites. To determine if there was a temporal correlation between the time when sertraline induced downregulation of the SERT and when marked alteration in SERT function occurred, clearance of locally applied 5-HT into the CA3 region of hippocampus was achieved using in vivo electrochemistry. After 4 or 10 d treatment with sertraline, SERT binding sites decreased very little (15-30%), and the chronoamperometric signals for serotonin in sertraline-treated rats were comparable with ones obtained in control animals. By contrast, after 15 d of treatment, when SERT binding sites were markedly reduced by 80%, there was robust decrease in the clearance of 5-HT. Moreover, the functional consequences of SERT downregulation as measured by chronoamperometry were significantly greater than those seen after acute blockade of the SERT by SSRIs. SERT binding sites decreases are not a consequence of reduced SERT gene expression, as revealed by in situ hybridization measurements. SSRI-induced downregulation of the SERT may be a key component for the clinical response to SSRIs.

Transplacental transfer of citalopram, fluoxetine and their primary demethylated metabolites in isolated perfused human placenta

OBJECTIVE

To investigate the transplacental transfer and the effects of protein binding on the transfer of citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine in the isolated perfused human placenta model.

DESIGN

Prospective observational study.

METHODS

Fifteen term human placentas were obtained immediately after delivery with maternal consent and a 2-hour non-recirculating perfusion cycle of a single placental cotyledon was set up. Citalopram (1230 nmol/L) and desmethylcitalopram (600 nmol/L) or fluoxetine (1455 nmol/L) and desmethylfluoxetine (1525 nmol/L) were added to the maternal reservoir and their appearance to the fetal circulation was followed by repeated measurements. To investigate the effect of protein binding on the transfer of citalopram and fluoxetine, nine additional perfusions were performed without albumin in the perfusion medium. Citalopram and desmethylcitalopram concentrations were measured by reversed-phase high performance liquid chromatography. Fluoxetine and desmethylfluoxetine concentrations was measured by gas chromatography and antipyrine (used as a reference compound) concentrations spectrophotometrically.

RESULTS

The mean (SD) steady-state transplacental transfer (TPT(SS)%) for citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine was 9.1%, 5.6% (P = 0.017 compared with citalopram), 8.7% and 9.1%, respectively, calculated as the ratio between the steady-state concentrations in fetal venous and maternal arterial sides. The TPT(SS)%s of citalopram, desmethylcitalopram, fluoxetine and desmethylfluoxetine were 86%, 50%, 88% and 91% of that of freely diffusable antipyrine. The absence of albumin significantly reduced the transfer of citalopram and fluoxetine (TPT(SS)% 1.1% and 4.8%, respectively) but not the transfer of antipyrine.

CONCLUSION

Citalopram, fluoxetine and desmethylfluoxetine all cross the human placenta, and may, therefore, affect the perinatal outcome of infants exposed to these drugs during pregnancy. The transfer of desmethylcitalopram was significantly lower, which in the clinical setting may suggest lower fetal exposure of serotonin re-uptake inhibition by citalopram compared with fluoxetine. The presence of albumin was necessary for the transplacental transfer of both citalopram and fluoxetine.

Potentiation of DOM-induced stimulus control by fluoxetine and citalopram: role of pharmacokinetics

The present investigation examined the interaction between 2,5-dimethoxy-4-methylamphetamine [DOM] and the selective serotonin reuptake inhibitor [SSRI] citalopram in rats trained with DOM [0.6 mg/kg; 75 min pretreatment time] as a discriminative stimulus. Pretreatment with citalopram at a dose of 1.0 mg/kg shifted the DOM dose response relationship to the left. Unlike previously tested SSRI's, the enhancement of DOM-induced stimulus control occurred in the absence of significant partial substitution by citalopram. DOM brain levels were measured using a GC-MS method both in the presence and absence of citalopram and fluoxetine in order to evaluate the pharmacokinetic contribution to the observed behavioral effect. The data indicated that fluoxetine but not citalopram significantly increased DOM brain levels. It is concluded that the effects of DOM as a discriminative stimulus are potentiated by the acute administration of citalopram and this effect is not mediated by additivity or pharmacokinetic mechanisms.

Review of fluoxetine and its clinical applications in premenstrual dysphoric disorder

The largest number of antidepressant treatment trials in premenstrual syndrome and premenstrual dysphoric disorder (PMDD) have been conducted with fluoxetine. Fluoxetine and other selective serotonin re-uptake inhibitors (SSRIs) clearly reduce premenstrual emotional and physical symptoms and improve premenstrual psychosocial functioning. Fluoxetine was the first SSRI to be approved by the FDA as a treatment for the emotional and physical symptoms of PMDD. Fluoxetine 20 mg has been reported to be effective for emotional and physical premenstrual symptoms with continuous daily dosing (every day of the menstrual cycle) and with luteal phase daily dosing (from ovulation to menses). In addition, premenstrual emotional symptoms have been reported to improve with fluoxetine 10 mg in luteal phase daily dosing and with 90 mg 2 and 1 weeks prior to menses. Fluoxetine is generally a well-tolerated treatment for PMDD and discontinuation effects have not been reported with intermittent dosing regimens.

Rapid and sensitive determination of sertraline in human plasma using gas chromatography-mass spectrometry

A method for the determination of sertraline in human plasma using gas chromatography-mass spectrometry (GC-MS), with the selected ion-monitoring (SIM) mode, was described. The following was used in this study: (1) single liquid-liquid extraction at alkaline pH after deproteinization of plasma protein and (2) perfluoroacylation with HFBA, which has higher sensitivity (about 10-fold) compared with previous reported derivatization. The detection limit for the SIM of sertraline as an N-HFB derivative was 0.1 ng/ml, and its recovery was 80-85%. The linear response was obtained in the range of 0.2-10.0 ng/ml with a correlation coefficient of 0.999. The coefficient of variation (C.V.%) was less than 12.1% in the 1-30 ng/ml, and less than 18.2% at 0.2 ng/ml, and the accuracy was less than 10% at all of the concentration range. These findings indicate that this assay method has adequate precision and accuracy to determine the amount of sertraline in human plasma. After pharmacokinetics was performed with this assay method following oral administration of sertraline hydrochloride in man, moment analysis revealed that pharmacokinetic parameters for sertraline (Cmax, 10.3 ng/ml; Tmax, 8.0 h; T(1/2) 28.6 h) were similar to previously reported results. These results indicate that this simple and sensitive assay method is readily applicable to the pharmacokinetic studies of sertraline.

Sertraline and fluoxetine treatment of obsessive-compulsive disorder: results of a double-blind, 6-month treatment study

The purpose of this study was to evaluate the comparative efficacy and tolerability of sertraline and fluoxetine in the treatment of obsessive-compulsive disorder (OCD). Outpatients meeting DSM-IV criteria for OCD, with a Yale-Brown Obsessive-Compulsive (Y-BOCS) total score >or= 17, an NIMH Global Obsessive-Compulsive (NIMH-OC) scale score >or= 7, and a CGI-Severity score >or= 4 were randomized to 24 weeks of double-blind treatment with sertraline (N = 77) or fluoxetine (N = 73). Primary efficacy measures consisted of the Y-BOCS, the NIMH-OC scale, and the CGI-Severity (CGI-S) and Improvement (CGI-I) scales. Equivalent and significant (p < 0.001) improvement was found at week 24 in Y-BOCS and NIMH-OC scale scores for sertraline and fluoxetine. After 12 weeks, 49.2% of patients on sertraline were rated on the CGI-S scale as being mildly ill or not ill compared to 24.6% on fluoxetine (p < 0.01). A Cox analysis found patients on sertraline to have a statistically nonsignificant 42% greater likelihood of achieving a response by week 12 (CGI-I, much or very much improved; 95% CI, 0.85, 2.38; p = 0.18). Sertraline treatment also resulted in a higher proportion of remissions than fluoxetine (defined as a CGI-I <or= 2 and a Y-BOCS score <or= 11), both at week 12 (20% vs. 8%; chi2, 3.95; df 1; p = 0.047) and week 24 (36% vs. 22%; chi2, 3.18; df, 1; p = 0.075). Both medications were well-tolerated and demonstrated significant efficacy in the treatment of outpatients with moderate to severe OCD with the subjects treated with sertraline showing a greater likelihood of remission as well as an earlier improvement on some but not all efficacy measures

Effect of maternal fluoxetine administration on uterine blood flow, fetal blood gas status, and growth

Clinical depression, diagnosed in 5-15% of women during pregnancy, increases the risk of negative pregnancy outcomes including an increased incidence of low birth weight newborns and preterm delivery. Fluoxetine, a selective serotonin reuptake inhibitor, is often prescribed to treat depression due to its efficacy, high margin of safety, and mild side effects. However, fluoxetine initially increases plasma serotonin concentration, and serotonin causes uterine vasoconstriction in sheep, which could result in fetal hypoxemia. To assess fetal fluoxetine effects, late-gestation pregnant sheep were surgically prepared for the measurement of blood gases, heart rate, blood pressure, and uterine artery blood flow (n = 29). Ewes received a 70-mg bolus i.v. infusion of fluoxetine over 2 min in 10 mL of sterile water followed by continuous infusion at a rate of 100 microg/min for 8 d (n = 14), or continuous infusion of sterile water (n = 15). Transient decreases in uterine artery blood flow, fetal PO(2), and oxygen saturation were observed within the first 15 min after fluoxetine exposure, which did not return to normal values by 24 h. Fetal pH decreased and PCO(2) increased over the first 4 h with a return to normal by 24 h. However, there were no differences in uterine artery blood flow, blood gas status, or cardiovascular measures between the control and fluoxetine group over the rest of the 8-d infusion period. Thus, fluoxetine exposure during pregnancy has transient effects on fetal status that may be of developmental consequence if they occur repetitively.

In vitro inhibition of pimozide N-dealkylation by selective serotonin reuptake inhibitors and azithromycin

Pimozide is often coprescribed with serotonin reuptake inhibitor (SSRI) antidepressants to treat depression in patients with Tourette's syndrome. In human liver microsomes (HLMs), the inhibition of the primary route of pimozide metabolism, N-dealkylation to 1,3-dihydro-1-(4-piperidinyl)-2H-benzimidazol-2-one (DHPBI), by four SSRIs (fluoxetine, sertraline, paroxetine, and fluvoxamine) and azithromycin was tested. Inhibition constants (K(i) values) were estimated from Dixon plots (three HLMs for each inhibitor) using the appropriate enzyme inhibition model by nonlinear regression. At 10 microM paroxetine, sertraline, fluoxetine, or fluvoxamine, the formation of DHPBI from pimozide (10 microM) in HLMs was inhibited by an average (three HLMs) of 7%, 7.7%, 8%, and 16%, respectively, whereas this inhibition did not exceed 55% at the maximum concentrations (100 microM) of the SSRIs tested. Azithromycin had negligible effect on pimozide (10 microM) N-dealkylation (19% at 100 microM azithromycin). These inhibition data were compared with ketoconazole, which was included as a positive control of CYP3A inhibition. At 0.1 microM and 0.5 microM ketoconazole, the formation of DHPBI from 10 microM pimozide was inhibited by 32% and 62%, respectively. The K(i) values (+/- SD) of ketoconazole, sertraline, fluvoxamine, azithromycin, fluoxetine, and paroxetine were 0.07 microM, 89 +/- 44 microM, 89 +/- 24 microM, 103 +/- 52 microM, 117 +/- 27 microM, and 129 +/- 33 microM, respectively. These values are least 100-fold higher than the expected plasma concentrations after the usual daily doses of the SSRIs and azithromycin, suggesting that coadministration of SSRIs and azithromycin are unlikely to markedly diminish the elimination of pimozide in patients. However, in vivo predictions from in vitro data are not always perfect. In vivo, the SSRIs or azithromycin may concentrate in the liver relative to plasma. In addition, the possibility that these drugs could alter pimozide disposition through effects on transport proteins or via promoter repression cannot be ruled out.

Prolonged prenatal psychotropic medication exposure alters neonatal acute pain response

Selective serotonin reuptake inhibitors (SSRIs) and benzodiazepines are frequently used to treat maternal depression during pregnancy, however the effect of increased serotonin (5HT) and gamma-amino-butyric acid (GABA) agonists in the fetal human brain remains unknown. 5HT and GABA are active during fetal neurologic growth and play early roles in pain modulation, therefore, if prolonged prenatal exposure alters neurodevelopment this may become evident in altered neonatal pain responses. To examine biologic and behavioral effects of prenatal exposure, neonatal responses to acute pain (phenylketonuria heel lance) in infants with prolonged prenatal exposure were examined. Facial action (Neonatal Facial Coding System) and cardiac autonomic reactivity derived from the relationship between respiratory activity and short term variations of heart rate (HRV) were compared between 22 infants with SSRI exposure (SE) [fluoxetine (n = 7), paroxetine (n = 11), sertraline (n = 4)]; 16 infants exposed to SSRIs and clonazepam (SE+) [paroxetine (n = 14), fluoxetine (n = 2)]; and 23 nonexposed infants during baseline, lance, and recovery periods of a heel lance. Length of maternal SSRI use did not vary significantly between exposure groups-[mean (range)] SE:SE+ 183 (31-281):141 (54-282) d (p > 0.05). Infants exposed to SE and SE+ displayed significantly less facial activity to heel lance than control infants. Mean HR increased with lance, but was significantly lower in SE infants during recovery. Using measures of HRV and the transfer relationship between heart rate and respiration, SSRI infants had a greater return of parasympathetic cardiac modulation in the recovery period, whereas a sustained sympathetic response continued in the control group. Prolonged prenatal SSRI exposure appears to be associated with reduced behavioral pain responses and increased parasympathetic cardiac modulation in recovery following an acute neonatal noxious event. Possible 5HT-mediated pain inhibition, pharmacologic factors and the developmental course remain to be studied.

Summary of information on human CYP enzymes: human P450 metabolism data

This chapter is an update of the data on substrates, reactions, inducers, and inhibitors of human CYP enzymes published previously by Rendic and DiCarlo (1), now covering selection of the literature through 2001 in the reference section. The data are presented in a tabular form (Table 1) to provide a framework for predicting and interpreting the new P450 metabolic data. The data are formatted in an Excel format as most suitable for off-line searching and management of the Web-database. The data are presented as stated by the author(s) and in the case when several references are cited the data are presented according to the latest published information. The searchable database is available either as an Excel file (for information contact the author), or as a Web-searchable database (Human P450 Metabolism Database, www.gentest.com) enabling the readers easy and quick approach to the latest updates on human CYP metabolic reactions.

Prevalence and patterns of concomitant use of selective serotonin reuptake inhibitors and other antidepressants in a high-cost polypharmacy cohort

BACKGROUND

Concomitant antidepressant therapy for patients who do not respond to selective serotonin reuptake inhibitors (SSRIs) may be appropriate under close medical supervision. However, little is known about the prevalence or patterns of concurrent antidepressant therapy in a typical large health maintenance organization.

OBJECTIVE

The purpose of this study was to determine the prevalence of concomitant SSRI-antidepressant therapy and to assess the relationship between concomitant SSRI therapy, patient demographic characteristics, and the use of multiple prescribers and pharmacies.

METHODS

This was a retrospective analysis of administrative prescription and medical claims data from January 1998 through September 1999. Data were obtained on beneficiaries who had >15 prescriptions dispensed in either of the first 2 quarters of 1999 and/or patients who accrued >$1,000 in prescription costs in either or both of the quarters. Patients were defined as undergoing concomitant SSRI therapy if they had received > or = 14 days of concomitant treatment with 2 SSRIs, an SSRI and tricyclic antidepressant, an SSRI and benzodiazepine, or an SSRI and miscellaneous antidepressant. Contingency analysis and logistic regression were used to identify factors associated with concomitant SSRI therapy.

RESULTS

The relative risk for concomitant SSRI-SSRI therapy for patients with multiple prescribers versus a single prescriber was 2.32; the relative risk for patients receiving prescriptions from multiple pharmacies versus a single pharmacy was 2.97. Female patients were 19.8% more likely than male patients to receive concomitant SSRI therapy. Use of multiple prescribers increased the odds for concomitant SSRI therapy by >3.0 across the 4 therapeutic combinations. Use of multiple pharmacies increased the odds for concomitant SSRI-SSRI therapy by 5.42.

CONCLUSIONS

Prescription of concomitant SSRI therapy was strongly associated with changes in strength of dosage and products and with use of multiple prescribers and pharmacies.

O-Dealkylation of fluoxetine in relation to CYP2C19 gene dose and involvement of CYP3A4 in human liver microsomes

This work evaluated the kinetic behavior of fluoxetine O-dealkylation in human liver microsomes from different CYP2C19 genotypes and identified the isoenzymes of cytochrome P450 involved in this metabolic pathway. The kinetics of the rho-trifluoromethylphenol (TFMP) formation from fluoxetine was determined in human liver microsomes from three homozygous (wt/wt) and three heterozygous (wt/m1) extensive metabolizers (EMs) and three poor metabolizers (PMs) with m1 mutation (m1/m1) with respect to CYP2C19. The formation rate of TFMP was determined by gas chromatograph with electron-capture detection. The kinetics of TFMP formation was best described by the two-enzyme and single-enzyme Michaelis-Menten equation for liver microsomes from CYP2C19 EMs and PMs, respectively. The mean intrinsic clearance (V(max)/K(m)) for the high- and low-affinity component was 25.2 microl/min/nmol and 3.8 microl/min/nmol of cytochrome P450 in the homozygous EMs microsomes and 12.8 microl/min/nmol and 2.9 microl/min/nmol of cytochrome P450 in the heterozygous EMs microsomes, respectively. Omeprazole (a CYP2C19 substrate) at a high concentration and triacetyloleandomycin (a selective inhibitor of CYP3A4) substantially inhibited O-dealkylation of fluoxetine. Furthermore, fluoxetine O-dealkylation was correlated significantly with S-mephenytoin 4'-hydroxylation at a low substrate concentration and midazolam 1'-hydroxylation at a high substrate concentration in liver microsomes of 11 Chinese individuals, respectively. Moreover, there were obvious differences in the O-dealkylation of fluoxetine in liver microsomes from different CYP2C19 genotypes and in microsomal fractions of different human-expressed lymphoblast P450s. The results demonstrated that polymorphic CYP2C19 and CYP3A4 enzymes were the major cytochrome P450 isoforms responsible for fluoxetine O-dealkylation, whereas CYP2C19 catalyzed the high-affinity O-dealkylation of fluoxetine, and its contribution to this metabolic reaction was gene dose-dependent.

World Federation of Societies of Biological Psychiatry (WFSBP) Guidelines for Biological Treatment of Unipolar Depressive Disorders, Part 1: Acute and continuation treatment of major depressive disorder

These practice guidelines for the biological treatment of unipolar depressive disorders were developed by an international Task Force of the World Federation of Societies of Biological Psychiatry (WFSBP). The goal for developing these guidelines was to systematically review all available evidence pertaining to the treatment of unipolar depressive disorders, and to produce a series of practice recommendations that are clinically and scientifically meaningful based on the available evidence. These guidelines are intended for use by all physicians seeing and treating patients with these conditions. The data used for developing these guidelines have been extracted primarily from various national treatment guidelines and panels for depressive disorders, as well as from meta-analyses and reviews on the efficacy of antidepressant medications and other biological treatment interventions identified by a search of the MEDLINE database and Cochrane Library. The identified literature was evaluated with respect to the strength of evidence for its efficacy and was then categorized into four levels of evidence (A-D). This first part of the guidelines covers disease definition, classification, epidemiology and course of unipolar depressive disorders, as well as the management of the acute and continuation-phase treatment. These guidelines are primarily concerned with the biological treatment (including antidepressants, other psychopharmacological and hormonal medications, electroconvulsive therapy, light therapy, adjunctive and novel therapeutic strategies) of young adults and also, albeit to a lesser extent, children, adolescents and older adults.

The Comorbidity of Major Depression and Anxiety Disorders: Recognition and Management in Primary Care

BACKGROUND: Depressive and anxiety disorders commonly occur together in patients presenting in the primary care setting. Although recognition of individual depressive and anxiety disorders has increased substantially in the past decade, recognition of comorbidity still lags. The current report reviews the epidemiology, clinical implications, and management of comorbidity in the primary care setting. METHOD: Literature was reviewed by 2 methods: (1) a MEDLINE search (1980-2001) using the key words depression, depressivedisorders, and anxietydisorders; comorbidity was also searched with individual anxiety diagnoses; and (2) direct search of psychiatry, primary care, and internal medicine journals over the past 5 years. RESULTS: Between 10% and 20% of adults in any given 12-month period will visit their primary care physician during an anxiety or depressive disorder episode (although typically for a nonpsychiatric complaint); more than 50% of these patients suffer from a comorbid second depressive or anxiety disorder. The presence of depressive/anxiety comorbidity substantially increases medical utilization and is associated with greater chronicity, slower recovery, increased rates of recurrence, and greater psychosocial disability. Typically, long-term treatment is indicated, although far less research is available to guide treatment decisions. Selective serotonin reuptake inhibitor antidepressants are the preferred treatment based on efficacy, safety, and tolerability criteria. Knowledge of their differential clinical and pharmacokinetic profiles can assist in optimizing treatment. CONCLUSION: Increased recognition of the high prevalence and negative psychosocial impact of depression and anxiety disorder comorbidity will lead to more effective treatment. While it is hoped that early and effective intervention will yield long-term benefits, research is needed to confirm this.

Influence of antidepressant pharmacotherapy on behavioral treatment adherence and smoking cessation outcome in a combined treatment involving fluoxetine

The authors examined whether serum fluoxetine levels influence behavioral treatment adherence and smoking cessation outcome. Nondepressed smokers (N = 989) from 16 centers were randomized on a double-blind basis to receive either fluoxetine (30 or 60 mg) or placebo plus 9 sessions of behavioral smoking cessation treatment. Fluoxetine and norfluoxetine blood levels were assayed 1 week after the quit date. Logistic regression was used to predict treatment completion and cessation outcome, controlling for gender, age, treatment site, and degree of nicotine dependence. Higher steady-state fluoxetine blood levels (fluoxetine + norfluoxetine) predicted less likelihood of dropping out, chi2(1, N = 820) = 3.9, p < .05, and more likelihood of being abstinent, chi2(1, N = 513) = 18.1, p < .001. Attaining a higher fluoxetine blood level improved the likelihood of completing behavioral treatment and increased the probability of achieving abstinence.

Effects of norfluoxetine, the major metabolite of fluoxetine, on the cloned neuronal potassium channel Kv3.1

The effects of fluoxetine and its major metabolite, norfluoxetine, were studied using the patch-clamp technique on the cloned neuronal rat K(+) channel Kv3.1, expressed in Chinese hamster ovary cells. In whole-cell recordings, fluoxetine and norfluoxetine inhibited Kv3.1 currents in a reversible concentration-dependent manner, with an IC(50) value and a Hill coefficient of 13.11+/-0.91 microM and 1.33+/-0.08 for fluoxetine and 0.80+/-0.06 microM and 1.65+/-0.08 for norfluoxetine at +40 mV, respectively. In inside-out patches, norfluoxetine applied to the cytoplasmic surface inhibited Kv3.1 with an IC(50) value of 0.19+/-0.01 microM. The inhibition of Kv3.1 currents by both drugs was characterized by an acceleration in the apparent rate of current decay, without modification of the activation time course and with relatively fewer effects on peak amplitude. The degree of inhibition of Kv3.1 by norfluoxetine was voltage-dependent. The inhibition increased steeply between 0 and +30 mV, which corresponded with the voltage range for channel opening. In the voltage range positive to +30 mV, inhibition displayed a weak voltage dependence, consistent with an electrical distance delta of 0.31+/-0.05. The association (k(+1)) and dissociation (k(-1)) rate constants for norfluoxetine-induced inhibition of Kv3.1 were 21.70+/-3.39 microM(-1) s(-1) and 14.68+/-3.94 s(-1), respectively. The theoretical K(D) value derived by k(-1)/k(+1) yielded 0.68 microM. Norfluoxetine did not affect the ion selectivity of Kv3.1. The reversal potential under control conditions was about -85 mV and was not affected by norfluoxetine. Norfluoxetine slowed the deactivation time course, resulting in a tail crossover phenomenon when the tail currents, recorded in the presence and absence of norfluoxetine, were superimposed. The voltage dependence of steady-state inactivation was not changed by the drug. Norfluoxetine produced use-dependent inhibition of Kv3.1 at a frequency of 1 Hz and slowed the recovery from inactivation. It is concluded that at clinically relevant concentrations, both fluoxetine and its major metabolite norfluoxetine inhibit Kv3.1, and that norfluoxetine directly inhibits Kv3.1 as an open channel blocker.

Fluvoxamine but not sertraline inhibits the metabolism of olanzapine: evidence from a therapeutic drug monitoring service

Therapeutic drug monitoring data of the new atypical neuroleptic drug olanzapine were used to study interactions with the selective serotonin reuptake inhibitors fluvoxamine and sertraline. The distribution of the ratio of concentration/daily dose (C/D; ng/mL per mg/d) of olanzapine was compared in three groups: patients treated with olanzapine (n = 134), patients treated with olanzapine plus fluvoxamine (n = 10) concomitantly, and patients treated with olanzapine plus sertraline (n = 21) concomitantly. No significant difference was seen between the olanzapine and the olanzapine plus sertraline groups. Patients receiving fluvoxamine in addition to olanzapine had C/D ratios that were in the mean 2.3-fold higher than patients receiving olanzapine without additional fluvoxamine. This indicated that fluvoxamine inhibits the metabolism of olanzapine, probably because of inhibition of cytochrome P450 (CYP) 1A2, whereas sertraline is unlikely to interfere with the metabolism of olanzapine. Combination therapy of olanzapine and fluvoxamine should be used cautiously, and therapeutic drug monitoring should be instituted to avoid olanzapine-induced adverse effects or intoxications.

Urinary retention caused after fluoxetine-risperidone combination

A case of urinary retention emerging after fluoxetine (20 mg/day) addition to low risperidone doses (2 mg/day) is presented. Severe extrapyramidal side-effects (EPS) also occurred after fluoxetine-risperidone combination. Several possibilities, based on the pharmacodynamic and pharmacokinetic properties of risperidone and fluoxetine, which merit consideration in an attempt to explain our patient's side-effects, are discussed. Extrapyramidal side-effects can be due to an increase of the plasma concentration of risperidone and/or the intrinsic propensity of fluoxetine to produce EPS. Urinary retention may be the consequence of a central serotoninergic mechanism in, or without, combination central D2 blockade.

Cellular localization and regional distribution of CYP2D6 mRNA and protein expression in human brain

The cytochrome P4502D6 (CYP2D6) is involved in the biotransformation of many drugs which predominantly act in the central nervous system (CNS), including opioids, various psychotrophic drugs and neurotoxins. Until now, however, only controversial information is available regarding the presence of CYP2D6 in CNS. In this study, the regional and cellular expression of CYP2D6 transcripts and proteins in postmortem brain tissues of three individuals was analysed. A combination of in-situ hybridization coupled with immunohistochemistry on adjacent sections allowed simultaneous detection of CYP2D6 mRNA and protein. However, discrepancies existed in the results such that the mRNA was more widely distributed in the brain areas analysed compared to the protein. Neuronal cells, as well as glial cells, showed labelling for mRNA in brain regions such as the neocortex, caudate nucleus, putamen, globus pallidus, hippocampus, hypothalamus, thalamus, substantia nigra and cerebellum. In contrast, CYP2D6 protein was primarily localized in large principal neurons such as pyramidal cells of the cortex, pyramidal cells of the hippocampus, and Purkinje cells of the cerebellum. In glial cells, CYP2D6 protein was absent. These results provide clear evidence of CYP2D6 expression in certain regions of the CNS and may indicate the role CYP2D6 plays in a number of drug interactions that are of potential clinical importance for neurological diseases.

The selective serotonin reuptake inhibitor sertraline: its profile and use in psychiatric disorders

The naphthylamine derivative sertraline is a potent and selective inhibitor of serotonin reuptake into presynaptic terminals. Sertraline has a linear pharmacokinetic profile and a half-life of about 26 h. Its major metabolite, desmethylsertraline does not appear to inhibit serotonin reuptake. Sertraline mildly inhibits the CYP2D6 isoform of the cytochrome P450 system but has little effect on CYP1A2, CYP3A3/4, CYP2C9, or CYP2C19. It is, however, highly protein bound and may alter blood levels of other highly protein bound agents. Sertraline is a widely used serotonin reuptake inhibitor that has been shown to have both antidepressant and antianxiety effects. Many clinical trials have demonstrated its efficacy in depression compared with both placebo and other antidepressant drugs. Its efficacy has also been demonstrated in randomized, controlled trials of patients with obsessive-compulsive disorder, panic disorder, social phobia, and premenstrual dysphoric disorder. In short-term, open-label studies it has appeared efficacious and tolerable in children and adolescents and in the elderly, and data are positive for its use in pregnant or lactating women. Typical side effects include gastrointestinal and central nervous system effects as well as treatment-emergent sexual dysfunction; withdrawal reactions may be associated with abrupt discontinuation of the agent. The safety profile of sertraline in overdose is very favorable. Sertraline's efficacy for both mood and anxiety disorders, relatively weak effect on the cytochrome P450 system, and tolerability profile and safety in overdose are factors that contribute to make it a first-line agent for treatment in both primary and tertiary care settings.

Fluvoxamine as an adjunctive agent in schizophrenia

Schizophrenia is a common mental disorder that has an early onset and rates high as a cause of medical disability. Antipsychotic agents are the mainstay of treatment but response is often inadequate. Negative symptoms (disturbances in volition, social interaction and affective functions) are particularly difficult to treat and form a major obstacle to rehabilitation. A promising approach to improve response of negative symptoms has been to add a selective serotonin reuptake inhibitor (SSRI) antidepressant to antipsychotic treatment. This review examines evidence pertaining to the efficacy, tolerability, and safety of the SSRI fluvoxamine, combined with antipsychotic agents, in the treatment of negative symptoms in schizophrenia. Important methodological issues, such as differentiating primary and secondary negative symptoms, are discussed. The balance of available evidence indicates that fluvoxamine can improve primary negative symptoms in chronic schizophrenia patients treated with typical antipsychotics and suggests that it may also do so in some patients treated with clozapine. This combination is generally safe and well tolerated although, as antipsychotic drug concentrations may be elevated, attention to dose and drug monitoring should be considered appropriately. Combination with clozapine may require particular caution because of potential toxicity if serum clozapine levels rise steeply. The fluvoxamine doses effective in augmentation are lower than those usually used to treat depression. Evidence regarding the use of fluvoxamine augmentation to treat phenomena, such as obsessions and aggression, which may be associated with schizophrenia, is also examined. An important goal of future studies will be to define which patient groups can benefit from combined treatment.