Debate resolved: there are differential effects of serotonin selective reuptake inhibitors on cytochrome P450 enzymes

Pharmacogenomics and Global Precision Medicine in the Context of Adverse Drug Reactions: Top 10 Opportunities and Challenges for the Next Decade

In a move indicative of the enthusiastic support of precision medicine, the U.S. President Barack Obama announced the Precision Medicine Initiative in January 2015. The global precision medicine ecosystem is, thus, receiving generous support from the United States ($215 million), and numerous other governments have followed suit. In the context of precision medicine, drug treatment and prediction of its outcomes have been important for nearly six decades in the field of pharmacogenomics. The field offers an elegant solution for minimizing the effects and occurrence of adverse drug reactions (ADRs). The Clinical Pharmacogenetics Implementation Consortium (CPIC) plays an important role in this context, and it aims at specifically guiding the translation of clinically relevant and evidence-based pharmacogenomics research. In this forward-looking analysis, we make particular reference to several of the CPIC guidelines and their role in guiding the treatment of highly relevant diseases, namely cardiovascular disease, major depressive disorder, cancer, and human immunodeficiency virus, with a view to predicting and managing ADRs. In addition, we provide a list of the top 10 crosscutting opportunities and challenges facing the fields of precision medicine and pharmacogenomics, which have broad applicability independent of the drug class involved. Many of these opportunities and challenges pertain to infrastructure, study design, policy, and science culture in the early 21st century. Ultimately, rational pharmacogenomics study design and the acquisition of comprehensive phenotypic data that proportionately match the genomics data should be an imperative as we move forward toward global precision medicine.

The nematode Caenorhabditis elegans as a tool to predict chemical activity on mammalian development and identify mechanisms influencing toxicological outcome

To determine whether a C. elegans bioassay could predict mammalian developmental activity, we selected diverse compounds known and known not to elicit such activity and measured their effect on C. elegans egg viability. 89% of compounds that reduced C. elegans egg viability also had mammalian developmental activity. Conversely only 25% of compounds found not to reduce egg viability in C. elegans were also inactive in mammals. We conclude that the C. elegans egg viability assay is an accurate positive predictor, but an inaccurate negative predictor, of mammalian developmental activity. We then evaluated C. elegans as a tool to identify mechanisms affecting toxicological outcomes among related compounds. The difference in developmental activity of structurally related fungicides in C. elegans correlated with their rate of metabolism. Knockdown of the cytochrome P450s cyp-35A3 and cyp-35A4 increased the toxicity to C. elegans of the least developmentally active compounds to the level of the most developmentally active. This indicated that these P450s were involved in the greater rate of metabolism of the less toxic of these compounds. We conclude that C. elegans based approaches can predict mammalian developmental activity and can yield plausible hypotheses for factors affecting the biological potency of compounds in mammals.

Cytochrome P450 CYP1A2, CYP2C9, CYP2C19 and CYP2D6 genes are not associated with response and remission in a sample of depressive patients

Cytochrome P450 genes are involved in the metabolism of antidepressants and could influence treatment response. The aim of this study was to investigate the role of allelic variations of the cytochrome P450 CYP1A2, CYP2C9, CYP2C19 and CYP2D6 genes in antidepressant treatment response and remission rates. Two hundred and seventy-eight patients affected by major depression, responders (N = 81) and nonresponders (N=197) to at least one adequate antidepressant treatment, were recruited with a multicentre design for resistant depression and genotyped for all relevant variations. None of the considered metabolic profiles (e.g. poor, intermediate, extensive and ultrarapid metabolizers) was found to be associated with either response or remission rates. In conclusion, the investigated cytochrome genes do not seem to play a major role in antidepressant response in the present sample of depressive patients. Nevertheless, methodological and sample size limitations of this study do not allow definitive conclusions.

Fluoxetina: indícios de uso inadequado

OBJETIVO: Investigar o uso da fluoxetina na cidade de Santo André, SP, por meio de coleta e análise das receitas especiais (RE) prescritas por médicos e arquivadas nas farmácias e drogarias daquela cidade. MÉTODOS: Foram coletadas as receitas especiais retidas durante os meses de agosto do ano de 2005 a julho de 2006, em 13 farmácias de manipulação e em 27 drogarias em diferentes regiões de Santo André. Cada receita especial foi analisada em relação à presença de fluoxetina, em associação ou não a outros princípios ativos, e o sexo do(a) paciente foi anotado. RESULTADOS: Foram analisadas 39.782 RE - 16.124 coletadas das farmácias magistrais e 23.658 das drogarias. Desses totais, 10.919 prescrições continham fluoxetina - 9.259 provenientes das farmácias magistrais (84,8%) e apenas 1.660 (15,2%) das drogarias. As prescrições de fluoxetina eram predominantemente destinadas a mulheres (79,8%). Na imensa maioria das RE, a fluoxetina foi prescrita em associação com um grande número de outras substâncias ativas, inclusive anfetaminas anoréticas, chegando a mais de dez outras em quase a metade das prescrições. Esse tipo de prescrição múltipla, principalmente para mulheres, é comparado com as prescrições de fórmulas magistrais para emagrecer, muito utilizadas no Brasil. CONCLUSÃO: Os dados obtidos sugerem que a utilização de fluoxetina teria um fim estético (perda de peso), e não um fim terapêutico (tratamento de depressão). Discute-se a relação risco-benefício desse possível uso, que poderia ser classificado de inadequado dado as conhecidas reações adversas da fluoxetina e a sua interferência no sistema citocromo P450.

A comparison of the chronic treatment effects of venlafaxine and other antidepressants on serotonin and norepinephrine transporters

BACKGROUND

Venlafaxine blocks both serotonin and norepinephrine transporters (SERT and NET), with higher affinity for SERT. Serotonergic effects occur with lower doses, whereas both serotonergic and noradrenergic effects occur with higher doses of venlafaxine. Chronic treatment of rats with selective serotonin reuptake inhibitors decreases SERT binding sites, whereas similar treatment with selective norepinephrine reuptake inhibitors decreases NET binding sites. We hypothesized that venlafaxine would affect monoamine transporters dose-dependently, with low doses causing selective reduction of SERT binding sites and higher doses reducing both SERT and NET binding sites.

METHODS

Rats were treated for 21 days with a low (15 mg/kg/day) or high (70 mg/kg/day) dose of venlafaxine, vehicle, or other antidepressants. The SERT and NET density was determined by quantitative autoradiography.

RESULTS

Neither dose of venlafaxine nor amitriptyline reduced binding to either the SERT or NET. In rats with noradrenergic terminals destroyed by 6-hydroxydopamine, venlafaxine still failed to reduce SERT binding. Also, rats treated simultaneously with sertraline plus desipramine exhibited reductions in both SERT and NET binding.

CONCLUSIONS

Chronic venlafaxine treatment affected SERT and NET binding differently from paroxetine or desipramine. The inability of venlafaxine to reduce SERT or NET binding sites is not due to its dual uptake inhibiting properties.

New possibilities of treatment for panic attacks in elderly patients: escitalopram versus citalopram

PURPOSE

Panic attacks may represent additional therapeutic problems in the elderly. The utility of citalopram in panic attacks has been widely investigated. Here, we compare the efficacy and safety of citalopram, with its S-enantiomer escitalopram at half dosage as to citalopram, in elderly patients who have panic attacks.

METHODS

This was an open community-based study. Forty patients who have panic attacks, according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria, were enrolled. Fifty percent of the patients were assigned for 8 weeks' treatment with escitalopram, and the remaining 50% were assigned to treatment with citalopram. The primary outcome measure was the weekly rate of panic attacks. The secondary outcome measures were the Hamilton scale for anxiety and depression and the Cooper Disability Scale. Analysis of variance by repeated measures was applied to calculate differences between groups.

RESULTS

A similar decrease in weekly rate of panic attacks, in the scores of Hamilton Scale for anxiety and depression and in the Cooper Disability Scale scores, was observed in both groups after 8 weeks, but a significant variation of outcome measures from baseline was observed already after 2 weeks in the escitalopram group (P < 0.001) and only after 4 weeks in the citalopram group (P < 0.01).

CONCLUSIONS

Escitalopram could be considered among the drugs of first choice in elderly patients with panic attacks because of its good efficacy and safety and for the advantage of reducing the total dose and of a more rapid onset of action as compared with citalopram, although further studies are needed to confirm these results.

Inhibitory effects of psychotropic drugs on mexiletine metabolism in human liver microsomes: prediction of in vivo drug interactions

Mexiletine, an anti-arrhythmic agent, is used for the control of ventricular arrhythmias and for neuropathic pain from cancer or diabetes mellitus. It is sometimes used together with psychotropic drugs in patients with depression, schizophrenia or sleep disorder. It is metabolized mainly by cytochrome P450 (CYP) 2 D 6 and, to a minor extent, by CYP1A2. To predict possible drug interactions between mexiletine and psychotropic drugs, the inhibitory effects of 14 psychotropic drugs (phenytoin, carbamazepine, fluvoxamine, paroxetine, fluoxetine, citalopram, sertraline, imipramine, desipramine, haloperidol, thioridazine, olanzapine, etizolam, and quazepam) on mexiletine metabolism in human liver microsomes were determined. Fluoxetine (Ki=0.6+/- 0.1 microM), sertraline (Ki=7.6+/- 0.8 microM) and desipramine (Ki=3.2+/- 0.5 microM) competitively inhibited the mexiletine p-hydroxylation in human liver microsomes. Thioridazine (Kis=0.5+/- 0.2 microM; Kii =3.6+/-1.6 microM) and paroxetine (Kis=1.7+/- 0.7 microM; Kii=3.6+/- 0.9 microM) exhibited a mixed-type inhibition (competitive and non-competitive) toward mexiletine p-hydroxylation in human liver microsomes. The changes of the in vivo clearance of mexiletine by the psychotropic drugs were predicted by 1+(I/Ki) using the in vitro Ki and unbound inhibitor concentrations in liver. The values were calculated as 2.4 for paroxetine, 5.5 for fluoxetine, 1.1 for sertraline, 2.8 for desipramine and 2.2 for thioridazine. In addition, paroxetine exhibited a mechanism-based inactivation with Ki=0.7 microM and Kinact=0.15 min(-1). The present study predicted the possibility of drug interactions between mexiletine and paroxetine, fluoxetine, desipramine, and thioridazine in clinical use.

Escitalopram: A New SSRI for the Treatment of Depression in Primary Care

Escitalopram is the S-enantiomer of the racemic compound citalopram, a selective serotonin reuptake inhibitor (SSRI) widely used for the treatment of depression. This review describes the current body of pharmacologic and clinical evidence supporting the use of escitalopram for the treatment of depression and anxiety. Preclinical studies have confirmed that it is primarily this molecule that provides the inhibition of serotonin reuptake responsible for the antidepressant effect of citalopram, with minimal-to-nonexistent affinity for other receptor sites. Clinical trials of escitalopram in depressed patients indicate that escitalopram, 10 mg/day, is as effective as 40 mg/day of its parent compound, citalopram, with an excellent safety and tolerability profile. Because of its increased selectivity, escitalopram represents a refinement in SSRI therapy for symptoms of depression and anxiety. This article also explores the implications of a more selective SSRI on the management of depressed patients in the primary care clinical practice.

Inhibition of risperidone metabolism by fluoxetine in patients with schizophrenia: a clinically relevant pharmacokinetic drug interaction

The effect of fluoxetine on the steady-state plasma concentrations of risperidone and its active metabolite 9-hydroxyrisperidone (9-OH-risperidone) was evaluated in 10 patients with schizophrenia or schizoaffective disorder. Patients stabilized on risperidone (4-6 mg/day) received additional fluoxetine (20 mg/day) to treat concomitant depression. One patient dropped out after 1 week due to the occurrence of akathisia associated with markedly increased plasma risperidone concentrations. In the other subjects, mean plasma concentrations of risperidone increased during fluoxetine administration from 12 +/- 9 ng/mL at baseline to 56 +/- 31 at week 4 (p < 0.001), while the levels of 9-OH-risperidone were not significantly affected. After 4 weeks of combined treatment, the levels of the active moiety (sum of the concentrations of risperidone and 9-OH-risperidone) increased by 75% (range, 9-204%, p < 0.01) compared with baseline. The mean plasma risperidone/9-OH-risperidone ratio also increased significantly. During the second week of adjunctive therapy, two patients developed Parkinsonian symptoms, which were controlled with anticholinergic medication. These findings indicate that fluoxetine, a potent inhibitor of the cytochrome P450 enzyme CYP2D6 and a less potent inhibitor of CYP3A4, reduces the clearance of risperidone by inhibiting its 9-hydroxylation or alternative metabolic pathways. This interaction may lead to toxic plasma risperidone concentrations. In addition to careful clinical observation, monitoring plasma risperidone levels may be of value in patients given adjunctive therapy with fluoxetine.

Paroxetine: an update of its use in psychiatric disorders in adults

Paroxetine is a selective serotonin reuptake inhibitor (SSRI), with antidepressant and anxiolytic activity. In 6- to 24-week well designed trials, oral paroxetine 10 to 50 mg/day was significantly more effective than placebo, at least as effective as tricyclic antidepressants (TCAs) and as effective as other SSRIs and other antidepressants in the treatment of major depressive disorder. Relapse or recurrence over 1 year after the initial response was significantly lower with paroxetine 10 to 50 mg/day than with placebo and similar to that with imipramine 50 to 275 mg/day. The efficacy of paroxetine 10 to 40 mg/day was similar to that of TCAs and fluoxetine 20 to 60 mg/day in 6- to 12-week trials in patients aged > or =60 years with major depression. Paroxetine 10 to 40 mg/day improved depressive symptoms to an extent similar to that of TCAs in patients with comorbid illness, and was more effective than placebo in the treatment of dysthymia and minor depression. Paroxetine 20 to 60 mg/day was more effective than placebo after 8 to 12 weeks' treatment of obsessive-compulsive disorder (OCD), panic disorder, social anxiety disorder (social phobia), generalised anxiety disorder (GAD) and post-traumatic stress disorder (PTSD). Improvement was maintained or relapse was prevented for 24 weeks to 1 year in patients with OCD, panic disorder, social anxiety disorder or GAD. The efficacy of paroxetine was similar to that of other SSRIs in patients with OCD and panic disorder and similar to that of imipramine but greater than that of 2'chlordesmethyldiazepam in patients with GAD. Paroxetine is generally well tolerated in adults, elderly individuals and patients with comorbid illness, with a tolerability profile similar to that of other SSRIs. The most common adverse events with paroxetine were nausea, sexual dysfunction, somnolence, asthenia, headache, constipation, dizziness, sweating, tremor and decreased appetite. In conclusion, paroxetine, in common with other SSRIs, is generally better tolerated than TCAs and is a first-line treatment option for major depressive disorder, dysthymia or minor depression. Like other SSRIs, paroxetine is also an appropriate first-line therapy for OCD, panic disorder, social anxiety disorder, GAD and PTSD. Notably, paroxetine is the only SSRI currently approved for the treatment of social anxiety disorder and GAD, which makes it the only drug of its class indicated for all five anxiety disorders in addition to major depressive disorder. Thus, given the high degree of psychiatric comorbidity of depression and anxiety, paroxetine is an important first-line option for the treatment of major depressive disorder, OCD, panic disorder, social anxiety disorder, GAD and PTSD.

Bupropion SR in the naturalistic treatment of elderly patients with major depression

INTRODUCTION

Bupropion immediate release (IR) and bupropion sustained release (SR) are frequently used to treat geriatric depression, as they have few cardiovascular, gastrointestinal and sexual adverse effects. We sought to examine the efficacy and dosing patterns of bupropion in a naturalistic cohort of elderly subjects with major depression (MD).

METHODS

31 elderly ( > 60 years) patients with unipolar MD (DSM-IV) who were enrolled in Duke's Mental Health Clinical Research Center for the Study of Depression in Later Life were prescribed bupropion SR or IR, alone or in combination with other antidepressant agents, for 12 weeks. Montgomery-Asberg depression rating scale (MADRS) scores and clinical global impression (CGI) severity scores were used to define response.

RESULTS

74% (23/31) of the sample were responders (MADRS < 15) and 53% (16/30) achieved a partial (CGI = 2) or complete (CGI = 1) remission of MD at week 12. Among patients treated with bupropion SR monotherapy, the mean (range) maximal daily dose achieved was 240 mg (150-400 mg). Among those treated with bupropion IR, the mean (range) maximum daily dose achieved was 258 mg (150-450 mg). In subjects on monotherapy, 67% (10/15) of MD subjects were responders (MADRS < 15) and 50% (7/14) achieved full or partial remission. Response rates did not differ statistically among those with high and low medical comorbidity.

CONCLUSIONS

In this naturalistic 12-week study, geriatric MD patients with high and low medical comorbidity responded well to bupropion and bupropion SR. In elderly patients, four to eight week acute treatment periods may be insufficient. Our findings suggest that nearly 50% of elderly depressed subjects at a tertiary center may need combination therapy over the course of their illness. Controlled randomized studies to establish the long-term efficacy and optimal dose of the newer antidepressants in geriatric depression are urgently needed.

Clinical and treatment response characteristics of late-life depression associated with vascular disease: a pooled analysis of two multicenter trials with sertraline

1. The safety and efficacy of sertraline in the treatment of moderate-to-severe major depression in elderly outpatients, aged 60 years and older, with comorbid vascular disease was evaluated. 2. An analysis of the pooled results for the sertraline treatment group drawn from two prospective, randomized, double-blind studies (sertraline vs. fluoxetine, and sertraline vs. nortriptyline) was done. Patients were retrospectively categorized into one of 3 clinical groups: 1) patients with a current diagnosis of hypertension but no other past or present cardiovascular illness (HTN), 2) patients reporting a current or past history of cardiovascular illness, but excluding hypertension (VASC), and 3) patients with no hypertension, and no other comorbid vascular illness (NoVASC). Patients received 12-3. weeks of double-blind treatment with sertraline in flexible daily doses in the range of 50 - 150 mg (in the nortriptyline comparator trial) or 50 - 100 mg (in the fluoxetine comparator trial). 4. Sertraline treatment yielded comparable levels of response in all 3 groups (response criterion: CGI-much or very much improved) at treatment endpoint on both a completer analysis (HTN, 86%; VASC, 89%; NoVASC, 77%) and significantly higher response rates on a 12-week endpoint analysis (HTN, 74%; VASC, 69%; NoVASC, 58%; p < 0.05). Sertraline treatment was well-tolerated, with no between-group differences in rates of adverse events, or in discontinuation due to adverse events. Patients taking 5 or more concomitant medications showed no difference, when compared with patients taking none-or-one concomitant medication, either in rates of adverse events, or in discontinuation due to adverse events. 5. Sertraline was found to be a safe, well-tolerated, and effective as an antidepressant in elderly patients suffering from hypertension and other forms of vascular comorbidity.

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.