Venlafaxine (Effexor): concerns about increased risk of fatal outcomes in overdose

Toxicological Assessment of Venlafaxine: Acute and Subchronic Toxicity Study in Rats

Antidepressants are the most commonly prescribed drugs for psychiatric treatment, and venlafaxine (VEN) is one of the most popular options. Venlafaxine is a nontricyclic dual-acting serotonin-norepinephrine reuptake inhibitor. Although an increased incidence of acute toxicity and addiction has been reported, controlled studies examining its toxic effects on different organs are still lacking. This study investigated the possible toxic effects of VEN on the liver, kidney, and gastric tissues. Three groups of rats were administered saline, a single LD₅₀ dose (350 mg/kg), or 100 mg/kg VEN daily, followed by increases in the dose of 50 mg/kg every 10 days for 30 days (about 10 times the therapeutic doses). The following parameters of liver and kidney injury were then assayed: alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transferase, prothrombin time, partial thromboplastin time, blood urea nitrogen, and serum creatinine. A histopathological examination was then conducted. Both acute and subchronic administration of VEN produced multiple clinical manifestations in the experimental animals, including seizures, coma, and even death. Moreover, the liver and renal function tests indicated injury in these tissues. Furthermore, the histopathological examination showed signs of organ toxicity after both acute and chronic VEN exposure. This study has shown that VEN has harmful effects on the liver, kidney, and stomach in either a single high dose (LD₅₀) or repeated exposure to 10 times the therapeutic doses. As a result, strategies to increase awareness of these effects among physicians and the public are needed because this drug may be addictive.

New antidepressant use in older adults: a Canadian population-based study (1997-2013)

OBJECTIVE

There has been much attention on appropriate prescribing in older adults in recent years. Recent guidelines favor the use of newer antidepressants over older agents based on their safety profile in this population. This study aimed to examine whether there has been a decline in older antidepressants and an increase in newer antidepressants used by older adults.

METHOD

A retrospective cross-sectional study using administrative databases examined the annual incidence of antidepressant use (per 1000) of community-dwelling adults ≥60 years old between 1997/1998 and 2012/2013 in Manitoba, Canada.

RESULTS

The population of Manitoba ≥60 years increased by 25.6% from 188,296 to 236,569 from 1997/1998 to 2012/2013. New antidepressant use peaked to 45.9 per 1000 in 1999/2000, and then decreased steadily to 30.5 per 1000 in 2012/2013 (p < 0.0001). Incident amitriptyline use was high but declined from 15.5 to 7.4 per 1000 (p < 0.001). An increase in incident trazodone, mirtazapine, and venlafaxine use was observed (p < 0.001).

CONCLUSIONS

There has been an overall decrease in the annual incidence of antidepressant users in older adults over the last 16 years, with a marked decline in new amitriptyline use and an increase in the incidence of newer agents.

Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders

OBJECTIVES

To provide guidance for the management of mood disorders, based on scientific evidence supplemented by expert clinical consensus and formulate recommendations to maximise clinical salience and utility.

METHODS

Articles and information sourced from search engines including PubMed and EMBASE, MEDLINE, PsycINFO and Google Scholar were supplemented by literature known to the mood disorders committee (MDC) (e.g., books, book chapters and government reports) and from published depression and bipolar disorder guidelines. Information was reviewed and discussed by members of the MDC and findings were then formulated into consensus-based recommendations and clinical guidance. The guidelines were subjected to rigorous successive consultation and external review involving: expert and clinical advisors, the public, key stakeholders, professional bodies and specialist groups with interest in mood disorders.

RESULTS

The Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders (Mood Disorders CPG) provide up-to-date guidance and advice regarding the management of mood disorders that is informed by evidence and clinical experience. The Mood Disorders CPG is intended for clinical use by psychiatrists, psychologists, physicians and others with an interest in mental health care.

CONCLUSIONS

The Mood Disorder CPG is the first Clinical Practice Guideline to address both depressive and bipolar disorders. It provides up-to-date recommendations and guidance within an evidence-based framework, supplemented by expert clinical consensus.

MOOD DISORDERS COMMITTEE

Professor Gin Malhi (Chair), Professor Darryl Bassett, Professor Philip Boyce, Professor Richard Bryant, Professor Paul Fitzgerald, Dr Kristina Fritz, Professor Malcolm Hopwood, Dr Bill Lyndon, Professor Roger Mulder, Professor Greg Murray, Professor Richard Porter and Associate Professor Ajeet Singh.

INTERNATIONAL EXPERT ADVISORS

Professor Carlo Altamura, Dr Francesco Colom, Professor Mark George, Professor Guy Goodwin, Professor Roger McIntyre, Dr Roger Ng, Professor John O'Brien, Professor Harold Sackeim, Professor Jan Scott, Dr Nobuhiro Sugiyama, Professor Eduard Vieta, Professor Lakshmi Yatham.

AUSTRALIAN AND NEW ZEALAND EXPERT ADVISORS

Professor Marie-Paule Austin, Professor Michael Berk, Dr Yulisha Byrow, Professor Helen Christensen, Dr Nick De Felice, A/Professor Seetal Dodd, A/Professor Megan Galbally, Dr Josh Geffen, Professor Philip Hazell, A/Professor David Horgan, A/Professor Felice Jacka, Professor Gordon Johnson, Professor Anthony Jorm, Dr Jon-Paul Khoo, Professor Jayashri Kulkarni, Dr Cameron Lacey, Dr Noeline Latt, Professor Florence Levy, A/Professor Andrew Lewis, Professor Colleen Loo, Dr Thomas Mayze, Dr Linton Meagher, Professor Philip Mitchell, Professor Daniel O'Connor, Dr Nick O'Connor, Dr Tim Outhred, Dr Mark Rowe, Dr Narelle Shadbolt, Dr Martien Snellen, Professor John Tiller, Dr Bill Watkins, Dr Raymond Wu.

A comparison of venlafaxine and SSRIs in deliberate self-poisoning

To compare the clinical features of deliberate self-poisoning with venlafaxine and selective serotonin reuptake inhibitors (SSRIs) presenting to the emergency department of an Australian tertiary referral hospital. A retrospective cohort study comparing all 36 patients who presented with venlafaxine self-poisoning with 44 randomly selected patients with SSRI self-poisoning between 1997 and 2006. Patients who had overdosed on venlafaxine were older (mean age 37.4 versus 28.8 years, p ≤ 0.001) and generally exhibited a higher degree of suicidal intent (p ≤ 0.017). Median venlafaxine dose taken was 35 defined daily doses (DDDs) compared with SSRIs 19.4 DDDs. Those who ingested venlafaxine were more likely to become confused (25% versus 0%; p = 0) and have mydriasis (19.4% versus 2%; p ≤ 0.02), than those who took SSRIs. One patient from the venlafaxine group died. Compared with SSRI self-poisoners, patients who deliberately ingested venlafaxine were more likely to exhibit serious suicide intent. They were also more likely to be older, take a higher DDD of the drug, and have confusion and mydriasis. This has implications for management of severely depressed and suicidal patients.

Fatal venlafaxine poisonings are associated with a high prevalence of drug interactions

Venlafaxine (VEN) is an antidepressant found to possess a higher fatal toxicity index (FTI, i.e., deaths in proportion to consumption) than other newer antidepressants and selective serotonin reuptake inhibitors (SSRIs). The aim of this study was to elucidate using post-mortem cases whether the apparent high toxicity of VEN is associated with adverse drug interactions, pharmacogenetic factors and/or the manner of death. Within a 2-year period, a comprehensive post-mortem database and death certificates were searched for cases with laboratory findings of VEN, findings of other drugs, associated background information and the cause and manner of death. In 123 cases, the concentrations of VEN and its two metabolites, O-desmethylvenlafaxine (O-VEN) and N-desmethylvenlafaxine (N-VEN), and the CYP2D6 genotype were determined in post-mortem blood. The median concentrations of VEN, O-VEN and N-VEN were 560, 420 and 49 µg/l, respectively. A prominent feature of the VEN-positive cases was the high abundance of interacting drugs (46%), being more common with higher VEN concentrations. Compared to other common antidepressants, VEN-positive cases showed the highest suicide frequency, but also the proportion of suicidal VEN poisonings of all suicides was substantially higher than that of mirtazapine or SSRIs. Relative CYP2D6 activity did not predispose to high VEN concentrations, and the frequency of the extreme phenotypes followed the general population. In conclusion, the high suicide potential of VEN in combination with the high prevalence of drugs causing adverse interactions could be the reason for the observed high FTI.

Canadian Network for Mood and Anxiety Treatments (CANMAT) clinical guidelines for the management of major depressive disorder in adults. III. Pharmacotherapy

BACKGROUND

In 2001, the Canadian Psychiatric Association and the Canadian Network for Mood and Anxiety Treatments (CANMAT) partnered to produce evidence-based clinical guidelines for the treatment of depressive disorders. A revision of these guidelines was undertaken by CANMAT in 2008-2009 to reflect advances in the field.

METHODS

The CANMAT guidelines are based on a question-answer format to enhance accessibility to clinicians. An evidence-based format was used with updated systematic reviews of the literature and recommendations were graded according to Level of Evidence using pre-defined criteria. Lines of Treatment were identified based on criteria that included Levels of Evidence and expert clinical support. This section on "Pharmacotherapy" is one of 5 guideline articles.

RESULTS

Despite emerging data on efficacy and tolerability differences amongst newer antidepressants, variability in patient response precludes identification of specific first choice medications for all patients. All second-generation antidepressants have Level 1 evidence to support efficacy and tolerability and most are considered first-line treatments for MDD. First-generation tricyclic and monoamine oxidase inhibitor antidepressants are not the focus of these guidelines but generally are considered second- or third-line treatments. For inadequate or incomplete response, there is Level 1 evidence for switching strategies and for add-on strategies including lithium and atypical antipsychotics.

LIMITATIONS

Most of the evidence is based on trials for registration and may not reflect real-world effectiveness.

CONCLUSIONS

Second-generation antidepressants are safe, effective and well tolerated treatments for MDD in adults. Evidence-based switching and add-on strategies can be used to optimize response in MDD that is inadequately responsive to monotherapy.

Efficacy of venlafaxine compared with tricyclic antidepressants in depressive disorder: a meta-analysis

With respect to the pharmacological characteristic, venlafaxine is comparable with tricyclic antidepressants (TCAs), and venlafaxine might be comparable in efficacy. We performed a systematic review investigating the relative efficacy and tolerability of venlafaxine compared with TCAs (imipramine, clomipramine, amitriptyline, nortriptyline and desipramine). Relevant double-blind randomised trials were identified from systematic searches of electronic databases. An exact analysis of the estimated odds ratios of response of the TCA relative to venlafaxine showed no overall significance of treatment effect (P = 0.38). The odds ratios were not homogenous across studies (P = 0.0213). The average dose of venlafaxine was 103.5 mg/day and for the TCA 106.1 mg/day. An exact analysis of the estimated odds ratios of the withdrawals and side effects in the trials with a TCA relative to venlafaxine showed no overall significance of withdrawal. From our review, no significant difference in treatment effect between low dose of both venlafaxine and the TCAs could be found. In our opinion, because of the heterogeneity of the odds ratios, one cannot conclude that they are of equal efficacy.