Pharmacologic profile and efficacy of venlafaxine

Zygotic Exposure to Venlafaxine Disrupts the Circadian Locomotor Activity Behaviour in Zebrafish Larvae

The antidepressant venlafaxine, a selective serotonin and norepinephrine reuptake inhibitor, is commonly prescribed to treat major depressive disorder and is found at high concentrations in the aquatic environment. Concerns have been raised related to the health of aquatic organisms in response to this nontargeted pharmaceutical exposure. For instance, we previously demonstrated that exposure to venlafaxine perturbs neurodevelopment, leading to behavioural alterations in zebrafish (Danio rerio). We also observed disruption in serotonin expression in the pineal and raphe, regions critical in regulating circadian rhythms, leading us to hypothesize that zygotic exposure to venlafaxine disrupts the circadian locomotor rhythm in larval zebrafish. To test this, we microinjected zebrafish embryos with venlafaxine (1 or 10 ng) and recorded the locomotor activity in 5-day-old larvae over a 24-h period. Venlafaxine deposition reduced larval locomotor activity during the light phase, but not during the dark phase of the diurnal cycle. The melatonin levels were higher in the dark compared to during the light photoperiod and this was not affected by embryonic venlafaxine deposition. Venlafaxine exposure also did not affect the transcript abundance of clock genes, including clock1a, bmal2, cry1a and per2, which showed a clear day/night rhythmicity. A notable finding was that exposure to luzindole, a melatonin receptor antagonist, decreased the locomotor activity in the control group in light, whereas the activity was higher in larvae raised from the venlafaxine-deposited embryos. Overall, zygotic exposure to venlafaxine disrupts the locomotor activity of larval zebrafish fish during the day, demonstrating the capacity of antidepressants to disrupt the circadian rhythms in behaviour. Our results suggest that disruption in melatonin signalling may be playing a role in the venlafaxine impact on circadian behaviour, but further investigation is required to elucidate the possible mechanisms in larval zebrafish.

Treatment-Resistant Depression (TRD): Is the Opioid System Involved?

About 30% of major depression disorder patients fail to achieve remission, hence being diagnosed with treatment-resistant major depression (TRD). Opium had been largely used effectively to treat depression for centuries, but when other medications were introduced, its use was discounted due to addiction and other hazards. In a series of previous studies, we evaluated the antinociceptive effects of eight antidepressant medications and their interaction with the opioid system. Mice were tested with a hotplate or tail-flick after being injected with different doses of mianserin, mirtazapine, trazodone, venlafaxine, reboxetine, moclobemide, fluoxetine, or fluvoxamine to determine the effect of each drug in eliciting antinociception. When naloxone inhibited the antinociceptive effect, we further examined the effect of the specific opioid antagonists of each antidepressant drug. Mianserin and mirtazapine (separately) induced dose-dependent antinociception, each one yielding a biphasic dose-response curve, and they were antagonized by naloxone. Trazodone and venlafaxine (separately) induced a dose-dependent antinociceptive effect, antagonized by naloxone. Reboxetine induced a weak antinociceptive effect with no significant opioid involvement, while moclobemide, fluoxetine, and fluvoxamine had no opioid-involved antinociceptive effects. Controlled clinical studies are needed to establish the efficacy of the augmentation of opiate antidepressants in persons with treatment-resistant depression and the optimal dosage of drugs prescribed.

A review of the efficacy and tolerability of venlafaxine

Venlafaxine is a selective serotonin norepinephrine reuptake inhibitor with no activity at muscarinic, histaminergic or adrenergic receptors. The antidepressant activity of venlafaxine has been demonstrated in placebo-controlled and active comparator-controlled clinical trials. Venlafaxine was effective in outpatients and hospitalized patients with major depression and in those with melancholia, agitated or retarded symptoms, and refractory or treatment-resistant depression. Venlafaxine was at least as effective as comparative antidepressants and was more effective than fluoxetine or imipramine in some trials. A positive dose-response relationship has been shown with venlafaxine. When doses of venlafaxine are titrated rapidly upward, an onset of antidepressant action has been detected within one week in some studies. Venlafaxine is well tolerated during short- and long-term treatment. The most common adverse effects are nausea, somnolence and dry mouth. The overall tolerability of venlafaxine appears to exceed that of tricyclic antidepressants and compares favorably with that of selective serotonin reuptake inhibitors. Venlafaxine is a novel antidepressant that is appropriate for first-line therapy in patients with major depression.

Interaction of different antidepressants with acute and chronic methadone in mice, and possible clinical implications

We studied the interaction of a single dose of different antidepressant medications with a single (acute) dose or implanted mini-pump (chronic) methadone administration in mice, using the hotplate assay. For the acute experiment, subthreshold doses of six antidepressant drugs were administered separately with a single dose of methadone. The addition of a subthreshold dose of desipramine or clomipramine to methadone produced significant augmentation of the methadone effect with each drug (p < 0.05). Fluvoxamine given at a fixed subthreshold dose induced a synergistic effect only with a low methadone dose. Escitalopram, reboxetine and venlafaxine given separately, each at a fixed subthreshold dose, induced no interaction. Possible clinical implications of these findings are that while escitalopram, reboxetine and venlafaxine do not affect methadone's antinociception in mice and are safe to be given together with methadone when indicated, fluvoxamine, clomipramine and desipramine considerably augment methadone-induced effects and should be avoided in this population due to the risk of inducing opiate overdose. For the chromic experiment, when a subthreshold dose of either escitalopram, desipramine or clomipramine was injected to mice following 2 weeks of methadone administration with the mini-pump, none of the antidepressant drugs strengthened methadone's analgesic effect. Further studies are needed before possible clinical implications can be drawn.

Neurotransmitter transporters and their impact on the development of psychopharmacology

The synaptic actions of most neurotransmitters are inactivated by reuptake into the nerve terminals from which they are released, or by uptake into adjacent cells. A family of more than 20 transporter proteins is involved. In addition to the plasma membrane transporters, vesicular transporters in the membranes of neurotransmitter storage vesicles are responsible for maintaining vesicle stores and facilitating exocytotic neurotransmitter release. The cell membrane monoamine transporters are important targets for CNS drugs. The transporters for noradrenaline and serotonin are key targets for antidepressant drugs. Both noradrenaline-selective and serotonin-selective reuptake inhibitors are effective against major depression and a range of other psychiatric illnesses. As the newer drugs are safer in overdose than the first-generation tricyclic antidepressants, their use has greatly expanded. The dopamine transporter (DAT) is a key target for amphetamine and methylphenidate, used in the treatment of attention deficit hyperactivity disorder. Psychostimulant drugs of abuse (amphetamines and cocaine) also target DAT. The amino-acid neurotransmitters are inactivated by other families of neurotransmitter transporters, mainly located on astrocytes and other non-neural cells. Although there are many different transporters involved (four for GABA; two for glycine/D-serine; five for L-glutamate), pharmacology is less well developed in this area. So far, only one new amino-acid transporter-related drug has become available: the GABA uptake inhibitor tiagabine as a novel antiepileptic agent.

Combined effects of venlafaxine, nicotine replacement, and brief counseling on smoking cessation

In this study, 147 smokers were randomly assigned to receive either venlafaxine or placebo in conjunction with behavioral counseling (9 weekly sessions) and transdermal nicotine replacement therapy (22 mg/day). Patients began medication 2 weeks before quitting and continued for 18 weeks after quitting, with the daily dose titrated from 150 to 225 mg. in response to symptoms of negative affect and relapse. The results showed no main effect of treatment on abstinence. Post hoc analysis revealed that both at the end of treatment and at the 1-year follow-up smokers consuming less than a pack of cigarettes a day benefited from the addition of venlafaxine to the treatment regimen. Venlafaxine also reduced negative affect for all smokers for up to 6 weeks postcessation. The findings suggest that venlafaxine could have some role to play in the treatment of lighter smokers, in addition to the expected benefits of nicotine replacement therapy and behavioral counseling.

The Effect of Brochures and Audiotape on Efficacy and Tolerability of Venlafaxine in Depressed Outpatients: A Single-Blind Parallel Study in General Practice

OBJECTIVE: The possible positive effects of brochures and an audiotape containing information on efficacy and tolerance on side effects, dropout rate, and clinical outcome of treatment with venlafaxine were studied in 1048 depressed outpatients (as clinically judged by the general practitioner; 740 women and 308 men), aged 18 to 85 years. METHOD: The study was of a single-blind, parallel-group design. All 4 groups were verbally informed: one group received only verbal information, a second group additionally received brochures, a third group additionally received information on audiotape, and a fourth group additionally received brochures and information on audiotape. There were 5 study visits, the first at baseline (week 0), followed by a visit at weeks 1, 2, 4, and 6. At each study visit, the Clinical Global Impressions scale, Zung Depression Scale, Quality of Life Scale, and State-Trait Anxiety Inventory were completed. The Patient's and Investigator's Subjective Ratings of Tolerance and Efficacy were completed at the final study visit. RESULTS: The brochures and audiotape reduced the dropout rate due to lack of efficacy (p =.01 and p =.04, respectively). In addition, the percentage of patients reporting side effects was lower in the group that received brochures than in the group that received only verbal information (p =.05). Additional information had no effect on efficacy measures. CONCLUSION: Supplying patients with education in the form of brochures and/or audiotape containing information on efficacy and tolerance of the drug reduces the dropout rate due to lack of efficacy. For the reduction of side effects, brochures in particular seem suitable. Information on audiotape or written information seems to lengthen the period that patients wait for the possible beneficial action of the medication. To reduce the dropout rate, it may be recommended that patients receive, in addition to brochures, spoken information on audiotape or compact disc.

The effects of venlafaxine on the subjective, reinforcing, and cardiovascular effects of cocaine in opioid-dependent and non-opioid-dependent humans

The effects of maintenance on venlafaxine, which blocks both norepinephrine and serotonin reuptake, on the response to smoked cocaine (0, 12, 25, or 50 mg) in 7 opioid-free and 7 methadone-maintained cocaine abusers was examined during a 42-day study. Participants received venlafaxine (225 mg daily) and placebo as part of a double-blind crossover design. Cocaine significantly increased heart rate, blood pressure, cocaine choice, cocaine ratings, and ratings of positive subjective effects (e.g., "I feel high") in both groups. Venlafaxine significantly decreased the subjective effects of cocaine by 10-20% without affecting cocaine choice or cardiovascular response in both groups. Although the reduction in cocaine's effects was small, further studies using a longer venlafaxine maintenance period or a larger venlafaxine dose are warranted.

Stereochemistry and drug efficacy and development: relevance of chirality to antidepressant and antipsychotic drugs

Many drugs contain a chiral center or a center of unsaturation, or such centers result during metabolism of these drugs. Often such drugs are marketed as a mixture of the resultant enantiomers (racemates) or of geometric isomers, respectively. These enantiomers (molecules that are not superimposible on their mirror image) or geometric isomers may differ markedly from each other with regard to their pharmacodynamic and/or pharmacokinetic properties. This review deals primarily with drugs with chiral centers, and possible complications arising from the use of racemates are discussed. Recent developments in resolution of enantiomers, increased knowledge of the molecular structure of specific drug targets and a heightened awareness of several possible advantages of using single enantiomers rather than racemic mixtures of drugs have led to an increased emphasis on understanding the role of chirality in drug development. This has resulted in increased investigation of individual enantiomers early on in the development of drugs and in 'chiral switching', i.e. the replacement of a racemate of a drug which has already been approved or marketed by a single enantiomer. Although stereochemistry is an important matter to consider in drugs of virtually all classes, this review focuses on the relevance of chirality to antidepressant and antipsychotic drugs. Examples of the effects of chiral centers on the properties of antidepressants (tricyclics, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, viloxazine, bupropion, mianserin, venlafaxine, mirtazapine and reboxetine), antipsychotics and/or some of their metabolites are discussed.

Novel treatments for anxiety and depression: hurdles in bringing them to the market

Anxiety and depressive disorders are the most common psychiatric conditions. The medical need for newer, better-tolerated and more efficacious treatments remains high. However, drug development is time-consuming and has a high rate of failed or inconclusive trials. Improvements in study design, investigator training and early proof-of-concept studies are being discussed as means to decrease failure rates and the duration of development. So far, no uniformly applicable 'magic formulas' for success have been discovered. The most promising approach to overcome these hurdles appears to be a sound study design carried out by experienced professionals in the clinic and in industry.

SNaRIs, NaSSAs, and NaRIs: new agents for the treatment of depression

A major goal of antidepressant development is to improve on preceding drug classes with agents with greater specificity (and therefore fewer unwanted side-effects) and with more rapid onset of antidepressant action. To this end, four antidepressants with significantly distinct pharmacological characteristics have been recently introduced: venlafaxine, nefazodone, mirtazapine, and reboxetine. Venlafaxine is the first antidepressant in a new drug class referred to as the serotonin noradrenergic reuptake inhibitors (SNaRIs). Nefazodone is a weaker serotonin and norepinephrine reuptake inhibitor, but a potent serotonin 5-HT2 receptor antagonist. Mirtazapine is a potent antagonist of central 2alpha-adrenergic autoreceptors, and heteroreceptors and is an antagonist of serotonin 5-HT2 and 5-HT3 receptors. The result of these actions is to increase both noradrenergic and specific (5-HT1) serotonergic transmission, and mirtazapine has therefore been termed a noradrenergic and specific serotonergic antidepressant (NaSSA). Reboxetine is the first selective noradrenaline reuptake inhibitor (NaRI) to be introduced since the tricyclics, and lacks immediate serotonergic effects.

The antinociceptive effect of venlafaxine in mice is mediated through opioid and adrenergic mechanisms

The antinociceptive effects of the novel phentylethylamine antidepressant drug venlafaxine and its interaction with various opioid, noradrenaline and serotonin receptor subtypes were evaluated. When mice were tested with a hotplate analgesia meter, venlafaxine induced a dose-dependent antinociceptive effect following i.p. administration with an ED50 of 46.7 mg/kg (20.5; 146.5; 95% CL). Opioid, adrenergic and serotoninergic receptor antagonists were tested for their ability to block venlafaxine antinociception. Venlafaxine-induced antinociception was significantly inhibited by naloxone, nor-BNI and naltrindole but not by beta-FNA or naloxonazine, implying involvement of kappa1- and delta-opioid mechanisms. When adrenergic and serotoninergic antagonists were used, yohimbine (P < 0.005) but not phentolamine or metergoline, decreased antinociception elicited by venlafaxine, implying a clear alpha2- and a minor alpha1-adrenergic mechanism of antinociception. When venlafaxine was administered together with various agonists of the opioid and alpha2- receptor subtypes, it significantly potentiated antinociception mediated by kappa1- kappa3- and delta-opioid receptor subtypes. The alpha2-adrenergic agonist clonidine significantly potentiated venlafaxine-mediated antinociception. Summing up these results, we conclude that the antinociceptive effect of venlafaxine is mainly influenced by the kappa- and delta-opioid receptor subtypes combined with the alpha2-adrenergic receptor. These results suggest a potential use of venlafaxine in the management of some pain syndromes. However, further research is needed in order to establish both the exact clinical indications and the effective doses of venlafaxine when prescribed for pain.

Metabolism of some "second"- and "fourth"-generation antidepressants: iprindole, viloxazine, bupropion, mianserin, maprotiline, trazodone, nefazodone, and venlafaxine

1. This review summarizes the major known aspects of the metabolism of second-generation (iprindole, viloxazine, bupropion, mianserin, maprotiline, and trazodone) and fourth-generation (nefazodone and venlafaxine) antidepressants. 2. Discussions about specific enzymes involved and about possible pharmacokinetic drug-drug interactions, particularly as they relate to cytochrome P450 enzymes, are provided.

Chirality and drugs used in psychiatry: nice to know or need to know?

1. Many drugs used to treat psychiatric disorders contain a chiral center or a center of unsaturation and are marketed as a mixture of the resultant enantiomers or geometric isomers, respectively. These enantiomers or geometric isomers may differ markedly with regard to their pharmacodynamic and/or pharmacokinetic properties. 2. Examples of the effects of chiral centers or geometric centers on such properties are given for drugs from the following classes: antidepressants (tricyclics, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, viloxazine, bupropion, trazodone, mianserin, venlaflaxine); benzodiazepines, zoplicone, and antipsychotics. 3. As described in this review, there are several notable examples of psychiatric drugs currently available where the individual enantiomers or geometric isomers differ considerably with regard to factors such as effects on amine transport systems, interactions with receptors and metabolizing enzymes, and clearance rates from the body. Indeed, relatively recent developments in analytical and preparative resolution of racemic and geometric drug mixtures and increased interest in developing new drugs which interact with specific targets, which have been described in detail at the molecular level, have resulted in increased emphasis on stereochemistry in drug development.

Systematic review and guide to selection of selective serotonin reuptake inhibitors

A meta-analysis of 20 short term comparative studies of 5 selective serotonin reuptake inhibitors (SSRIs; citalopram, fluoxetine, fluvoxamine, paroxetine and sertraline) has shown no difference in efficacy between individual compounds but a slower onset of action of fluoxetine. There were suggestions that fluoxetine caused more agitation, weight loss and dermatological reactions than the other SSRIs. More patients discontinued fluvoxamine and fewer patients stopped sertraline because of adverse effects than their comparator SSRIs. The most common adverse reactions to the SSRIs were gastrointestinal (especially nausea) and neuropsychiatric (particularly headache and tremor). Data from the Committee on Safety of Medicines showed more reports of suspected reactions (including discontinuation reactions) to paroxetine, and of gastrointestinal reactions to fluvoxamine and paroxetine, than the other SSRIs during their first 2 years of marketing. Prescription-event monitoring revealed a higher incidence of adverse events related to fluvoxamine than its comparators. There were higher incidences of gastrointestinal symptoms, malaise, sedation and tremor during treatment with fluvoxamine and of sedation, tremor, sweating, sexual dysfunction and discontinuation reactions with paroxetine. Fluoxetine was not associated with a higher incidence of suicidal, aggressive and related events than the other SSRIs. Patients have survived large overdoses of each of the compounds, but concern has been expressed over 6 fatalities following overdoses of citalopram. Drug interactions mediated by cytochrome P450 enzymes are theoretically less likely to occur during treatment with citalopram and sertraline, but there is a sparsity of clinical data to support this. Methodological difficulties and price changes do not allow choice for recommendations on the choice of SSRI based on pharmacoeconomic data. Taking into account the strengths and weaknesses of the methods used to compare drugs, guidelines to the selection of individual SSRIs in clinical practice are proposed. Citalopram should be avoided in patients likely to take overdoses. Fluoxetine may not be the drug of first choice for patients in whom a rapid antidepressant effect is important or for those who are agitated, but it may have advantages over other SSRIs in patients who are poorly compliant with treatment and those who have previously had troublesome discontinuation symptoms. Fluvoxamine, and possibly paroxetine, should not be used as first choice in patients especially prone to SSRI-related adverse reactions, while paroxetine should be avoided if previous discontinuation of treatment was troublesome. When in doubt about the risks of drug interactions, citalopram or sertraline should be considered given the lower theoretical risk of interactions.

Mechanisms of action and clinical characteristics of three atypical antidepressants: venlafaxine, nefazodone, bupropion

Tricyclic antidepressants have multiple sites of pharmacological actions which are responsible for their tolerability and toxicological problems as well as their efficacy. That fact has prompted the search for antidepressants with fewer sites of action. That search resulted in the serotonin selective reuptake inhibitors (SSRIs), with presumably only one site of action. Although the SSRIs are safer and better tolerated than the TCAs, a significant percentage of patients do not benefit from SSRIs. A group of "atypical antidepressants" including bupropion, nefazodone, and venlafaxine are known to have multiple sites of antidepressant action but do not interact at sites associated with side effects or tolerance. Thus this group of antidepressants present an important alternative to the SSRIs in the pharmacological therapy of depression. The basic pharmacological properties of bupropion, nefazodone, and venlafaxine are presented along with clinical profiles and the role of these three antidepressants in the pharmacotherapy of depression is discussed.

Absolute bioavailability and electroencephalographic effects of conventional and extended-release formulations of venlafaxine in healthy subjects

Venlafaxine is currently marketed for treatment of depressive disorders as a conventional tablet formulation with a twice or three times daily dosage regimen. The absolute bioavailability of the conventional (CF) and extended-release (XR) formulations and their effects on electroencephalograms (EEG) and on a visual analog scale (VAS) for nausea were assessed in a randomized, double-blind, four-way crossover, placebo-controlled study of 16 healthy young men who were given either a single oral dose of 50 mg of CF venlafaxine, 75 mg of XR venlafaxine, or an intravenous dose of 10 mg of venlafaxine, or a placebo at 1-week intervals. The absolute bioavailability of venlafaxine was between 40% and 45% and was similar for both the CF and XR formulations. Venlafaxine produced central effects of a desipramine-like antidepressant. Regardless of formulation tested, the main EEG changes were an increase in fast beta (20-30 Hz) energy, which was more pronounced over the frontotemporal regions and extended within the full beta range (16-40 Hz). Maximum effect was reached at 6 hours for the CF and reached a plateau from 10 to 24 hours for the XR formulation. A dose-proportional increase in central activity, expressed as area under the effect curve (AUE) of the beta band, was observed between the CF (50 mg) and XR (75 mg) formulations. Compared with the CF tablet, the XR formulation also produced a much less intense maximum effect and a decrease of 63% in the AUE of nausea normalized by dose. The XR formulation has the same absolute bioavailability and the same central activity as assessed by EEG, but produced less intensive nausea than CF venlafaxine. The present findings suggest that a once-daily dosage regimen should be sufficient. This was confirmed by several clinical trials in depressive patients.

Comparative efficacy and tolerability among different selective serotonin re-uptake inhibitors and venlafaxine in a naturalistic setting

The objective of this study was to compare, in a naturalistic setting, the efficacy and tolerability of currently available Selective Serotonin Reuptake Inhibitors (SSRIs) and venlafaxine in outpatients at a primary psychiatric care centre in Spain. The sample was composed of 194 patients with mood disorders (major depressive disorder or dysthymic disorder according to the DSM-TV criteria) who began treatment either with an SSRI (fluoxetine, fluvoxamine, paroxetine, sertraline, and citalopram) or with venlafaxine. Baseline severity of the mood disorder was assessed using the Hamilton Depression Rating Scale and State-Trait Anxiety Inventory, and therapeutic response was measured with the Clinical Global Impression for Therapeutic Improvement. Tolerability was assessed by recording spontaneously reported adverse experiences. There were no significant differences in the efficacy of the antidepressants under study, but there were differences in the incidence and profiles of adverse events. Fluoxetine was associated with the lowest incidence of adverse effects, in a logistical regression model, but particular events seemed to be associated with certain treatments: gastrointestinal discomfort (fluvoxamine), tremor (sertraline), dry mouth and dizziness (venlafaxine) and sweating and nervousness (citalopram). We conclude that in clinical practice there are differences in the tolerability of these antidepressants. Studies with bigger samples are needed to confirm these findings.

Effects of venlafaxine in the sleep architecture of rats

Different venlafaxine doses (1, 5, and 10 mg/kg) and saline solution were administered to ten male Wistar rats (Latin-Square design). Compared with saline, venlafaxine produced a dose-related suppression of REM sleep and an increase in wake time while slow wave sleep was reduced. This effect is similar to the one that has been reported with some tricyclic antidepressants.