Venlafaxine's therapeutic reference range in the treatment of depression revised: a systematic review and meta-analysis

INTRODUCTION

The selective serotonin and norepinephrine reuptake inhibitor venlafaxine is among the most prescribed antidepressant drugs worldwide and, according to guidelines, its dose titration should be guided by drug-level monitoring of its active moiety (AM) which consists of venlafaxine (VEN) plus active metabolite O-desmethylvenlafaxine (ODV). This indication of therapeutic drug monitoring (TDM), however, assumes a clear concentration/effect relationship for a drug, which for VEN has not been systematically explored yet.

OBJECTIVES

We performed a systematic review and meta-analysis to investigate the relationship between blood levels, efficacy, and adverse reactions in order to suggest an optimal target concentration range for VEN oral formulations for the treatment of depression.

METHODS

Four databases (MEDLINE (PubMed), PsycINFO, Web of Science Core Collection, and Cochrane Library) were systematically searched in March 2022 for relevant articles according to a previously published protocol. Reviewers independently screened references and performed data extraction and critical appraisal.

RESULTS

High-quality randomized controlled trials investigating concentration/efficacy relationships and studies using a placebo lead-in phase were not found. Sixty-eight articles, consisting mostly of naturalistic TDM studies or small noncontrolled studies, met the eligibility criteria. Of them, five cohort studies reported a positive correlation between blood levels and antidepressant effects after VEN treatment. Our meta-analyses showed (i) higher AM and (ii) higher ODV concentrations in patients responding to VEN treatment when compared to non-responders (n = 360, k = 5). AM concentration-dependent occurrence of tremor was reported in one study. We found a linear relationship between daily dose and AM concentration within guideline recommended doses (75-225 mg/day). The population-based concentration ranges (25-75% interquartile) among 11 studies (n = 3200) using flexible dosing were (i) 225-450 ng/ml for the AM and (ii) 144-302 ng/ml for ODV. One PET study reported an occupancy of 80% serotonin transporters for ODV serum levels above 85 ng/ml. Based on our findings, we propose a therapeutic reference range for AM of 140-600 ng/ml.

CONCLUSION

VEN TDM within a range of 140 to 600 ng/ml (AM) will increase the probability of response in nonresponders. A titration within the proposed reference range is recommended in case of non-response at lower drug concentrations as a consequence of VEN's dual mechanism of action via combined serotonin and norepinephrine reuptake inhibition. Drug titration towards higher concentrations will, however, increase the risk for ADRs, in particular with supratherapeutic drug concentrations.

Tools for optimising pharmacotherapy in psychiatry (therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests): focus on antidepressants

Objectives: More than 40 drugs are available to treat affective disorders. Individual selection of the optimal drug and dose is required to attain the highest possible efficacy and acceptable tolerability for every patient.Methods: This review, which includes more than 500 articles selected by 30 experts, combines relevant knowledge on studies investigating the pharmacokinetics, pharmacodynamics and pharmacogenetics of 33 antidepressant drugs and of 4 drugs approved for augmentation in cases of insufficient response to antidepressant monotherapy. Such studies typically measure drug concentrations in blood (i.e. therapeutic drug monitoring) and genotype relevant genetic polymorphisms of enzymes, transporters or receptors involved in drug metabolism or mechanism of action. Imaging studies, primarily positron emission tomography that relates drug concentrations in blood and radioligand binding, are considered to quantify target structure occupancy by the antidepressant drugs in vivo. Results: Evidence is given that in vivo imaging, therapeutic drug monitoring and genotyping and/or phenotyping of drug metabolising enzymes should be an integral part in the development of any new antidepressant drug.Conclusions: To guide antidepressant drug therapy in everyday practice, there are multiple indications such as uncertain adherence, polypharmacy, nonresponse and/or adverse reactions under therapeutically recommended doses, where therapeutic drug monitoring and cytochrome P450 genotyping and/or phenotyping should be applied as valid tools of precision medicine.

Clinical applications of single photon emission tomography in neuromedicine

This article gives in his second part a critical review of the clinical applications of SPECT with perfusion markers and receptor ligands in dementing disorders and psychosis. In addition this review discusses clinical applications of SPECT investigations with perfusion markers in inflammatory diseases of the central nervous system and in brain trauma.

Clinical applications of single photon emission tomography in neuromedicine

Single photon emission tomography is, because of its availability and the relatively low costs, the functional imaging modality currently most widely used for clinical applications in the brain. Beside the application of radiopharmaceuticals for the assessment of regional cerebral blood flow there is an increasing clinical use of more selective SPECT-radiopharmaceuticals, like amino acid analogs or receptor ligands. This article gives in his first part a critical review of the clinical applications of SPECT in neuro-oncology, epilepsy, basal ganglia disorders and cerebrovascular disease.

Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology: Update 2017

Therapeutic drug monitoring (TDM) is the quantification and interpretation of drug concentrations in blood to optimize pharmacotherapy. It considers the interindividual variability of pharmacokinetics and thus enables personalized pharmacotherapy. In psychiatry and neurology, patient populations that may particularly benefit from TDM are children and adolescents, pregnant women, elderly patients, individuals with intellectual disabilities, patients with substance abuse disorders, forensic psychiatric patients or patients with known or suspected pharmacokinetic abnormalities. Non-response at therapeutic doses, uncertain drug adherence, suboptimal tolerability, or pharmacokinetic drug-drug interactions are typical indications for TDM. However, the potential benefits of TDM to optimize pharmacotherapy can only be obtained if the method is adequately integrated in the clinical treatment process. To supply treating physicians and laboratories with valid information on TDM, the TDM task force of the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP) issued their first guidelines for TDM in psychiatry in 2004. After an update in 2011, it was time for the next update. Following the new guidelines holds the potential to improve neuropsychopharmacotherapy, accelerate the recovery of many patients, and reduce health care costs.

Neural correlates of naturalistic social cognition: brain-behavior relationships in healthy adults

Being able to infer the thoughts, feelings and intentions of those around us is indispensable in order to function in a social world. Despite growing interest in social cognition and its neural underpinnings, the factors that contribute to successful mental state attribution remain unclear. Current knowledge is limited because the most widely used tasks suffer from two main constraints: (i) They fail to capture individual variability due to ceiling effects and (ii) they use highly simplistic, often artificial stimuli inapt to mirror real-world socio-cognitive demands. In the present study, we address these problems by employing complex depictions of naturalistic social interactions that vary in both valence (positive vs negative) and ambiguity (high vs low). Thirty-eight healthy participants (20 female) made mental state judgments while brain responses were obtained using functional magnetic resonance imaging (fMRI). Accuracy varied based on valence and ambiguity conditions and women were more accurate than men with highly ambiguous social stimuli. Activity of the orbitofrontal cortex predicted performance in the high ambiguity condition. The results shed light on subtle differences in mentalizing abilities and associated neural activity.

Association of Common Polymorphisms in the Nicotinic Acetylcholine Receptor Alpha4 Subunit Gene with an Electrophysiological Endophenotype in a Large Population-Based Sample

Variation in genes coding for nicotinic acetylcholine receptor (nAChR) subunits affect cognitive processes and may contribute to the genetic architecture of neuropsychiatric disorders. Single nucleotide polymorphisms (SNPs) in the CHRNA4 gene that codes for the alpha4 subunit of alpha4/beta2-containing receptors have previously been implicated in aspects of (mostly visual) attention and smoking-related behavioral measures. Here we investigated the effects of six synonymous but functional CHRNA4 exon 5 SNPs on the N100 event-related potential (ERP), an electrophysiological endophenotype elicited by a standard auditory oddball. A total of N = 1,705 subjects randomly selected from the general population were studied with electroencephalography (EEG) as part of the German Multicenter Study on nicotine addiction. Two of the six variants, rs1044396 and neighboring rs1044397, were significantly associated with N100 amplitude. This effect was pronounced in females where we also observed an effect on reaction time. Sequencing of the complete exon 5 region in the population sample excluded the existence of additional/functional variants that may be responsible for the observed effects. This is the first large-scale population-based study investigation the effects of CHRNA4 SNPs on brain activity measures related to stimulus processing and attention. Our results provide further evidence that common synonymous CHRNA4 exon 5 SNPs affect cognitive processes and suggest that they also play a role in the auditory system. As N100 amplitude reduction is considered a schizophrenia-related endophenotype the SNPs studied here may also be associated with schizophrenia outcome measures.

[Significance of the German Act on the Reform of the Market for Medicinal Products for psychopharmacotherapy]

The German Act on the Reform of the Market for Medicinal Products (AMNOG) will lead to rapid disappearance of many new psychotropic drugs from the market in Germany over the next few years or their not being introduced in the first place. This article lists the reasons and discusses possible solutions. In the long term, the AMNOG could not only lead to an improvement of psychopharmacology but also contribute to the development of psychiatry as a whole, especially if its standards become an international reference.

[Antidepressive agents and suicidal tendencies]

In the last 2 years the discussions on the question whether antidepressants, especially selective serotonin reuptake inhibitors (SSRIs) can lead to suicidality, aggression and violence, flared up again. The available data on the problem, which has been discussed since the introduction of this substance group in the late 1980s, is presented in this article. A systematic literature search showed that a scientific consensus exists that the benefits of antidepressant pharmacotherapy in general, and of treatment with SSRIs and selective serotonin/norepinephrine reuptake inhibitors (SSNRIs) in particular, outweigh the risks of their use. This also applies to the treatment of children, adolescents and young adults. The agitation occasionally occurring at the beginning of treatment, which can be experienced as aversive in susceptible patients, can intensify or even trigger suicidal thoughts or impulses. This has to be paid particular attention to especially at the beginning of treatment. It is recommended that the indications for antidepressant pharmacotherapy of children, adolescents and young adults are assessed by a specialist.

[Neuroenhancement]

BACKGROUND

Cognitive enhancement or neuroenhancement describes the increase in cognitive performance in humans by means of psychotropic drugs or brain stimulation methods, such as transcranial magnetic stimulation (TMS).

PROBLEM

This article discusses the potential of pharmacological cognitive enhancement with some of the most common drugs.

METHODS

A selective literature search was performed taking into account the most important groups of substances (i.e. caffeine, nicotine, stimulants including modafinil, and acetylcholine esterase inhibitors) for which studies on the pharmacological elevation of cognitive performance in healthy subjects are available.

RESULTS

The extent of the effects that can be pharmacologically achieved is essentially genetically determined. Some of the best-characterized polymorphisms are described here. Pharmacological enhancement of cognitive performance is currently possible with all of the compounds described here and caffeine and nicotine are used by millions of people without the explicit intention of most consumers of cognitive enhancement.

DISCUSSION

Clinical neuroscientists are required to share their expertise to a greater extent in the social discourse on cognitive enhancement in the future in order to influence opinion-forming and decision-making processes.

Dopamine-modulated aversive emotion processing fails in alcohol-dependent patients

Negative mood states after alcohol detoxification may enhance the relapse risk. As recently shown in healthy volunteers, dopamine storage capacity (V d) in the left amygdala was positively correlated with functional activation in the left amygdala and anterior cingulate cortex (ACC) during an emotional task; high functional connectivity between the amygdala and the ACC, a region important for emotion regulation, was associated with low trait anxiety. Based on these findings, we now tested whether detoxified alcohol-dependent patients have a disrupted modulation of the anterior cingulate cortex activation in response to aversive stimuli by amygdala dopamine. Furthermore, we asked whether disrupted functional coupling between amygdala and ACC during aversive processing is related to trait anxiety.We used combined 6-[18F]-fluoro-l-DOPA positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and Spielberger's state-trait anxiety questionnaire (STAI) in 11 male detoxified alcohol-dependent patients compared to 13 matched healthy controls.Unlike healthy controls, patients showed no significant correlation between our PET metric for dopamine storage capacity (FDOPA V d), in left amygdala and activation in left ACC. Moreover, the functional connectivity between amygdala and ACC during processing of aversive emotional stimuli was reduced in patients. Voxel-based morphometry did not reveal any discernible group differences in amygdala volume.These results suggest that dopamine-modulated corticolimbic circuit function is important for responding to emotional information such that apparent functional deficits in this neuromodulatory circuitry may contribute to trait anxiety in alcohol-dependent patients.

Oxytocin plasma concentrations after single intranasal oxytocin administration - a study in healthy men

The neuropeptide oxytocin has become a subject of great interest in studies investigating human social cognition. Single intranasal administration of the hormone has been reported to have positive behavioral effects, such as increasing trust or facilitating social approach, 45-80 min after administration. However, little is still known about the long-term pharmacokinetics of oxytocin nasal spray application in humans. This study addressed the question how long oxytocin plasma levels remain elevated following nasal spray administration. Another goal was to examine the influence of oxytocin administration on endogenous steroid hormones since such alterations might modulate social behavior via an indirect way. Eight healthy Caucasian men were challenged with a single intranasal application of 26 international units of oxytocin. Changes in oxytocin blood plasma levels, as well as steroid hormone levels of progesterone, testosterone and estradiol were assessed at 5 consecutive time points over a period of 3.5 h (-5, +30, +90, +150, +210 min relative to oxytocin administration). Results gave evidence for a substantial rise of oxytocin plasma levels 30 min after intranasal administration, observed in 7 of 8 participants. Group mean oxytocin plasma level was found to have returned to baseline already 90 min post administration, though in some individuals the plasma levels was still elevated relative to sampling at post 150 min. Steroid hormone analyses yielded a slight augmentation of endogenous testosterone levels 210 min after oxytocin administration. Our data confirms previous findings that oxytocin administered as a nasal spray enters the blood circulation, elevating oxytocin plasma levels for a limited time. Our findings suggest that this time window differs between individuals, but that, for the used dose, it does not extend beyond 150 min post administration. The data further provides preliminary evidence that intranasal oxytocin has an enhancing effect on testosterone in healthy men.