The relationship between dose and serotonin transporter occupancy of antidepressants-a systematic review

Selective Serotonin Reuptake Inhibitors for the Treatment of Depression in Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Although selective serotonin reuptake inhibitors (SSRIs) are usually considered safe to use in patients with Parkinson's disease (PD), there are mixed data about their effectiveness, and only a few investigations have led to a total improvement of depressive symptoms in patients with PD.

OBJECTIVES

We aimed to conduct a comprehensive systematic review and meta-analysis of all studies that investigated the effectiveness of SSRIs in treating depression in the context of PD.

METHODS

From its commencement to June 2024, the databases of MEDLINE via PubMed, Scopus, Embase, and Google Scholar were electronically searched for the relevant papers. All full-text journal articles assessing the effectiveness of SSRIs in treating depression in patients with PD were included. The tool developed by the Cochrane Collaboration was utilized to evaluate the bias risk. Data were analyzed utilizing a pair-wise comparison meta-analysis using the standardized mean difference.

RESULTS

A total of 19 articles and 22 separate interventions were included. We found that SSRI treatment attenuated depression in patients with PD (1.242 standardized mean difference, 95% confidence interval 0.956, 1.529, p < 0.001). The general heterogeneity of the studies was medium (ϰ2 = 72.818, T2 = 0.317, df = 21, I2 = 71.15%, p < 0.001). The funnel plot was reasonably symmetrical. However, three studies were trimmed to the left of the mean. Begg's test (p = 0.080), Egger's test (p = 0.121), and funnel plot showed no significant risk of publication bias. The meta-regression showed that the treatment effect increased as a function of paroxetine treatment duration (slope p = 0.001) but decreased as a function of sertraline treatment duration (slope p = 0.019).

CONCLUSIONS

There are few controlled antidepressant trials on the PD population, even though patients with PD frequently experience depression and use antidepressants. Clinical studies that are larger and better structured are needed in the future to determine if antidepressants are useful for treating patients with PD with depression.

Incidence of antidepressant discontinuation symptoms: a systematic review and meta-analysis

BACKGROUND

Antidepressant discontinuation symptoms are becoming an increasingly important part of clinical practice, but the incidence of antidepressant discontinuation symptoms has not been quantified. An estimate of antidepressant discontinuation symptoms incidence could inform patients and clinicians in the discontinuation of treatment, and provide useful information to researchers in antidepressant treatments. We aimed to assess the incidence of antidepressant discontinuation symptoms in patients discontinuing both antidepressants and placebo in the published literature.

METHODS

We systematically searched Medline, EMBASE, and CENTRAL from database inception until Oct 13, 2022 for randomised controlled trials (RCTs), other controlled trials, and observational studies assessing the incidence of antidepressant discontinuation symptoms. To be included, studies must have investigated cessation or tapering of an established antidepressant drug (excluding antipsychotics, lithium, or thyroxine) or placebo in participants with any mental, behavioural, or neurodevelopmental disorder. We excluded studies in neonates, and those using antidepressants for physical conditions such as pain syndromes due to organic disease. After study selection, summary data extraction, and risk of bias evaluation, data were pooled in random-effects meta-analyses. The main outcome was the incidence of antidepressant discontinuation symptoms after discontinuation of antidepressants or placebo. We also analysed the incidence of severe discontinuation symptoms. Sensitivity and meta-regression analyses tested a selection of methodological variables.

FINDINGS

From 6095 articles screened, 79 studies (44 RCTs and 35 observational studies) covering 21 002 patients were selected (72% female, 28% male, mean age 45 years [range 19·6-64·5]). Data on ethnicity were not consistently reported. 16 532 patients discontinued from an antidepressant, and 4470 patients discontinued from placebo. Incidence of at least one antidepressant discontinuation symptom was 0·31 (95% CI 0·27-0·35) in 62 study groups after discontinuation of antidepressants, and 0·17 (0·14-0·21) in 22 study groups after discontinuation of placebo. Between antidepressant and placebo groups of included RCTs, the summary difference in incidence was 0·08 [0·04-0·12]. The incidence of severe antidepressant discontinuation symptoms after discontinuation of an antidepressant was 0·028 (0·014-0·057) compared with 0·006 (0·002-0·013) after discontinuation of placebo. Desvenlafaxine, venlafaxine, imipramine, and escitalopram were associated with higher frequencies of discontinuation symptoms, and imipramine, paroxetine, and either desvenlafaxine or venlafaxine were associated with a higher severity of symptoms. Heterogeneity of results was substantial.

INTERPRETATION

Considering non-specific effects, as evidenced in placebo groups, the incidence of antidepressant discontinuation symptoms is approximately 15%, affecting one in six to seven patients who discontinue their medication. Subgroup analyses and heterogeneity figures point to factors not accounted for by diagnosis, medication, or trial-related characteristics, and might indicate subjective factors on the part of investigators, patients, or both. Residual or re-emerging psychopathology needs to be considered when interpreting the results, but our findings can inform clinicians and patients about the probable extent of antidepressant discontinuation symptoms without causing undue alarm.

FUNDING

None.

Allosteric modulation of serotonin and dopamine transporters: New insights from computations and experiments

Human monoamine transporters (MATs) are critical to regulating monoaminergic neurotransmission by translocating their substrates from the synaptic space back into the presynaptic neurons. As such, their primary substrate binding site S1 has been targeted by a wide range of compounds for treating neuropsychiatric and neurodegenerative disorders including depression, ADHD, neuropathic pain, and anxiety disorders. We present here a comparative study of the structural dynamics and ligand-binding properties of two MATs, dopamine transporter (DAT) and serotonin transporter (SERT), with focus on the allosteric modulation of their transport function by drugs or substrates that consistently bind a secondary site S2, proposed to serve as an allosteric site. Our systematic analysis of the conformational space and dynamics of a dataset of 50 structures resolved for DAT and SERT in the presence of one or more ligands/drugs reveals the specific residues playing a consistent role in coordinating the small molecules bound to subsites S2-I and S2-II within S2, such as R476 and Y481 in dDAT and E494, P561, and F556 in hSERT. Further analysis reveals how DAT and SERT differ in their two principal modes of structural changes, PC1 and PC2. Notably, PC1 underlies the transition between outward- and inward-facing states of the transporters as well as their gating; whereas PC2 supports the rearrangements of TM helices near the S2 site. Finally, the examination of cross-correlations between structural elements lining the respective sites S1 and S2 point to the crucial role of coupled motions between TM6a and TM10. In particular, we note the involvement of hSERT residues F335 and G338, and E493-E494-T497 belonging to these two respective helices, in establishing the allosteric communication between S1 and S2. These results help understand the molecular basis of the action of drugs that bind to the S2 site of DAT or SERT. They also provide a basis for designing allosteric modulators that may provide better control of specific interactions and cellular pathways, rather than indiscriminately inhibiting the transporter by targeting its orthosteric site.

Interventions to help patients withdraw from depression drugs: A systematic review

BACKGROUND

Depression drugs can be difficult to come off due to withdrawal symptoms. Gradual tapering with tapering support is needed to help patients withdraw safely.

OBJECTIVE

To review the withdrawal success rates, using any intervention, and the effects on relapse/recurrence rates, symptom severity, quality of life, and withdrawal symptoms.

METHODS

Systematic review based on PubMed and Embase searches (last search 4 October 2022) of randomised trials with one or more treatment arms aimed at helping patients withdraw from a depression drug, regardless of indication for treatment. We calculated the mean and median success rates and the risk difference of depressive relapse when discontinuing or continuing depression drugs.

RESULTS

We included 13 studies (2085 participants). Three compared two withdrawal interventions and ten compared drug discontinuation vs. continuation. The success rates varied hugely between the trials (9% to 80%), with a weighted mean of 47% (95% confidence interval 38% to 57%) and a median of 50% (interquartile range 29% to 65%). A meta-regression showed that the length of taper was highly predictive for the risk of relapse (P = 0.00001). All the studies we reviewed confounded withdrawal symptoms with relapse; did not use hyperbolic tapering; withdrew the depression drug too fast; and stopped it entirely when receptor occupancy was still high.

CONCLUSION

The true proportion of patients on depression drugs who can stop safely without relapse is likely considerably higher than the 50% we found.

Clinical benefits of vortioxetine 20 mg/day in patients with major depressive disorder

BACKGROUND

Vortioxetine has demonstrated dose-dependent efficacy in patients with major depressive disorder (MDD), with the greatest effect observed with vortioxetine 20 mg/day. This analysis further explored the clinical relevance of the more rapid and greater improvement in depressive symptoms observed with vortioxetine 20 mg/day vs 10 mg/day.

METHODS

Analysis of pooled data from six short-term (8-week), randomized, placebo-controlled, fixed-dose studies of vortioxetine 20 mg/day in patients with MDD (N = 2620). Symptomatic response (≥50% decrease in Montgomery-Åsberg Depression Rating Scale [MADRS] total score), sustained symptomatic response, and remission (MADRS total score ≤10) were assessed by vortioxetine dosage (20 or 10 mg/day).

RESULTS

After 8 weeks, 51.4% of patients receiving vortioxetine 20 mg/day had achieved symptomatic response vs 46.0% of those receiving vortioxetine 10 mg/day (P < .05). Significantly more patients achieved symptomatic response vs placebo from week 2 onwards for vortioxetine 20 mg/day and from week 6 onwards for vortioxetine 10 mg/day (both P ≤ .05). Sustained response was achieved from week 4 for 26.0% of patients receiving vortioxetine 20 mg/day vs 19.1% of those receiving vortioxetine 10 mg/day (P < .01), increasing to 36.0% and 29.8%, respectively, over the 8-week treatment period (P < .05). At week 8, 32.0% of patients receiving vortioxetine 20 mg/day were in remission vs 28.2% of those receiving vortioxetine 10 mg/day (P = .09). Rates of adverse events and treatment withdrawal were not increased during the week following vortioxetine dose up-titration to 20 mg/day.

CONCLUSION

Vortioxetine 20 mg/day provides more rapid and more sustained symptomatic response than vortioxetine 10 mg/day in patients with MDD, without compromising tolerability.

An assessment of the reporting of tapering methods in antidepressant discontinuation trials using the TIDieR checklist

BACKGROUND

The importance of tapering is increasingly recognised when discontinuing antidepressant medication. However, no previous studies have examined the reporting of antidepressant tapering methods in published studies.

AIM

The aim of this study was to assess the completeness of reporting of antidepressant tapering methods in a published systematic review using the Template for Intervention Description and Replication (TIDieR) checklist.

METHOD

A secondary analysis was conducted of studies included in a Cochrane systematic review that examined the effectiveness of approaches for discontinuing long-term antidepressant use. The completeness of reporting of antidepressant tapering methods in included studies was independently assessed by two researchers using the 12 items from the TIDieR checklist.

RESULTS

Twenty-two studies were included in the analysis. None of the study reports described all checklists items. No study clearly reported what materials had been provided (item 3) or whether tailoring had occurred (item 9). With the exception of providing a name for the intervention or study procedures (item 1), only a minority of studies clearly reported on any of the remaining checklist items.

CONCLUSION

The findings highlight a lack of detailed reporting of antidepressant tapering methods in published trials to date. This needs to be addressed as poor reporting could hinder replication and adaptation of existing interventions, as well as the potential for successful translation of effective tapering interventions into clinical practice.

Effects of escitalopram on synaptic density in the healthy human brain: a randomized controlled trial

Selective serotonin reuptake inhibitors (SSRIs) are widely used for treating neuropsychiatric disorders. However, the exact mechanism of action and why effects can take several weeks to manifest is not clear. The hypothesis of neuroplasticity is supported by preclinical studies, but the evidence in humans is limited. Here, we investigate the effects of the SSRI escitalopram on presynaptic density as a proxy for synaptic plasticity. In a double-blind placebo-controlled study (NCT04239339), 32 healthy participants with no history of psychiatric or cognitive disorders were randomized to receive daily oral dosing of either 20 mg escitalopram (n = 17) or a placebo (n = 15). After an intervention period of 3-5 weeks, participants underwent a [11C]UCB-J PET scan (29 with full arterial input function) to quantify synaptic vesicle glycoprotein 2A (SV2A) density in the hippocampus and the neocortex. Whereas we find no statistically significant group difference in SV2A binding after an average of 29 (range: 24-38) days of intervention, our secondary analyses show a time-dependent effect of escitalopram on cerebral SV2A binding with positive associations between [11C]UCB-J binding and duration of escitalopram intervention. Our findings suggest that brain synaptic plasticity evolves over 3-5 weeks in healthy humans following daily intake of escitalopram. This is the first in vivo evidence to support the hypothesis of neuroplasticity as a mechanism of action for SSRIs in humans and it offers a plausible biological explanation for the delayed treatment response commonly observed in patients treated with SSRIs. While replication is warranted, these results have important implications for the design of future clinical studies investigating the neurobiological effects of SSRIs.

Glutamatergic abnormalities in the pregenual anterior cingulate cortex in obsessive-compulsive disorder using magnetic resonance spectroscopy: A controlled study

In this study, we utilized proton magnetic resonance spectroscopy (MRS) to understand the role of glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA) of OCD patients in the pregenual anterior cingulate cortex (pgACC). In total, 54 patients with OCD and 54 healthy controls (HC) matched for age and sex were included in the study. They underwent MRS in the pgACC region to calculate the concentrations of Glu, Gln, GABA, and Glu + Gln (Glx). After quality control of the MRS data, 21 OCD and 21 HC were statistically analyzed. The severity of symptoms were evaluated using the Yale-Brown Obsessive-Compulsive Scale (YBOCS). In the statistical analysis, we compared differences between groups for the metabolites; in the OCD we analyzed the correlations with symptom severity, medication status, age, and duration of illness. A significant decrease in Glx, in Glu, and in Gln in the pgACC were observed in the OCD compared to HC. The correlation statistics showed a significant positive correlation between Glu levels and the YBOCS compulsions subscale. The results indicate that patients with OCD present a disturbance in glutamatergic metabolism in the pgACC. The results also demonstrate that these changes correlate with the severity of compulsions.

Evaluating lumateperone for its use in treating depressive episodes associated with bipolar I or II disorder in adults

INTRODUCTION

Lumateperone is a novel antipsychotic medication that has recently received approval by the United States Food and Drug Administration for treatment of major depressive episodes of type I and II bipolar disorder. It is approved for use as monotherapy or as an adjunctive treatment to lithium or valproic acid.

AREAS COVERED

Clinical trials performed with lumateperone for bipolar disorder were reviewed. Additionally, pharmacodynamic actions of lumateperone are reviewed. Lumateperone is superior to placebo whether used alone or in combination with a mood stabilizer in patients with type I or type II bipolar disorder. It achieves this effect with minimal dopamine blockade-related side effects due to less than 50% dopamine D2 receptor occupancy. While the pharmacodynamic profile of lumateperone is unique, the mechanism of action in bipolar depression remains obscure.

EXPERT OPINION

Lumateperone is an antipsychotic with full antagonist effects at the post-synaptic D2, and partial agonist effects at the presynaptic D2. This unique profile allows for both antipsychotic and antidepressant effects at the same dose, which does not produce dopamine-related side effects. Consequently, lumateperone is exceptionally well tolerated compared to other antidepressant-acting antipsychotic agents. It is now the only agent approved as an adjunct to the mood stabilizer for bipolar II depression.

Modeling outcome trajectories in patients with acquired brain injury using a non-linear dynamic evolution approach

This study describes a dynamic non-linear mathematical approach for modeling the course of disease in acquired brain injury (ABI) patients. Data from a multicentric study were used to evaluate the reliability of the Michaelis-Menten (MM) model applied to well-known clinical variables that assess the outcome of ABI patients. The sample consisted of 156 ABI patients admitted to eight neurorehabilitation subacute units and evaluated at baseline (T0), 4 months after the event (T1) and at discharge (T2). The MM model was used to characterize the trend of the first Principal Component Analysis (PCA) dimension (represented by the variables: feeding modality, RLAS, ERBI-A, Tracheostomy, CRS-r and ERBI-B) in order to predict the most plausible outcome, in terms of positive or negative Glasgow outcome score (GOS) at discharge. Exploring the evolution of the PCA dimension 1 over time, after day 86 the MM model better differentiated between the time course for individuals with a positive and negative GOS (accuracy: 85%; sensitivity: 90.6%; specificity: 62.5%). The non-linear dynamic mathematical model can be used to provide more comprehensive trajectories of the clinical evolution of ABI patients during the rehabilitation period. Our model can be used to address patients for interventions designed for a specific outcome trajectory.

Baseline platelet serotonin in a multi-site treatment study of depression in veterans administration patients: Distribution and effects of demographic variables and serotonin reuptake inhibitors

BACKGROUND

The objectives of the study were: (1) to examine the overall distribution of baseline platelet serotonin (5-hydroxytryptamine, 5-HT) values in patients seeking treatment for depression and to define subgroups based on the apparent presence or absence of drug exposure; (2) to assess the bioeffect of 5-HT reuptake inhibitors (SRIs) at the platelet 5-HT transporter; and (3) to examine the relationships of demographic variables including population (ancestry), sex, age, and season of sampling to platelet 5-HT concentration.

METHODS

Platelet 5-HT levels were measured in a cross-sectional study of 1433 Veterans Administration (VA) patients participating in a pragmatic multi-site pharmacogenomic treatment study of depression. Patients were characterized medically and demographically using VA health records and self-report.

RESULTS

A clearly bimodal distribution was observed for platelet 5-HT levels with the lower mode associated with patients exposed to SRIs at baseline. Median transporter blockade bioeffects were similar across the various selective 5-HT reuptake inhibitors (SSRIs) and 5-HT/norepinephrine reuptake inhibitors (SNRIs). In a subset of patients apparently not exposed to an SRI, significant effects of population and sex were observed with group mean platelet 5-HT levels being 25 % greater (p < 0.001) in African-American (AA) individuals compared to European-Americans (EAs). The female group mean was 14 % (p < 0.001) greater than male group mean. An effect of age was observed (r = -0.11, p < 0.001) and no effect of season or month of sampling was seen.

CONCLUSIONS

Further research is warranted to understand the bases and clinical implications of the population and sex differences. The apparent similarity in bioeffect at the 5-HT transporter across SSRIs and when comparing SSRIs and SNRIs informs discussions about initiating, dose adjustment and switching of 5-HT reuptake inhibitors.

Systematic review of studies using platelet serotonin content to assess bioeffect of serotonin reuptake inhibitors at the serotonin transporter

RATIONALE

Assessment of the bioeffect of serotonin reuptake inhibitors (SRIs, including both selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs)) at the serotonin transporter (SERT) in patients and healthy controls can have important theoretical and clinical implications.

OBJECTIVES

Bioeffect at SERT has been assessed by neuroimaging of brain SERT occupancy, through in vitro measurements of platelet serotonin (5-HT) uptake, and by measuring platelet 5-HT content pre- and post-initiation of SRI administration. Studies of platelet 5-HT content were reviewed in order to (1) determine the overall apparent bioeffect of SRIs; (2) compare bioeffect across types of SRIs; (3) compare the three approaches to assessing SRI bioeffect; and (4) determine how the findings might inform clinical practice.

METHODS

We performed a systematic review of the published studies that measured platelet 5-HT content to assess SRI bioeffect at the platelet SERT. Studies using neuroimaging and in vitro platelet 5-HT uptake to assess SRI bioeffect were reviewed for comparison purposes.

RESULTS

Clinical doses of SRIs typically resulted in 70-90% reductions in platelet 5-HT content. The observed bioeffect at the platelet SERT appeared similar among different SSRIs and SNRIs. The bioeffect estimations based on platelet 5-HT content were consistent with those obtained using neuroimaging to assess brain SERT occupancy and those based on the in vitro measurement of platelet 5-HT uptake.

CONCLUSIONS

In general, excellent agreement was seen in the apparent SRI bioeffect (70-90% inhibition) among the platelet 5-HT content studies and across the three bioeffect approaches. Theoretical and practical clinical implications are discussed.

Future Prospects of Positron Emission Tomography–Magnetic Resonance Imaging Hybrid Systems and Applications in Psychiatric Disorders

A positron emission tomography (PET)–magnetic resonance imaging (MRI) hybrid system has been developed to improve the accuracy of molecular imaging with structural imaging. However, the mismatch in spatial resolution between the two systems hinders the use of the hybrid system. As the magnetic field of the MRI increased up to 7.0 tesla in the commercial system, the performance of the MRI system largely improved. Several technical attempts in terms of the detector and the software used with the PET were made to improve the performance. As a result, the high resolution of the PET–MRI fusion system enables quantitation of metabolism and molecular information in the small substructures of the brainstem, hippocampus, and thalamus. Many studies on psychiatric disorders, which are difficult to diagnose with medical imaging, have been accomplished using various radioligands, but only a few studies have been conducted using the PET–MRI fusion system. To increase the clinical usefulness of medical imaging in psychiatric disorders, a high-resolution PET–MRI fusion system can play a key role by providing important information on both molecular and structural aspects in the fine structures of the brain. The development of high-resolution PET–MR systems and their potential roles in clinical studies of psychiatric disorders were reviewed as prospective views in future diagnostics.

[Stopping antidepressants: withdrawal symptoms and rebound effects : Review and practical recommendations]

Stopping antidepressants can cause withdrawal (discontinuation) symptoms, the return of the original illness, and rebound. The latter means that the disease will return stronger, faster, or with greater likelihood than if it had not been treated with medication. The Psychiatry Working Group of the Drug Commission of the German Medical Association (AkdÄ) presents the scientific findings and provides practical recommendations for action. Withdrawal symptoms are multiform; unspecific physical symptoms are predominant. Distinguishing them from the recurrence of depressive symptoms can be difficult. Most of them are mild and self-limiting. There is insufficient evidence on the extent and frequency of rebound depression. The rebound risk implies that when establishing the medication, the short-term benefit must be weighed against the possible long-term risk of chronic depression or the possible need for long-term medication. Patients should be informed about the risk of withdrawal both as early as the joint decision-making process about treatment initiation and regularly during the course of treatment. Withdrawal should take place gradually, except in emergency situations, whereby small steps should be taken, especially in the low-dose range.

Dose-response effects of selective serotonin reuptake inhibitor monotherapy for the treatment of depression: systematic review of reviews and meta-narrative synthesis

Objective

To assess and clarify the relations between selective serotonin reuptake inhibitor (SSRI) dose efficacy, acceptability (early treatment discontinuation (dropouts)), and tolerability (reported adverse drug effects), and critically evaluate methods previously used to examine SSRI dose-response effects for the treatment of depression in adults.

Design

Systematic review of reviews and meta-narrative synthesis.

Data sources

Embase, Medline, PsycINFO, Scopus, and the Cochrane Collaboration library, from 1975 to December 2021. Reference lists of national depression treatment guidelines were systemically searched by hand.

Eligibility criteria for selecting studies

Reviews assessing SSRI monotherapy dose-response effects for the treatment of depression in adults (age ≥18 years) reporting efficacy, acceptability, or tolerability. Reviews meeting inclusion criteria had a high degree of heterogeneity, due to methodological diversity; therefore, a meta-narrative synthesis approach was applied. Standard daily doses were defined as 20 mg citalopram, fluoxetine, paroxetine; 50 mg sertraline; and 10 mg escitalopram. Risk of bias was assessed using the Risk of Bias in Systematic Reviews tool, in line with Cochrane recommendations.

Results

The search identified 9138 records; 387 full text reports were assessed for eligibility, 42 of which matched the inclusion criteria. The majority, 83% (n=35), of reviews included data for studies with a duration of ≤12 weeks (ie, the acute phase of depression treatment). Of 39 reviews assessing efficacy, the majority (n=26) indicated that individual SSRIs and SSRI class demonstrated flat dose-response effects; standard doses were optimal for efficacy. Acceptability or tolerability were assessed in 28 reviews. Higher than standard daily doses were associated with higher dropout rates and a greater incidence of adverse drug effects (eg, nausea, sexual dysfunction, fatigue, anxiety). Despite a range of methods being reported, there was an overall consensus regarding SSRI dose related efficacy, dropouts, and adverse drug effects.

Conclusion

Standard daily doses of SSRIs for the treatment of depression in adults provide a favourable balance between efficacy, acceptability, and tolerability. Patients are encouraged to talk to their prescriber or community pharmacist if they experience adverse effects or have any concerns about their drug treatments.

ABCB1 variants and sex affect serotonin transporter occupancy in the brain

Strategies to personalize psychopharmacological treatment promise to improve efficacy and tolerability. We measured serotonin transporter occupancy immediately after infusion of the widely prescribed P-glycoprotein substrate citalopram and assessed to what extent variants of the ABCB1 gene affect drug target engagement in the brain in vivo. A total of 79 participants (39 female) including 31 patients with major depression and 48 healthy volunteers underwent two PET/MRI scans with the tracer [¹¹C]DASB and placebo-controlled infusion of citalopram (8 mg) in a cross-over design. We tested the effect of six ABCB1 single nucleotide polymorphisms and found lower SERT occupancy in ABCB1 rs2235015 minor allele carriers (n = 26, MAF = 0.18) compared to major allele homozygotes (t₇₃ = 2.73, p_FWE < 0.05) as well as in men compared to women (t₇₃ = 3.33, p_FWE < 0.05). These effects were robust to correction for citalopram plasma concentration, age and diagnosis. From occupancy we derived the ratio of occupied to unoccupied SERT, because in theory this measure is equal to the product of drug affinity and concentration at target sites. A model combining genotype with basic clinical variables, predicted that, at the same dosage, occupied to unoccupied SERT ratio was -14.48 ± 5.38% lower in rs2235015 minor allele carriers, +19.10 ± 6.95% higher in women, -4.83 ± 2.70% lower per 10 kg bodyweight, and -2.68 ± 3.07% lower per 10 years of age. Our results support the exploration of clinical algorithms with adjustment of initial citalopram dosing and highlight the potential of imaging-genetics for precision pharmacotherapy in psychiatry.

Clinical practice guideline recommendations on tapering and discontinuing antidepressants for depression: a systematic review

BACKGROUND

Tapering and discontinuing antidepressants are important aspects of the management of patients with depression and should therefore be considered in clinical practice guidelines.

OBJECTIVES

We aimed to assess the extent and content, and appraise the quality, of guidance on tapering and discontinuing antidepressants in major clinical practice guidelines on depression.

METHODS

Systematic review of clinical practice guidelines on depression issued by national health authorities and major national or international professional organisations in the United Kingdom, the United States, Canada, Australia, Singapore, Ireland and New Zealand (PROSPERO CRD42020220682). We searched PubMed, 14 guideline registries and the websites of relevant organisations (last search 25 May 2021). The clinical practice guidelines were assessed for recommendations and information relevant to tapering and discontinuing antidepressants. The quality of the clinical practice guidelines as they pertained to tapering and discontinuation was assessed using the AGREE II tool.

RESULTS

Of the 21 included clinical practice guidelines, 15 (71%) recommended that antidepressants are tapered gradually or slowly, but none provided guidance on dose reductions, how to distinguish withdrawal symptoms from relapse or how to manage withdrawal symptoms. Psychological challenges were not addressed in any clinical practice guideline, and the treatment algorithms and flow charts did not include discontinuation. The quality of the clinical practice guidelines was overall low.

CONCLUSION

Current major clinical practice guidelines provide little support for clinicians wishing to help patients discontinue or taper antidepressants in terms of mitigating and managing withdrawal symptoms. Patients who have deteriorated upon following current guidance on tapering and discontinuing antidepressants thus cannot be concluded to have experienced a relapse. Better guidance requires better randomised trials investigating interventions for discontinuing or tapering antidepressants.