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.

Concentrations of escitalopram in blood of patients treated in a naturalistic setting: focus on patients with alcohol and benzodiazepine use disorder.

The selective serotonin reuptake inhibitor escitalopram (ESC) is indicated for the treatment of major depressive disorder (MDD) and of generalized anxiety disorder (GAD). Monitoring of blood levels (BLs) is strongly indicated due to ESC's high interindividual pharmacokinetic variability. The aim of this study was to analyse clinical efficacy and pharmacokinetic influences on ESC BLs, in patients with depressive disorder alone and with comorbid alcohol or benzodiazepine use disorder. Data were collected from patients treated under naturalistic conditions for whom Therapeutic Drug Monitoring (TDM) was requested to guide antidepressant drug therapy and analysed retrospectively. Particular emphasis was given to patients with alcohol or benzodiazepine use disorder. Responders according to the clinical global impression (CGI) scale were compared with nonresponders for their ESC blood level (BL). The patient sample included 344 patients from 16 psychiatric hospitals in Germany. Influencing factors that could explain 22% of ESC BLs were dose, sex and age. Variability was high between individuals, and doses up to 40 mg were common in real-world settings. Patients treated with ESC monotherapy who responded showed a trend towards higher BLs compared to nonresponders with a concentration of 15 ng/mL separating both groups. Pathological changes in liver function (indicated by elevated GGT in combination with an AST/ALT ratio ≥ 1) resulted in higher dose-corrected ESC concentrations. Influencing factors that could explain 22% of ESC blood levels were dose, sex, and age. Our findings confirm the currently recommended lower threshold level and support the need for standard TDM analyses in everyday clinical practice. The ICD 10 diagnosis alcohol dependence alone does not lead to pharmacokinetic changes in the metabolism of ESC, but altered liver function does.