Antidepressant Selection for Major Depressive Disorder (MDD)
For adults with MDD, antidepressant effectiveness is generally comparable across antidepressant classes, with initial selection driven primarily by tolerability, safety, side effects, drug–drug interactions, and patient preference [1]. SSRIs are recommended as the first choice for most people in NICE guidance, with treatment choice tailored to medication effects and individual risk factors [2].
Medication Classification and Core Effects
Escitalopram is an SSRI (selective serotonin reuptake inhibitor) [1]. Mirtazapine is an antidepressant in the “other antidepressant” group and is pharmacologically distinct from SSRIs [1]. Clinical selection should consider the differing adverse-effect profiles across agents, including sedation and weight gain [1].
Medication Selection Algorithm
Key selection factors supported by APA guidance include [1]:
- Patient preference [1]
- Prior response or lack of response to antidepressants [1]
- Safety, tolerability, and anticipated side effects [1]
- Co-occurring psychiatric or general medical conditions [1]
- Potential drug interactions [1]
- Medication half-life [1]
- Cost [1]
Relative Efficacy Evidence
APA guidance states that antidepressant effectiveness is generally comparable between classes and within classes, with similar response ranges reported in clinical trials [1]. NICE guidance supports treatment selection based on side-effect profile and patient factors rather than on a strong expectation of large efficacy differences between standard antidepressants [2].
Monotherapy Versus Combination Therapy
NICE guidance includes combination therapy strategies when monotherapy plus psychological therapy has limited response, with options that may include adding mirtazapine to an SSRI as an example of adding an antidepressant from a different class [2]. NICE guidance highlights that combination approaches can increase side-effect burden and require shared decision-making about risks [2].
Important Safety and Monitoring Nuances
NICE guidance recommends ECG monitoring at baseline and when final dose is reached for people with established cardiovascular disease or specific cardiovascular risk (for example, high blood pressure) and for those taking other medicines known to prolong QT interval, including escitalopram [2]. NICE guidance emphasizes monitoring for adverse effects at each review, including extrapyramidal effects and prolactin-related side effects for relevant augmentation or comedications, and dose reduction when needed [2].
Initiation Thresholds and Treatment Escalation
NICE guidance defines “less severe depression” as PHQ-9 scoring less than 16 and includes active monitoring options for people who do not want immediate treatment [2]. For people with more severe depression, pharmacologic treatment strategies are integrated with psychological therapy and follow-up monitoring within the NICE algorithm [2]. For inadequate response, NICE guidance supports escalation through dose increase, switching antidepressants, or augmentation/combination strategies depending on preferences and clinical need [2].
Common Pitfalls to Avoid
NICE guidance advises discussing possible increased side-effect burden when combination treatment is considered [2]. APA guidance emphasizes that medication choice should account for tolerability, safety, side effects, and drug interactions, since antidepressants differ in these properties [1].
Targets of Therapy and Ongoing Assessment
NICE guidance emphasizes shared decision-making and monitoring of treatment effects and tolerability during follow-up visits [2]. APA guidance supports selecting antidepressant regimens based on tolerability and side effects to improve the likelihood of successful continuation and adequate trial completion [1].