Pharmacology · CNS

Treatment Algorithms, Augmentation, and TRD

Module 8 — Chapter 17: Antidepressant Drugs

The STAR*D step flow is the central clinical reference for understanding why treatment-resistant depression is so common: remission rates fall sharply at each successive step — approximately 37% at Step 1, 31% at Step 2, 14% at Step 3, and 13% at Step 4 — meaning that only about one-third of patients achieve remission on the first antidepressant tried, and cumulative remission across all four steps reaches only around 67%.
Treatment-resistant depression is defined as failure of two adequate trials (four to six weeks at therapeutic dose); the augmentation table shows the options at this decision point — atypical antipsychotics (aripiprazole, quetiapine, brexpiprazole) have the strongest evidence base (FDA-approved augmentation indications), followed by lithium and thyroid hormone (T3), which have older evidence and are still used when antipsychotics are not tolerated.
The bipolar trap is a critical clinical mistake the infographic highlights: starting an antidepressant in unrecognized bipolar disorder can precipitate a manic episode or rapid cycling; screening with a mood history before prescribing — asking about prior periods of decreased sleep need, grandiosity, and impulsivity — is essential, and mood stabilizer monotherapy is preferred over antidepressants when bipolar is confirmed.
Duration of therapy follows episode-count rules: the first depressive episode warrants six to nine months of continuation after remission; a second episode warrants one to two years; three or more episodes strongly supports indefinite maintenance therapy, since the relapse risk approaches 90% in patients with recurrent depression who stop treatment.
Somatic treatments complement pharmacotherapy when medication fails: ECT remains the most effective acute treatment for severe, psychotic, or medication-refractory depression with response rates of 60 to 80%; repetitive transcranial magnetic stimulation is FDA-cleared for treatment-resistant depression with a more favorable adverse effect profile; both can be used alongside ongoing pharmacotherapy.

Abbreviations: TRD = treatment-resistant depression · STAR*D = Sequenced Treatment Alternatives to Relieve Depression · SSRI = selective serotonin reuptake inhibitor · SNRI = serotonin-norepinephrine reuptake inhibitor · TCA = tricyclic antidepressant · MAOI = monoamine oxidase inhibitor · AAP = atypical antipsychotic · T3 = triiodothyronine · ECT = electroconvulsive therapy · rTMS = repetitive transcranial magnetic stimulation · PHQ-9 = Patient Health Questionnaire-9 · MADRS = Montgomery-Asberg Depression Rating Scale

STAR*D Stepwise Algorithm — Remission Rates at Each Step

First-Line Antidepressant

SSRI (citalopram in STAR*D); adequate trial = 4–6 weeks at therapeutic dose

Remission rate: ~37%

Switch or Augment

Switch to different class (SNRI, bupropion, mirtazapine) OR augment (buspirone, bupropion, lithium)

Remission rate: ~31%

Augment or Switch Again

Add lithium or T3 to current agent; or switch to TCA or SNRI; consider referral

Remission rate: ~14%

MAOI or Combination

Tranylcypromine or mirtazapine plus venlafaxine combination; specialist management

Remission rate: ~13%

Augmentation Strategies for Treatment-Resistant Depression

Agent	Evidence Level	Key Notes
Aripiprazole + antidepressant	FDA-approved augmentation	2–15 mg/day; akathisia most common; metabolic monitoring
Quetiapine XR + antidepressant	FDA-approved augmentation	150–300 mg/day; sedation, weight gain; also approved for MDD monotherapy at lower doses
Brexpiprazole + antidepressant	FDA-approved augmentation	1–3 mg/day; akathisia less than aripiprazole; metabolic monitoring
Lithium + antidepressant	Strong (older evidence)	Target level 0.6–1.0 mEq/L; narrow therapeutic index; thyroid and renal monitoring; serotonin syndrome risk with MAOIs
Triiodothyronine (T3)	Moderate	25–50 mcg/day; used when lithium not tolerated; tachycardia, weight loss, anxiety
Buspirone + SSRI	Modest (mixed results)	5-HT1A partial agonist; safe; some anxiolytic benefit; not consistently effective as antidepressant augmentation

Somatic Treatments and Duration Rules

Non-Pharmacological Options

ECT and rTMS

ECT: most effective for severe, psychotic, or medication-refractory depression; response rate 60–80%; fastest onset; can be used in pregnancy; memory side effects (usually temporary)
rTMS: FDA-cleared for TRD; high-frequency stimulation of left dorsolateral prefrontal cortex; no anesthesia needed; headache most common; 4–6 week course
Both can be combined with pharmacotherapy
Ketamine/esketamine: rapid bridge to response while antidepressants take effect

Continuation and Maintenance

Duration of Therapy Rules

First episode: continue 6–9 months after remission
Second episode: continue 1–2 years after remission
Three or more episodes: indefinite maintenance therapy
Relapse risk without maintenance: ~50% within 6 months; ~90% lifetime with recurrent depression
Measurement-based care: PHQ-9 or MADRS at each visit to track response objectively

The Bipolar Trap

Antidepressants can precipitate mania, hypomania, or rapid cycling in patients with unrecognized bipolar disorder. Screen for prior manic/hypomanic episodes before prescribing any antidepressant. If bipolar disorder is identified, mood stabilizer monotherapy (lithium, valproate, lamotrigine) is preferred — antidepressants are used only as adjuncts and with caution, if at all.

Suggested References

Author / Organization	Title	Source
Katzung BG, ed.	Basic and Clinical Pharmacology. 15th ed.	McGraw-Hill; 2021
Brunton LL, Knollmann BC, eds.	Goodman & Gilman's The Pharmacological Basis of Therapeutics. 14th ed.	McGraw-Hill; 2023
Rush AJ, Trivedi MH, Wisniewski SR, et al.	Acute and longer-term outcomes in depressed outpatients requiring one or several treatment steps: a STAR*D report.	Am J Psychiatry. 2006;163(11):1905–1917
Trivedi MH, Fava M, Wisniewski SR, et al.	Medication augmentation after the failure of SSRIs for depression.	N Engl J Med. 2006;354(12):1243–1252
Nelson JC, Papakostas GI.	Atypical antipsychotic augmentation in major depressive disorder: a meta-analysis of placebo-controlled randomized trials.	Am J Psychiatry. 2009;166(9):980–991
Ruhe HG, van Rooijen G, Spijker J, et al.	Staging methods for treatment resistant depression: a systematic review.	J Affect Disord. 2012;137(1–3):35–45
UK ECT Review Group.	Efficacy and safety of electroconvulsive therapy in depressive disorders: a systematic review and meta-analysis.	Lancet. 2003;361(9360):799–808
Lefaucheur JP, Aleman A, Baeken C, et al.	Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation: an update (2014–2018).	Clin Neurophysiol. 2020;131(2):474–528
Geddes JR, Carney SM, Davies C, et al.	Relapse prevention with antidepressant drug treatment in depressive disorders: a systematic review.	Lancet. 2003;361(9358):653–661
Ghaemi SN, Boiman EE, Goodwin FK.	Diagnosing bipolar disorder and the effect of antidepressants: a naturalistic study.	J Clin Psychiatry. 2000;61(10):804–808
DeRubeis RJ, Siegle GJ, Hollon SD.	Cognitive therapy versus medication for depression: treatment outcomes and neural mechanisms.	Nat Rev Neurosci. 2008;9(10):788–796
American Psychiatric Association.	Practice Guideline for the Treatment of Patients with Major Depressive Disorder, 3rd ed.	American Psychiatric Publishing; 2010