SNRIs after SSRI failure — dosing, dual action and safety (MEQ)

(i) Switch justification and STAR*D. She has a documented non-remission after an adequate adherent SSRI trial with confirmed unipolar course. Cross-class switch is appropriate. STAR*D Level 2 showed broadly similar remission after SSRI failure among bupropion-SR, sertraline and venlafaxine-XR — so venlafaxine-XR is reasonable, not uniquely mandatory; choose with her headache/tension phenotype, prior SSRI exposure, and preference after counselling.^[1][9]

(ii) Venlafaxine-XR plan and dual-action band. Example: start venlafaxine XR 75 mg orally each morning (or 37.5 mg for 3–7 days if activation-sensitive), then increase toward 150 mg and, if needed and tolerated, 225 mg daily, reviewing efficacy and BP. Mechanism teaching: lower doses are predominantly serotonergic; noradrenergic reuptake inhibition is recruited as dose rises (Blier healthy-volunteer dose map; Debonnel clinical physiological low-vs-high dose data) — so do not claim full dual action at the first 75 mg tablet.^[2][3] Cross-taper sertraline over 1–2 weeks depending on dose and symptoms, watching serotonergic overlap.^[9]

(iii) Monitoring. Baseline already includes BP, Na, LFTs — recheck BP after each substantial increase; early review (within 1–2 weeks) for nausea, activation, insomnia and suicidality; measurement-based mood scores at 2–4–6 weeks; sodium vigilance if older age or symptoms (class antidepressant hyponatraemia association); sexual function inquiry; never combine with MAOI.^[4][10][9]

(iv) Discontinuation counselling. Venlafaxine has a short half-life and is a classic agent for discontinuation syndrome (dizziness, electric-shock sensations, flu-like symptoms, irritability) after abrupt stop or missed doses. This is not addiction in the opioid sense. Plan: do not stop suddenly; taper when discontinuing; if severe symptoms occur, reinstate previous dose then taper more slowly — consensus panel recommendations support structured clinical management.^[5]

(v) Alternatives. If pain becomes dominant (e.g. neuropathic features), duloxetine (e.g. 30 mg then 60 mg once daily, up toward 120 mg if needed) has MDD RCT support at 60 mg and programme data for painful symptoms.^[6][7] Reboxetine is not a casual default: Eyding’s meta-analysis including unpublished data found overall ineffectiveness and potential harm with publication bias in the published literature.^[8]