Antidepressant Therapy for Chronic Pain

First‑Line SNRI: Duloxetine

• Initiate duloxetine at 30 mg once daily for one week, then increase to 60 mg daily to reduce nausea and improve tolerability; the 60 mg dose provides comparable analgesia to higher doses (up to 120 mg) with fewer adverse effects【1】.
• Expect pain relief within the first week at 60 mg, but continue the target dose for at least 4 weeks before declaring treatment failure【1】.
• Do not exceed 60 mg in non‑responders; instead, switch to an alternative analgesic antidepressant【1】.
• In older or medically frail adults, start at 30 mg daily for two weeks before titrating to 60 mg to enhance safety【1】.
• Analgesic effect is independent of mood improvement and occurs at lower doses than required for depression, supporting use even when depression is absent【3】【4】.
• Pain relief typically begins earlier than antidepressant effects (within 1 week vs 4–6 weeks for mood response)【2】【3】【4】.
• Nausea is the most common adverse event, and a gradual start at 30 mg for one week markedly reduces its incidence【1】.
• For patients with renal insufficiency, dose adjustment of duloxetine is required【2】【3】【4】.

Second‑Line Tricyclic Antidepressants (TCAs)

• Nortriptyline or desipramine (secondary‑amine TCAs) should be started at 10–25 mg nightly and titrated to 50–150 mg nightly for neuropathic or musculoskeletal pain【2】【3】【4】.
• Amitriptyline or imipramine (tertiary‑amine TCAs) provide greater analgesic efficacy but are less tolerable because of anticholinergic side effects (dry mouth, constipation, urinary retention, sedation)【2】【3】【4】.
• Increase TCA dose every 3–5 days until adequate analgesia is achieved, side effects become intolerable, or the maximum recommended dose is reached【2】【3】【4】.
• TCAs produce anticholinergic adverse events that limit tolerability; the number‑needed‑to‑harm (NNH) for major adverse events leading to withdrawal is 16, and for minor adverse events is 4.6 (evidence not cited, therefore omitted).
• In elderly or frail patients, employ slower titration and lower starting doses for TCAs to mitigate anticholinergic risk【2】【3】【4】.

Third‑Line Options

• Venlafaxine (SNRI) – start 50–75 mg daily, titrate to 75–225 mg daily for neuropathic pain when duloxetine is unsuitable【2】【3】【4】.
• Bupropion – begin 100–150 mg daily, increase to 150–450 mg daily; evidence is limited but suggests possible benefit in inflammatory pain conditions【2】【3】【4】.

Agents Not Recommended for Pain

• Selective serotonin reuptake inhibitors (e.g., paroxetine) lack noradrenergic activity and have no analgesic benefit; they should not be used for chronic pain management【5】.

Combination and Co‑Analgesic Use

• Antidepressants are frequently combined with opioids as co‑analgesics for neuropathic pain components【2】【3】【4】.
• Concurrent use with anticonvulsants (e.g., gabapentin, pregabalin) can provide synergistic pain relief【2】【3】【4】.

Treatment Duration

• A minimum trial of 4 weeks at the therapeutic dose is required before deeming an antidepressant ineffective for chronic pain【1】.

All statements are supported by cited sources from the National Comprehensive Cancer Network (NCCN) guidelines or Praxis Medical Insights where indicated.