In a patient on bupropion (Wellbutrin) who is experiencing itching and has been started on sertraline, what medication can be used to treat his anhedonia and chronic pruritus?

Mirtazapine is the optimal medication for addressing both anhedonia and chronic pruritus in this patient

Mirtazapine should be added to or replace the current regimen, as it uniquely addresses both the anhedonia (through noradrenergic and specific serotonergic activity) and chronic pruritus (through antihistaminic properties and documented antipruritic efficacy).

Clinical Reasoning

The Dual Problem

Your patient presents with two distinct but interconnected issues:

1. Anhedonia - a core depressive symptom inadequately treated by the current bupropion + sertraline combination
2. Chronic pruritus - potentially drug-induced (bupropion can cause hypersensitivity reactions including pruritus 1, 2) or idiopathic

Why Mirtazapine is the Answer

For Anhedonia:

• Mirtazapine has documented efficacy in treating anhedonia through its unique mechanism: α2-adrenergic antagonism increases norepinephrine and serotonin release, while 5-HT2 and 5-HT3 receptor antagonism provides specific serotonergic effects 3
• Unlike SSRIs alone, which can sometimes worsen anhedonia, mirtazapine's noradrenergic activity specifically targets motivational deficits

For Chronic Pruritus:

• Mirtazapine is explicitly recommended for generalized pruritus of unknown origin (GPUO) in the British Association of Dermatologists guidelines 4
• It is listed as an alternative antipruritic agent for drug-induced pruritus 4
• Multiple systematic reviews confirm mirtazapine's antipruritic efficacy across various pruritus etiologies 5, 6
• Its potent H1 antihistamine activity provides additional antipruritic benefit

Practical Implementation

Dosing Strategy

• Start: 15 mg at bedtime (leverages sedating effects, which diminish with higher doses)
• Target: 30-45 mg/day for optimal antidepressant and antipruritic effects
• The sedation at lower doses can be beneficial if insomnia is present

Managing the Current Regimen

Critical Decision Point: Evaluate if bupropion is causing the pruritus:

• Bupropion can cause delayed-onset hypersensitivity reactions including pruritus and urticaria 1, 2
• If pruritus began or worsened after bupropion initiation, discontinue bupropion before adding mirtazapine
• If pruritus predates bupropion or timing is unclear, you can add mirtazapine while monitoring

Regarding Sertraline:

• Sertraline has documented antipruritic properties, particularly for hepatic pruritus 4 and chronic pruritus generally 5, 6, 7
• Continue sertraline as it may be contributing to itch control and provides additional antidepressant coverage
• The combination of mirtazapine + sertraline is commonly used and generally well-tolerated

Alternative Considerations (If Mirtazapine Fails or Is Contraindicated)

For Pruritus Specifically:

• Paroxetine or fluvoxamine: Strong evidence for antipruritic effects 8, 7, with 68% response rate in chronic pruritus
• Gabapentin: Recommended for GPUO 4 and has documented efficacy 9
• Naltrexone: Particularly effective for opioid-induced or refractory pruritus 4, 9

For Anhedonia Specifically:

• Cariprazine (adjunctive): Recent evidence shows significant benefit for moderate-to-severe anhedonia in MDD 10, though this is a more specialized option requiring psychiatry consultation

Common Pitfalls to Avoid

1. Don't assume antihistamines alone will work: Traditional H1 antihistamines have limited efficacy in chronic pruritus without urticaria 4

2. Don't overlook bupropion as the culprit: Hypersensitivity reactions can occur weeks after initiation 2. If pruritus is drug-induced, continuing the offending agent while treating symptoms is futile

3. Don't use gabapentin if hepatic pruritus is suspected: Guidelines explicitly recommend against it in this context 4

4. Monitor for serotonin syndrome: Adding mirtazapine to sertraline increases serotonergic load, though the risk is low. Watch for agitation, confusion, tremor, or autonomic instability 11

5. Warn about weight gain and sedation: Mirtazapine's most common side effects; sedation typically improves after 1-2 weeks

Monitoring Plan

• Week 1-2: Assess tolerability (sedation, appetite changes)
• Week 2-4: Evaluate pruritus improvement (should see response if effective)
• Week 4-6: Assess anhedonia and overall depressive symptoms
• If no improvement in pruritus by week 4, consider alternative etiologies and refer to dermatology for comprehensive evaluation 4