Can trazodone (antidepressant medication) cause flank pain?

Trazodone and Flank Pain

Trazodone is not known to directly cause flank pain as a common side effect, though it may contribute to urological complications that could present with flank pain in rare cases. 1, 2

Trazodone's Known Side Effect Profile

Trazodone is a serotonin receptor antagonist and reuptake inhibitor (SARI) antidepressant that is commonly used for:

• Treatment of major depressive disorder (150-300 mg/day)
• Off-label treatment of insomnia (25-100 mg/day) 1, 2

The most common side effects of trazodone include:

• Drowsiness/sedation
• Dizziness
• Headache
• Dry mouth 2

Potential Mechanisms for Flank Pain

While flank pain is not directly listed as a common side effect of trazodone in guidelines, there are potential indirect mechanisms that could explain flank pain in some patients:

1. Urological Complications: Trazodone has been associated with priapism (prolonged, painful erection) due to its alpha-adrenergic blocking properties 1, 3. In severe cases, this could potentially cause referred pain to the flank region.

2. Renal Effects: Though not specifically documented in the provided guidelines, medications that affect serotonin pathways can sometimes influence renal function, which could potentially manifest as flank pain.

Evidence from Guidelines

The available guidelines do not specifically mention flank pain as a direct side effect of trazodone:

• The American Academy of Sleep Medicine position paper discusses trazodone's use for insomnia and nightmares, noting side effects such as daytime sedation, dizziness, dry mouth/sinuses, and priapism, but does not mention flank pain 1.

• The AUA guideline on erectile dysfunction mentions trazodone's mechanism related to alpha2-adrenergic receptor antagonism but does not list flank pain among side effects 1.

Research Evidence

One study examined trazodone for painful diabetic neuropathy at low doses (50-100 mg/day) and found it effective for neuropathic pain, with side effects including dizziness, headache, and insomnia, but did not report flank pain 4.

Clinical Approach to a Patient with Flank Pain on Trazodone

If a patient on trazodone presents with flank pain:

1. Rule out common causes of flank pain first:

   • Urolithiasis (kidney stones)
   • Pyelonephritis
   • Musculoskeletal causes
   • Renal infarction
   • Abdominal aortic aneurysm

2. Consider medication timing:

   • Assess whether the onset of flank pain correlates with trazodone initiation or dose changes

3. Evaluate for urological complications:

   • Particularly in male patients, assess for priapism or other urological issues that could refer pain to the flank region 3

Management Recommendations

If trazodone is suspected as a potential cause of flank pain:

1. Discontinue trazodone if the clinical situation allows
2. Monitor for resolution of symptoms after discontinuation
3. Consider alternative medications for the original indication (depression or insomnia)
4. Document the adverse effect if confirmed by resolution after discontinuation

Key Takeaway

While trazodone is not commonly associated with flank pain in medical guidelines, any medication can potentially cause idiosyncratic reactions in individual patients. The temporal relationship between starting trazodone and the onset of flank pain, as well as resolution upon discontinuation, would be the most important factors in determining causality.