Can Flomax (tamsulosin) be used to help pass kidney stones?

Tamsulosin for Kidney Stones: Efficacy and Recommendations

Tamsulosin is effective for facilitating the passage of ureteral stones, particularly those larger than 5mm, and should be offered as medical expulsive therapy (MET) for uncomplicated ureteral stones ≤10mm, especially distal ureteral stones. 1

Mechanism and Efficacy

Tamsulosin works as an alpha-1A receptor antagonist that:

• Relaxes ureteral smooth muscle
• Inhibits ureteral spasms
• Dilates the ureteral lumen
• Facilitates stone passage

Evidence for Ureteral Stones

The evidence strongly supports tamsulosin use for ureteral stones:

• The American Urological Association (AUA) guidelines specifically recommend alpha blockers as medical expulsive therapy 1
• Meta-analyses show tamsulosin increases stone passage rates by approximately 29% compared to control treatments 1
• Tamsulosin is particularly effective for stones >5mm (RR 1.44,95% CI 1.22-1.68) but shows less benefit for stones ≤5mm (RR 1.08,95% CI 0.99-1.68) 2
• Beyond improving passage rates, tamsulosin also:
  • Reduces time to stone passage
  • Decreases pain and colic episodes
  • Reduces analgesic requirements 2, 3

Evidence for Renal Stones

For renal stones, the evidence is more mixed:

• Some studies show tamsulosin increases stone clearance after shock wave lithotripsy (SWL) of renal stones (73% vs 55% clearance rate) 4
• However, more recent research suggests limited benefit for renal stones after SWL, with a stone-free rate of 53.57% for tamsulosin vs 48.27% for control (p=0.680) 5

Clinical Recommendations

For Ureteral Stones

1. Stones <10mm with controlled symptoms:

   • Observation with periodic evaluation or MET with tamsulosin is appropriate 6
   • Tamsulosin 0.4mg daily for up to 28 days is the standard dosing 7, 2

2. Stones >10mm:

   • Surgical treatment is typically required
   • Both shock wave lithotripsy (SWL) and ureteroscopy (URS) are acceptable first-line treatments 6

For Renal Stones

1. Stones ≤20mm in non-lower pole:

   • SWL or URS are first-line options 1
   • Tamsulosin may be considered as adjunctive therapy after SWL, though evidence is mixed 4, 5

2. Stones >20mm:

   • Percutaneous nephrolithotomy (PCNL) should be offered as first-line therapy 1
   • SWL should not be offered as first-line therapy 1

3. Lower pole stones ≤10mm:

   • SWL or URS are recommended 1

4. Lower pole stones >10mm:

   • SWL should not be offered as first-line therapy 1
   • URS or PCNL are preferred 1, 6

Important Considerations

• Patient selection: Tamsulosin is most effective for ureteral stones >5mm 2
• Duration: Treatment typically continues for 28 days or until stone passage 7
• Side effects: Common side effects include dizziness, headache, and ejaculatory dysfunction (reported in about 13.4% of male patients) 4
• Contraindications: Use caution in patients on other alpha blockers or medications for erectile dysfunction
• Patient counseling: Inform patients about the "off-label" use of tamsulosin for kidney stones 6

Special Circumstances

• Infection with obstruction: In patients with obstructing stones and suspected infection, urgent drainage of the collecting system with a stent or nephrostomy tube is mandatory before addressing the stone 1
• Patients on anticoagulation: Consider ureteroscopy rather than SWL if anticoagulation cannot be discontinued 1

Tamsulosin represents a low-risk, potentially beneficial adjunct to standard care for facilitating stone passage, particularly for ureteral stones larger than 5mm.