Tadalafil's Effect on Bladder Relaxation
Tadalafil can help relax the bladder through inhibition of phosphodiesterase type 5 (PDE5), which is found in the smooth muscle of the bladder, prostate, and their vascular supply. 1
Mechanism of Action
- Tadalafil inhibits PDE5, which enhances cyclic guanosine monophosphate (cGMP) accumulation, causing smooth muscle relaxation in the lower urinary tract, including the bladder 1
- PDE5 is highly expressed in the lower urinary tract and supporting vasculature, and its inhibition can decrease smooth muscle cell proliferation, relax smooth muscle in the bladder neck, and modulate bladder afferent nerve activity 2
- The mechanism works through the nitric oxide (NO)-cGMP pathway in both the bladder and prostate 3
Clinical Evidence for Bladder Effects
- Tadalafil has been shown to improve storage symptoms in patients with lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) 2
- In clinical studies, tadalafil 5 mg once daily significantly improved International Prostate Symptom Score (IPSS) storage subscores compared to placebo 2
- Laboratory studies demonstrate that tadalafil enhances cGMP accumulation and potentiates relaxation in prostate tissue 4
Dosing for Bladder/Urinary Symptoms
- The American Urological Association recommends 5 mg daily tadalafil as a treatment option for patients with LUTS/BPH, regardless of comorbid erectile dysfunction 5
- This is a moderate recommendation with Grade B evidence level 5
- The recommended dose for BPH treatment is consistently 5 mg once daily 6
Clinical Considerations
- Tadalafil resulted in a mean change of -5.4 points in IPSS compared to -3.6 points with placebo, with a difference of -1.74 points 5
- Tadalafil is particularly beneficial for patients who have both LUTS and erectile dysfunction 3
- Unlike alpha-blockers and 5-alpha reductase inhibitors which can cause sexual dysfunction, tadalafil improves sexual function while addressing urinary symptoms 3
Combination Therapy Considerations
- Clinicians should not offer the combination of low-dose daily 5 mg tadalafil with alpha blockers for LUTS/BPH as it offers no advantages in symptom improvement over either agent alone 5
- This combination is not recommended particularly given the higher side effect risk 5
- However, laboratory studies show that combining tadalafil with tamsulosin (an alpha-blocker) results in enhanced inhibition of neurogenic contractions of human prostate and bladder neck tissue in vitro 4
Safety Considerations
- The primary contraindication for tadalafil is concomitant use with nitrate medications, which can cause severe hypotension 7
- Most common adverse effects include headache, flushing, rhinitis, and dyspepsia 6
- Cardiovascular risk assessment should be performed before prescribing tadalafil 7
In conclusion, tadalafil 5 mg daily is an effective option for bladder relaxation in patients with lower urinary tract symptoms, with the added benefit of improving erectile function in those with comorbid erectile dysfunction.