Tadalafil for Sexual Dysfunction After Anal Sphincter Surgery
Tadalafil will not address the underlying problem and should not be added to the pelvic-floor rehabilitation program in this specific clinical scenario.
Why Tadalafil Is Not Indicated Here
The patient's sexual dysfunction stems from loss of sensory feedback from the anal sphincter, not from erectile dysfunction (ED) or vascular insufficiency. Tadalafil is a PDE5 inhibitor that works by:
- Improving penile blood flow to achieve and maintain erections sufficient for vaginal penetration 1
- Enhancing erectile rigidity through vasodilation 2
- Treating ED of organic, psychogenic, or mixed etiologies 1
None of these mechanisms address sensory nerve damage or loss of proprioceptive feedback from sphincter injury. 1
The Core Problem: Sensory Loss, Not Erectile Dysfunction
Mechanism of Injury from Sphincterotomy
- Lateral internal sphincterotomy (LIS) divides the internal anal sphincter to reduce resting anal tone, which can decrease resting sphincter pressures from ~60 mmHg to ~32 mmHg 3
- Trans-sphincteric fistulotomy disrupts both internal and external sphincter fibers, creating structural and functional deficits 4
- The resulting sensory loss eliminates afferent feedback that contributes to sexual arousal, particularly in patients who derive arousal from anal/perineal sensation 2
Why PDE5 Inhibitors Cannot Help
Tadalafil has been studied extensively in post-surgical sexual dysfunction, specifically after bilateral nerve-sparing radical prostatectomy where:
- Erectile function improved significantly (IIEF-EF score increase of 5.3 points with tadalafil 20 mg vs. 1.1 with placebo) 1
- However, continence recovery showed no benefit (no significant difference between tadalafil groups and control for urinary continence) 5
This demonstrates that tadalafil does not restore sensory or motor function to damaged sphincter mechanisms—it only enhances erectile hemodynamics. 5
What Actually Works: Pelvic Floor Rehabilitation
The evidence-based approach for sphincter-related sensory and functional deficits includes:
- Pelvic floor physical therapy to retrain proprioceptive pathways and improve sphincter coordination 2
- Biofeedback training to enhance awareness of residual sphincter function 2
- Sacral nerve stimulation (SNS) in severe cases, which showed 89% therapeutic success at 5 years for fecal incontinence by modulating afferent and efferent pathways 2
None of these modalities are enhanced by concurrent PDE5 inhibitor therapy. 2
Critical Pitfall to Avoid
Do not prescribe tadalafil simply because the complaint involves sexual function. The 2025 EAU guidelines emphasize that PDE5 inhibitors are indicated for:
- Vasculogenic ED 2
- Psychogenic ED 2
- Post-prostatectomy ED where cavernous nerve injury impairs erectile hemodynamics 1
They are not indicated for sensory neuropathy or loss of arousal due to peripheral nerve damage. 2, 1
Alternative Considerations
If the patient has concurrent erectile dysfunction (inability to achieve/maintain erections independent of the sensory loss), then tadalafil may be appropriate:
- Start with tadalafil 10 mg on-demand, titrate to 20 mg if needed 2, 1
- Expect improvement in erectile rigidity and duration, but no restoration of anal sphincter sensation 1
However, the question specifies that the problem is reduced arousal due to loss of sensory feedback, not erectile failure—making tadalafil mechanistically irrelevant. 1
The Bottom Line
Focus rehabilitation efforts on pelvic floor therapy, biofeedback, and potentially sacral neuromodulation if conservative measures fail. 2 Tadalafil addresses a different physiologic pathway (penile hemodynamics) and will not restore the sensory input lost from sphincter surgery. 2, 1