How well do men with spinal cord injuries respond to Phosphodiesterase type 5 (PDE5) inhibitors?

PDE5 Inhibitors in Men with Spinal Cord Injury

PDE5 inhibitors are effective and well-tolerated for treating erectile dysfunction in men with spinal cord injury, with success rates of 72-85% depending on the specific medication. 1

Efficacy of PDE5 Inhibitors in SCI Patients

• PDE5 inhibitors are effective in men with spinal cord injury (SCI), with clinical trials showing rigidity sufficient for penetration in 85% of patients using sildenafil, 74% using vardenafil, and 72% using tadalafil 1
• Tadalafil appears to have the highest efficacy ranking (81% SUCRA value) in network meta-analysis, followed by vardenafil (68%) and sildenafil (49%) 2
• Men with upper motor neuron lesions respond significantly better to PDE5 inhibitors compared to those with lower motor neuron lesions or cauda equina injuries 1, 3

Dosing Considerations

• PDE5 inhibitors should be used with caution and at lower initial doses in men with SCI due to potential delayed metabolism 4
• Dose titration is often necessary - more than 70% of patients on vardenafil and tadalafil required higher doses (20mg), while 55% of sildenafil patients responded to 50mg 1
• The mean duration of erection with these medications in SCI patients is approximately 34 minutes for sildenafil, 28 minutes for vardenafil, and 26 minutes for tadalafil 1
• Two-thirds of patients using tadalafil reported effects lasting longer than 24 hours 1

Safety Profile

• Adverse effects in SCI patients are generally mild and tend to diminish with continued use 1, 5
• The most common side effects include dyspepsia, headache, flushing, back pain, nasal congestion, myalgia, visual disturbance, and dizziness 4
• Discontinuation rates due to side effects are low - across studies, only 15 patients (including 7 using sildenafil) discontinued therapy due to adverse effects 5

Important Clinical Considerations

• Proper patient education is essential as incorrect use (lack of sexual stimulation, medication taken with large meals) accounts for many treatment failures 4
• Multiple trials with the medication may be required to establish efficacy 4
• For men with SCI who also have testosterone deficiency, combining PDE5 inhibitors with testosterone therapy may be more effective than PDE5 inhibitors alone 4
• PDE5 inhibitors remain the first-line treatment option for ED in SCI patients, particularly those with higher-level injuries 6, 3
• For patients with lower SCI who don't respond adequately to PDE5 inhibitors, intracavernous injection of vasoactive drugs may be preferable 6, 3

Treatment Algorithm

1. Start with a PDE5 inhibitor at lower initial doses in SCI patients 4
2. Consider tadalafil as potentially the most effective option based on recent network meta-analysis 2
3. Titrate the dose upward if initial response is inadequate 1
4. Ensure proper patient education about medication use (need for sexual stimulation, timing relative to meals) 4
5. For patients with upper motor neuron lesions, expect better response rates 1
6. For patients with lower motor neuron lesions who respond poorly to PDE5 inhibitors, consider alternative treatments such as intracavernous injections 6, 3
7. Consider combination therapy with testosterone in patients who also have testosterone deficiency 4