Sildenafil, tadalafil, and what “first-line ED therapy” actually means
PDE5 inhibitors are the right starting point for most men with erectile dysfunction. A urologist's practical primer on selection, dosing, and what to do when they fail.
When a patient presents with erectile dysfunction, the first-line treatment in nearly every guideline is a phosphodiesterase-5 (PDE5) inhibitor — sildenafil or tadalafil. They are safe, effective, and well-studied. They are also routinely prescribed badly.
Pick the right molecule
- Sildenafil: ~4 hour half-life. Dose 25–100 mg, ~1 hour before sex. Affected by fatty meals.
- Tadalafil: ~17.5 hour half-life. Either episodic (10–20 mg as-needed) or daily (2.5–5 mg). Less food-sensitive.
Daily low-dose tadalafil is underused. For men who want spontaneity, who experience situational ED, or who also have BPH symptoms, daily 5 mg is often the right choice.
When PDE5s fail
Roughly 30-40% of men don't get an adequate response. Before escalating to second-line therapy, confirm a few things: was the dose titrated to maximum? Was it taken on an empty stomach with sildenafil? Was there enough sexual stimulation? Are testosterone levels normal? Each of these is a common reason a PDE5 trial gets called a failure prematurely.
After honest first-line failure, the conversation moves to intracavernosal injections (alprostadil, Trimix), shockwave therapy, or vacuum devices — and sometimes back to a workup for vascular or psychogenic causes that were missed initially.
Tagged
- ED
- Urology
- Evidence