Rajfer Tadalafil Daily Efficacy Study: Key Findings Explained in Plain Language
Daily tadalafil 5mg produced significant improvement in erectile function starting as early as day 2, with efficacy increasing through week 4.
Study overview
Conducted by
Dr. J. Rajfer et al., UCLA
Patients
Men with mild to severe ED
Duration
12 weeks (randomized, double-blind, placebo-controlled)
Published in
The Journal of Sexual Medicine
Year
2007
Key findings
Efficacy onset as early as day 2
Men reported improved erectile function within 48 hours of starting daily tadalafil. This rapid onset is possible because tadalafil begins accumulating immediately and its 17.5-hour half-life creates overlap between daily doses.
Full steady-state reached by day 5
Blood levels of tadalafil reached consistent therapeutic levels within 5 days of daily dosing, after which the drug maintained continuous effect.
Efficacy continued to improve through week 4
While the initial effect was fast, clinical improvement (measured by IIEF scores) continued to increase over the first month as the body fully adapted to the steady-state blood levels.
Placebo-adjusted improvement was significant
The difference between tadalafil and placebo was statistically and clinically meaningful across all severity groups.
What this means for you
Daily tadalafil at 5mg fundamentally changes the ED treatment paradigm. Instead of timing a pill before sex, you maintain a constant therapeutic level. The fact that it works from day 2 means you don't have to wait weeks to know if it's effective. By day 5 you're at steady state, and by week 4 you're at maximum benefit.
Limitations
The study was 12 weeks. Longer-term data comes from extension studies showing durability out to 2 years. Patients with severe vascular disease or those on nitrates were excluded. The study was industry-sponsored (Eli Lilly). Results may vary based on ED severity and underlying cause.
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