drug,usual_doses,onset,half_life,useful_window
Sildenafil (Viagra),25 to 100 mg,30 to 60 min,2.6 to 3.7 h,Up to 12 h
Tadalafil (Cialis),5 to 20 mg on demand; 2.5 to 5 mg daily,"About 30 min, peak near 2 h",17.5 h,Up to 36 h
Vardenafil (Levitra),5 to 20 mg,About 30 min,3.9 h,Similar to sildenafil
Avanafil (Stendra),50 to 200 mg,15 to 30 min,6 to 17 h,Shorter than tadalafil