Viagra has been studied in four main studies including 1,690 men aged 19 to 87 years, where it was compared with placebo (a dummy treatment) for between 12 and 26 weeks.
Viagrat uuriti neljas põhiuuringus, milles osales 1690 meest vanuses 19– 87 eluaastat ning kus Viagrat võrreldi 12– 26 nädala kestel platseeboga (näiv ravim).