Pfizer developed the drug to treat angina, and considered shelving it when it performed poorly in human testing. But when Pfizer tried to reclaim leftover pills from study participants, it discovered that many didn't want to return them.
美商輝瑞藥廠研發此藥原本是為了治療心絞痛，因在人體試驗時發現效果不佳，原擬放棄回收，但是許多參與試驗的受試者卻拒絕交出藥丸，探究原因才發現此藥的另一「副作用」──促進勃起功能，藥廠轉而發展壯陽藥。