Sildenafil, Tadalafil and Vardenafil.

FDA informed healthcare professionals of reports of sudden decreases or loss of hearing following the use of PDE5 inhibitors Viagra (Sildenafil), Levitra (Vardenafil), Cialis (Tadalafil) for the treatment of erectile dysfunction, and Revatio (Sildenafil) for the treatment of pulmonary arterial hypertension.
In some cases, the sudden hearing loss was accompanied by tinnitus and dizziness. Medical follow-up on these reports was often limited which makes it difficult to determine if the loss of hearing was related to the use of one of the drugs, an underlying medical condition or other risk factors for hearing loss, a combination of these factors or other factors.
The PRECAUTIONS and ADVERSE REACTIONS sections of the approved product labeling for Viagra, Levitra, and Cialis were revised. FDA is working with the manufacturer to revise the labeling for Revatio.

Source: http://www.fda.gov/medwatch/safety/2007/safety07.htm