FDA decided that entire class of PD-5 medications would bear an extra warning on their label about the possible risk of suffering sudden hearing loss when under treatment.

FDA especially refers to impotence drugs, such as Viagra, Cialis and Levitra and Revatio, a drug for pulmonary hypertension.

Viagra and Revatio is manufactured by Pfizer and Cialis by Eli Lilly. Levitra it was developed by GlaxoSmithKline and Bayer HealthCare and is jointly promoted by GSK and Schering-Plough Corporation in the United States.

According to FDA, all manufacturers have agreed to display on their products’ label ‘more prominently the potential risk of sudden hearing".

The FDA began its investigation of a possible link between sudden hearing loss and PD-5 drugs after the publication of an article in the last April about a man who experienced sudden hearing loss after taking Viagra.

FDA ear nose and throat specialist Dr. Robert Boucher discovered 29 reports of sudden hearing loss in case of Viagra intake. These reports date since 1996, when Viagra started to be marketed.

There are over 40 millions of prescriptions for the four drugs that will have the sudden hearing loss risk warning on their labels. The other three drugs contain a similar active substance with Viagra.

FDA spokeswoman Rita Chappelle, told CNN that the 29 cases of sudden hearing loss are a number relatively small, ‘but because we're talking about a person's ability to hear, we thought it was important to make the label clear that this is a possible event".

Viagra had already a mention on its label of a hearing loss possibility, because a few cases were reported during testing phase. But, usually hearing loss appears also within other conditions like advanced age, diabetes, heart disease, smoking. Some of these also lead to impotence, so when in Viagra treatment and these conditions are also present, it isn’t clear that only Viagra triggers sudden hearing loss.

Boucher told CNN: "We don't know enough to say that it's ironclad caused by the drugs, but we see enough to say we can't ignore it either". He also added: "This is basically a public health announcement to let people decide if they want to take the drug".

FDA recommended that man that take the impotence treatment drugs and experience sudden hearing loss should immediately stop taking them. However, patients taking Revatio and experiencing hearing loss should not stop their treatment, because it could be life-threatening, but there are advised to contact their doctor immediately.