There is not enough awareness about the link between loss of hearing and Viagra and similar erectile dysfunction drugs, according to new research.

The study was carried out by researchers from the Charing Cross and Royal Marsden Hospitals in London and Stoke Mandeville Hospital in Buckinghamshire has been published in The Laryngoscope journal. They say that hearing loss associated with Pfizer's Viagra (sildenafil) and other phosphodiesterase type 5 (PDE-5) inhibitors, Eli Lilly's Cialis (tadalafil) and Bayer's Levitra (vardenafil), has recently been reported, but few studies have evaluated the causal link.

Against this backdrop, 47 cases of sensorineural hearing loss with a temporal association with PDE-5 inhibitor ingestion were obtained from both published literature and pharmacovigilance agencies. Some 88% of reports were unilateral with an even left/right distribution and hearing loss occurred within 24 hours of ingestion of a PDE-5 inhibitor in 66.7% of cases. Viagra accounted for over 50% of cases.

In addition to the 47 cases, a further 240 reports of hearing loss occurring after PDE-5 inhibitor use were submitted from the US Food and Drug Administration’s adverse events reporting system and from clinical trials. However, these were not included in the final analysis since there were no accompanying case histories.

The researchers add that there is "increasing evidence that PDE-5 inhibitors may induce sensorineural hearing loss via plausible physiological mechanisms". They conclude that "there needs to be more awareness of this disabling side effect among healthcare professionals responsible for prescribing this drug".

The link between ED drugs and hearing loss is not a new one and in 2007, the FDA announced labelling changes for PDE-5s so that the possibility of problems was more prominently displayed.

Viagra useful in MS?

Meantime, researchers at the Autonomous University of Barcelona say they have discovered that Viagra "drastically reduces" multiple sclerosis symptoms in animal models with the disease.

The study, published in Acta Neuropathologica, demonstrates that a practically complete recovery occurs in 50% of the animals after eight days of treatment. Researchers are confident that clinical trials soon will be carried out in patients given that the drug is well tolerated and has been used to treat sexual dysfunction in some MS patients.