Published: 18:39 EST, 16 February 2015 | Updated: 19:58 EST, 16 February 2015
A new pill designed to combat both hearing loss and tinnitus is now being tested on patients for the first time.
The first drug treatment for both conditions has been developed by scientists in the UK and acts on brain cells involved in the processing of sound.
Laboratory studies have shown that the drug has the potential to reduce symptoms of age-related hearing loss and tinnitus.
Age-related hearing loss occurs when hairs in the inner ear that normally pass on sound signals to the hearing nerve become damaged or die
Around 50 per cent of men and women aged over 60 suffer from age-related hearing loss and 10 per cent of the population suffers from tinnitus.
Age-related hearing loss occurs when hairs in the inner ear that normally pass on sound signals to the hearing nerve become damaged or die, so the nerve impulses relaying sound to the brain are reduced.
Increasingly scientists believe that this form of hearing loss may also be linked to problems with nerve cells in the brain, too.
There is no cure. Hearing aids or cochlear implants can help some sufferers, but having implants requires surgery and hearing aids can be uncomfortable, increase the risk of infections and, even then, interpreting speech remains a challenge for some.
Tinnitus is the perception of sound in one or both ears when there is no obvious source. The type of sound heard varies from buzzing to ringing or hissing and can vary in pitch.
Although many people cope well with the symptoms, for around 1 per cent of the population it has a significant impact on their quality of life.
Hearing aids or cochlear implants can help some sufferers, but having implants requires surgery
Scientists have developed several treatments, from drugs affecting the central nervous system to electrical treatments and behavioural therapies, but the success has been limited.
The new drug works on a protein called Kv3 that helps form pores on the surface of nerve cells in the area of the brain connected with hearing. These pores allow potassium to enter the cells - the potassium is needed to help signals, such as hearing signals, pass between the nerve cells.
Researchers say there is evidence that levels of Kv3 become damaged or decline with age. This may cause patients difficulty in understanding speech and may be linked to tinnitus, too. Studies at the Institute of Experimental Medicine in Prague show the drug, known as AUT00063, can improve hearing in older animals, while research at University College London and the University of Southern Illinois has found the drug can have a beneficial effect on tinnitus.
Now University College London Hospital and ten other hospitals in the UK are embarking on a clinical trial, recruiting around 150 patients, who will receive four daily pills, or a placebo, every day for four weeks. This trial is focusing on patients who have had tinnitus for between six and 18 months.
If successful, future trials are likely to include people with longer term tinnitus.
Meanwhile, 100 patients with age-related hearing loss are taking part in a trial at the University of South Florida and other centres in the U.S. where they will take three capsules of AUT00063 or a placebo for four weeks.
Andrew McCombe, consultant ear, nose and throat surgeon at Frimley Park Hospital, Surrey, said: 'I have a suspicion that they may get better results in tinnitus sufferers than in age-related hearing loss.'
Meanwhile, a drug has been shown to slow the growth of cells that can lead to hearing loss and tinnitus. U.S. researchers have shown that salicylates, a type of non-steroidal anti-inflammatory drug, prevent the development of usually benign tumours, known as vestibular schwannomas.
These grow on the hearing and balance nerves in the ears and can cause gradual hearing loss, tinnitus, facial nerve paralysis and dizziness.
Currently, patients who are experiencing hearing issues as a result of vestibular schwannomas can undergo surgery or radiotherapy, but both can cause complications.
Salicylates work by inhibiting the COX-2 enzyme, which is responsible for inflammation and pain and is also thought to encourage the growth of vestibular schwannomas. The scientists hope their findings will lead to a clinical trial.