**5. Methadone**

Methadone is an opioid drug for treating pain. In addition, it is used for therapy of people addicted to opioids.

In the year 2014, about 7 million US citizens were abusing prescription drugs (source: National Center for Health Statistics). One of these drugs is methadone. Six recent case reports exposed an unknown before side effect of methadone abuse–the hearing loss [51–55]. The patients described in reports were young (age range 20–37) and were admitted to the hospitals because of methadone overuse. In all reported cases, the patients were deaf upon awakening (one perceived tinnitus), and in four of six cases, hearing loss was only temporary condition. The remaining two patients were unfortunately left with severe sensorineural hearing loss for the remaining observation time (2 and 9 months).
