HOUSTON — The state's most populous county has become the nation's latest governmental entity to sue prescription drug companies amid a national opioid-drug epidemic.

Harris County, where Houston is located, filed its lawsuit in state district court in Houston on Wednesday, seeking unspecified damages. It accuses 18 drug manufacturers and distributors, as well as four doctors and a pharmacist, of creating a market that encouraged the over-prescribing of opioids and of knowing that their use could lead to addiction and other health problems.

According to the lawsuit, of the more than 2,500 opioid-related deaths in Texas in 2015, 318 took place in Harris County.

More than two dozen states, cities and counties around the country have sued pharmaceutical companies. The companies have generally denied wrongdoing.