DURHAM, N.C. (AP) — North Carolina's largest health insurer is clamping down on coverage of opioid prescriptions.

Blue Cross and Blue Shield of North Carolina says starting Sunday it's no longer covering first-time prescription of short-acting opioids for more than a seven-day supply. Initial prescriptions for more than seven days of immediate-release opioids will be automatically rejected at the pharmacy.

Limiting initial opioid prescription lowers the risk of addiction and chances of unused drugs hitting the street.

Blue Cross says up to 4,000 opioid prescriptions filled each month were exceeding seven days. That's about one out of seven prescriptions of this kind, down from one out of five three months ago.

The Durham-based health insurer says also starting Sunday it will require prior authorization before policy-holders receive a first-time prescription for extended-release opioids.