OKLAHOMA CITY — Following the sale of ApothecaryRx pharmacies to Walgreens, Graymark Healthcare said it is shifting its focus to sleep disorders, including obstructive sleep apnea.

Graymark is one of the largest providers of sleep medicine diagnosis and treatment, owning and operating diagnostic sleep centers that treat a wide range of sleep disorders, and also operates a medical equipment supply company that provides disposable and durable medical equipment.

"Millions of Americans suffer from obstructive sleep apnea, and many aren't aware they have a problem or that treatment is available in their communities," said Stanton Nelson, chairman and CEO of Graymark Healthcare. "As a pure-play sleep disorders company focused primarily on obstructive sleep apnea, we believe Graymark is better able to help people sleep better."

Graymark announced its sale of ApothecaryRx pharmacies, which operates 18 pharmacies across five states, to Walgreens in late August.