Shares of K-V Pharmaceuticals (KV.A) continued to trade higher Friday morning a day after a doctors’ group clarified that the company’s Makena birth drug isn’t identical to lower-cost versions of the drug.

The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine said in a joint statement that physicians should understand the “inherent differences” between Makena, which has Food and Drug Administration approval, and drugs made using compounding processes.

“Healthcare providers understand that evidence-based medicine is the foundation of clinical practice,” K-V Pharmaceuticals said in a statement. “Access to FDA-approved Makena for clinically-indicated patients is an important public health priority.”

Evidence from a study that supported the use of one of Makena's compounds, known as 17P, was based on Makena rather than a drug obtained from compounding pharmacies, the groups said. Certain payer coverage policies had been influenced by a false belief that the unapproved lower-cost drugs are the same as Makena.

“These policies should be modified to ensure that clinically-indicated patients have unencumbered access to FDA-approved Makena, consistent with their healthcare provider's medical judgment,” the drug maker said.

Makena is a hormone medicine that reduces the risk of a pre-term delivery in women who have delivered prematurely in the mast.

Shares of pharmaceutical giants Pfizer (PFE) and Merck (MRK) traded higher on Friday amid a broader market rally. 

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