Salix Pharmaceuticals (Nasdaq: SLXP) must wait a little longer for a regulatory decision on its constipation treatment Relistor.

An approval decision was expected on April 27. But the U.S. Food and Drug Administration has notified the Raleigh-based company that it needs more time. The new target date to issue an approval decision is July 27. This extension does not call for any additional drug studies.

Relistor, an injectable drug, is already approved to treat constipation in patients taking opioid medications. The drug is used in patients with advanced illness who are receiving palliative care and do not respond to other laxative therapies. Salix last year filed a supplemental new drug application seeking to add treatment of constipation in patients taking opioids for noncancer pain as an approved use of the drug.
Opioids relieve pain by acting on receptors in the spinal cord and brain. But opioids’ mechanism of action also interacts with receptors in the gastrointestinal tract and causes constipation. Relistor can reduce the constipating effects of opioids without affecting their pain-killing abilities.

Salix licensed Relistor from Progenics Pharmaceuticals last year in a deal that paid Progenics $60 million up front. Progenics could gain up to an additional $90 million in development milestones and $200 million in sales-based milestones. Salix has global rights to Relistor except with the exception of Japan, where Ono Pharmaceuticals holds rights to the drug.