Questcor Pharmaceuticals Inc said it expects third-quarter sales of its gel Acthar for treatment of infantile spasms (IS) to be about 20 percent lower than the 161 new, shipped and paid prescriptions in the second quarter.

The company said its third-quarter sales to the IS market appear to be impacted by a combination of a lower national birth rate in 2008-2009 and the normal significant variability in prescription activity in the IS patient population.

During the second quarter, about 60 percent of its sales of Acthar was for treatment of IS, a rare form of childhood epilepsy.

The gel is not yet approved by U.S. health regulators for IS but based on guidelines published by the American Academy of Neurology and the Child Neurology Society, many child neurologists use Acthar to treat infants afflicted with this condition.

Acthar is currently approved in the U.S. to treat attacks of multiple sclerosis (MS). For the third quarter, the company said it expects modest sequential growth for MS-related Acthar sales.

Acthar has orphan drug status for IS, which would give the drug a seven-year exclusivity period if approved, and the company is pursuing approval from the U.S. Food and Drug Administration for the indication.

The company said it has completed the additional statistical analysis that the FDA had requested in May and intends to resubmit the marketing application for Acthar for treatment of IS in October.

Questcor also said it expects the rebate provision for the third quarter will be $2 million to $3 million higher than normal.

A portion of Acthar sales is for patients covered under Medicaid and other government-related programs and Questcor provides rebates related to products dispensed to Medicaid patients.

Shares of Questcor closed at $6.71 Friday on Nasdaq. (Reporting by Jennifer Robin Raj in Bangalore; Editing by Unnikrishnan Nair)