Could this be a new wrinkle in the marketing plan? The drugmaker has received a subpoena from the US Attorney in Georgia, which is investigating the promotion of the popular wrinkle remover.

In a statement, Allergen says the subpoeana “broadly requests documents regarding promotional, educational and other activities” relating to off-label promotion of Botox for treating headaches. The drugmaker notes that Botox is currently in Phase III clinical studies that investigating the use of Botox for treating headaches, a usage not approved by the FDA. Allergen intends to cooperate with the investigation, but of course, notes that docs are free to prescribe the drug off label.

The news comes just one month after the FDA disclosed that Botox, Botox Cosmetic (type A) and Myobloc (type B) have been linked to various adverse reactions, including respiratory failure and death, following treatment for various conditions. Botox, which rang up $1.1 billion in sales last year, is approved to treat a variety of conditions including cervical dystonia, or rigid neck muscles. The adverse effects were found in both approved and unapproved usages.

The most severe adverse effects were found in children treated for spasticity in their limbs associated with cerebral palsy. Treatment of spasticity is not an FDA-approved use of botulism toxins in children or adults, the agency notes. There was no immediate breakdown available of the side effects, although Public Citizen, which filed a petition two months ago asking the FDA to issue stronger warnings, found 180 US cases of serious adverse events, including 16 deaths, four of which were in children.