Par Pharmaceutical last week asked a federal court to tell the FDA to back off and allow the company to detail docs about using its Megace ES to treat AIDS-related wasting.

The appetite-stimulating hormone, originally approved to treat breast cancer, is indicated for anorexia, cachexia and unexplained, significant weight loss in patients with AIDS. So what’s the problem? As Par’s complaint argues, FDA regs bar not only off-label promotion – encouraging unapproved uses for approved drugs – but also “purport to criminalize a manufacturer’s truthful and non-misleading speech about the FDA-approved uses of a prescription drug to physicians who may use the drug for approved uses but are more likely to use the drug for unapproved uses.”

At issue, the drug maker says, is “The government’s ‘misbranding’ theory,” which Par says sets up a Catch 22: when detailing docs about on-label uses of a drug in a medical facility where physicians prescribe off-label, companies are guilty of “misbranding” based on the agency’s “intended use” rule unless they change labeling to add information on the off-label uses – which would be illegal under the “new drug” rule. Getting a new indication approved typically takes years and can cost millions of dollars.

The resulting threat of prosecution for off-label promotion thus “chills Par’s speech,” says the complaint, and the company “seeks declaratory and injunctive relief to ensure its ability to engage in this protected speech free from the risk of criminal liability.”

The case could have ramifications far beyond the question of “intended use,” particularly in the wake of the Supreme Court’s decision in favor of commercial prescription data providers. The free speech defense for off-label marketing “has been a sleeper all along,” said John Kamp, executive director of the Coalition for Healthcare Communication. “Par’s going to blow it wide open.”

The suit is reminiscent of the First Amendment case filed by Allergan seeking protection of “truthful and non-misleading” marketing efforts for off-label uses of Botox. Allergan dropped that suit last year as part of its $600 million settlement of off-label marketing charges with the Justice Department. But advocates of easing off-label marketing regs were cheered by the Supreme Court’s 6-3 decision in Sorrell v IMS Health in June. The court concluded, in essence, that governments could not prohibit commercial speech because it was too effective.

Par’s case also brings to mind one that’s farther along in the second circuit court of appeals, US v. Alfred Caronia and Peter Gleason, a rep and a doctor convicted of off-label promotion. In that case, a group of 11 drug and device companies calling themselves the Medical Information Working Group filed a friend of the court brief calling the conviction “constitutionally indefensible” in light of the IMS decision.