Bristol-Myers Squibb Co. and Sanofi fought back against an $8 billion lawsuit filed by Hawaii over marketing of their blockbuster blood-thinning drug Plavix, arguing in a countersuit that the state is trampling on their free-speech rights by demanding unnecessary warning labels. Hawaii claims the companies misleadingly marketed Plavix and failed to properly warn consumers in the state about its risks. Bristol-Myers and Sanofi argue that should be put on hold while their constitutional claims are reviewed.

“Hawaii’s lawsuit to extract civil penalties from the companies is an effort to compel speech,” lawyers for Bristol-Myers and Sanofi said in the suit, filed Tuesday in federal court in Honolulu.

Hawaii Attorney General Clare Connors said in a statement that the drugmakers’ lawsuit was a “shameful litigation tactic” to avoid a state court trial scheduled for April 27.

Hawaii and New Mexico, which also has sued over the drug’s marketing, claim the drugmakers didn’t disclose that the blood thinner, which generated $6.6 billion in sales in 2011, isn’t effective for as many as 30% of users. Many of the people who found it ineffective are of Asian or Pacific-Island descent.

These users don’t properly metabolize the drug due to a genetic trait, the states allege. The drugmakers dispute that claim in their countersuit.