The Supreme Court cast doubt Tuesday on efforts by states to limit drug manufacturers' use of information about the prescription drugs that doctors like to prescribe.

The court took up a dispute between the state of Vermont and companies that sell doctors' prescribing information to pharmaceutical companies, though without patient names. The drug makers use the data to tailor their pitch to individual doctors.

The Vermont law had prevented the sale of information about individual doctors' prescribing records without the doctors' permission.

But several justices said the so-called data mining law raised troubling constitutional concerns because it appeared to make it harder for brand-name drug makers to state their case, while placing no similar restrictions on the state, insurance companies and others who favor the increased use of cheaper generic medicines.

Chief Justice John Roberts said the Vermont law seemed to be "censoring" what doctors could hear. Justice Ruth Bader Ginsburg said the court has ruled in the past that governments "can't lower the decibel level of one speaker so others can be heard better."

A federal appeals struck down the Vermont law as a restriction on commercial free speech that violates the First Amendment, but another appeals court rejected the constitutional challenge and upheld similar laws in Maine and New Hampshire.