A bill that would allow pharmacies in California to share patient prescription information with third-party businesses working for drugmakers was approved in the state Senate 21-16 Thursday.

Under the legislation, pharmaceutical companies could send mailings directly to patients suffering from illnesses such as cancer, Parkinson’s and schizophrenia. The drug manufacturers would contract with a mailing firm, which in turn would pay fees to pharmacies.

The bill is intended to offer a way for pharmaceutical firms to encourage patients to take their medicine as prescribed and to refill prescriptions if called for by their doctors, said Rocky Rushing, spokesman for the measure’s author, Sen. Ron Calderon, D-Montebello (Los Angeles County).

"This bill will provide public benefits that will help people live healthier lives," he said.

But critics say the legislation violates patient privacy rights and opens the door for medical identity theft. "There is nothing more private than our personal medical records, but this bill would let drug companies peek in our medicine cabinet to boost their profit," said Jerry Flanagan of Consumer Watchdog. "Once private medical information is transferred electronically, it is vulnerable to theft, accidental leaks and misuse."

Calderon amended the bill after a 17-17 defeat on the Senate floor last week to allow patients to opt out from mailings when they pick up prescriptions.

"It stops at the pharmacist’s counter if the customer opts out," Rushing said. "No information is forwarded to the mailing house."

The bill, which now moves to the state Assembly, was supported by, among others, the Mental Health Association in California and the National Association of Cancer Patients.

The California Medical Association opposed it, along with some consumer organizations.