COLUMBIA, S.C. - South Carolina decided Wednesday to quit paying for Viagra for Medicaid participants who are sex offenders, but the state is unsure how many offenders may have been receiving the drug.

Robbie Kerr, the head of the state agency that oversees Medicaid, said he would like to end reimbursements for impotence drugs to all Medicaid recipients.

"I don't want to give Viagra to sex offenders, that's pretty ridiculous," said Kerr, director of the state Health and Human Services Department. "The point to me is not that we're paying for Viagra and sex offenders may somehow get it, the point is, 'Why am I covering Viagra at all?'"

Kerr said the Medicaid program could use the more than $100,000 it has spent on Viagra in the last 10 months to cover 70 additional children, pay for 10,000 vaccines or pay for nearly 3,000 blood pressure prescriptions.

However, Kerr said federal rules prevent him from eliminating payments for impotence drugs for all program participants. If the agency takes a rebate off any drug - whether it be Amoxicillan, Zyrtec or Allegra - then the department must cover all drugs "That's the federal rule. It's a stupid rule," he said.

Centers for Medicare and Medicaid Services spokesman Gary Karr said states have to cover "medically necessary treatments," but have the flexibility to decide what's medically necessary. Karr said South Carolina may be able to change its Medicaid plan.

Florida's Medicaid agency has adopted a new rule that denies Viagra and similar medications to everyone on Medicaid, unless they use the drugs to treat hypertension.

"What Florida has decided to do is say that, 'We don't believe that this is medically necessary. They have the right to do that," Karr said.

It's unclear how many sex offenders on Medicaid in South Carolina may have received Viagra, but the agency has begun reviewing whether more than 7,000 sex offenders in South Carolina have received reimbursements.

The agency receives about 20 to 25 percent rebates on prescription drugs, which amounts to about $150 million in savings. The Medicaid program fills more than 10 million prescriptions for some 600,000 people each year.

Kerr said the department has tried for years to not cover Viagra and other "lifestyle" drugs, and recently asked the federal government for a waiver for more flexibility in Medicaid.

"This is a taxpayer-funded program. We have limited resources," Kerr said. "And you have to question, is this the best use of our money?"

Kerr's decision Wednesday comes after the state agency received a letter from the federal government warning sanctions if continued to supply Viagra to sex offenders. More than 400 convicted sex offenders in New York and Florida were reimbursed for the drugs.

It's already difficult to get Viagra and other impotence drugs in South Carolina because they require prior authorization before being prescribed. The drugs aren't on the state's preferred list and a person must have a condition like multiple sclerosis, chemotherapy or coronary artery disease to receive them.

And, Medicaid recipients who are prescribed Viagra may receive only one prescription for three pills each month. The state is lowering the dose to one pill each month beginning in July.