Kenneth Buss had taken Xarelto, a blood thinner, for more than a year when his mail-order pharmacy refused a request to refill his prescription several weeks ago.

Buss, 79 and prone to dangerous blood clots, immediately contacted his physician, who urged Buss’ Medicare drug plan to approve the medication.

The request was denied. But Buss didn’t let the matter drop. Without coverage, a 90-day supply of Xarelto costs about $1,300 at a local pharmacy — more than 10 times what Buss had been paying.

“That killed me,” said Buss, who remembers phoning his Medicare plan and saying, “Excuse me, are you saying my doctor is wrong and you know better?”