WEST PALM BEACH, Fla. — Florida has long been the nation’s center of the illegal sale of prescription drugs: Doctors here bought 89 percent of all the Oxycodone sold in the country last year. At its peak, so many out-of-staters flocked to Florida to buy drugs at more than 1,000 pain clinics that the state earned the nickname “Oxy Express.”

But with the help of tougher laws, officials have moved aggressively this year to shut down so-called pill mills and disrupt the pipeline that moves the drugs north. In the past year, more than 400 clinics were either shut down or closed their doors.

Prosecutors have indicted dozens of pill mill operators, and nearly 80 doctors have seen their licenses suspended for prescribing mass quantities of pills without clear medical need.

New laws are also cutting off distribution. As of July, Florida doctors are barred, with a few exceptions, from dispensing narcotics and addictive medicines in their offices or clinics. As a result, doctors’ purchases of Oxycodone, which reached 32.2 million doses in the first six months of 2010, fell by 97 percent in the same period this year. The ban was phased in beginning last October, with a limit on the number of pills a doctor could dispense.