New research shows a sharp rise in the number of Connecticut doctors who are prescribing drugs to injured people on workers' compensation at higher prices than if the drugs were bought at pharmacies.

The study conducted by Workers Compensation Research Institute, a research organization based in Cambridge, Mass., compared 23 states and found that doctors are increasingly dispensing drugs, often at substantially higher prices than at retail pharmacies.

The study found that prices paid for drugs dispensed by doctors rose rapidly while the price of medications sold at pharmacies have changed little or declined.

In Connecticut, the frequency and cost of drugs given to patients by doctors grew the second fastest among the states studied. The share of workers' compensation payments for prescription drugs dispensed by doctors in Connecticut jumped from 16 percent to 37 percent between 2008 and 2011.

The data for the study included almost 5.7 million prescriptions paid through workers' compensation for about 758,000 claims between 2007 and 2011.

"We rarely see a medical cost driver that has grown this rapidly," said Richard Victor, executive director of the institute, which receives funding from employers, insurers that sell workers compensation policies and other sources.

The study looks at physician-dispensed drugs before and after a 2007 change in California law that reduced the price of physician-dispensed drugs to more closely match prices at pharmacies. Before the law, doctors were paid 85 cents per pill of Vicodin, for example, compared with 43 cents paid at pharmacies. After the reforms, the doctors were paid 52 cents per pill and pharmacies charged 48 cents.