Prices for dozens of prescription painkillers have jumped by as much as 15 percent since Merck & Co. Inc. pulled its once-popular arthritis drug Vioxx from the market last year, researchers said on Thursday found.

Thirty-six pain medicines, including Mobic, Motrin and Relafen, saw price increases after studies linked Vioxx to heart problems and led to its withdrawal in September, according to the Consumers Union publication, “Consumer Reports Best Buy Drugs.”

The number of prescriptions for many of the non-steroidal anti-inflammatory drugs, or NSAIDs, also increased, the consumer group said.

Consumer Union’s findings come weeks after the U.S. Food and Drug Administration called on Pfizer Inc.‘s to pull its rival drug Bextra over similar heart problems and the added risk of a fatal skin condition. The agency also ordered stronger warnings on all pain medicines.

Vioxx, Bextra and Pfizer’s other pain drug Celebrex are a type of NSAID known as Cox-2 drugs that are thought to be easier on the stomach than older counterparts like naproxen or ibuprofen.

The report, which analyzed data from health care information firm NDCIHealth, also found 17 drugs dropped in price while 10 remained flat. It did not evaluate over-the-counter pain medicines.

Since Vioxx’s withdrawal, prices for prescription-strength Motrin, the ibuprofen marketed by Johnson & Johnson’s unit McNeil-PPC, rose 13.3 percent from $30 to $34.

Higher doses of privately-held Boehringer Ingelheim Pharmaceuticals’s Mobic, which is distributed in the United States by Abbott Laboratories Inc., jumped 10.6 percent while lower doses were up 6.7 percent.

Prescriptions for the highly-marketed drug also jumped in the wake of Vioxx’s demise, doubling from 314,000 to 742,000 since September, the report said.

Consumer Union’s Steven Findlay, who wrote the analysis, said Boehringer’s advertising showed the power of marketing and its impact on drug prices.

“Doctors and consumers are unquestionably swayed by the ads and promotions for costly new medicines, even when lower-cost options that are just as effective are available,” he said.

Boehringer officials have said Mobic was their second-best selling drug last year, up 44 percent.

Wyeth’s Lodinem cost $150 in September and now costs $170, or 13.3 percent, more. GlaxoSmithKline Plc’s Relafen also jumped 10.6 percent,

Costs for lower doses of Celebrex rose 1.5 percent, while higher doses rose 0.9 percent.

FDA officials have said data does not show if some patients benefit more from certain painkillers, and have called on companies for more studies

Still, Consumer’s Union said most studies shows NSAIDs “are equally effective,” adding that patients do not need more expensive prescriptions unless they do not respond to other, cheaper versions.

Instead, the group said consumers should stick to generic ibuprofen, naproxen and salsalate. While some of their prices also rose, they were still cheaper.

The cost of a 400 milligram version of generic ibuprofen rose from $24 to $26 since September as did generic salsalate, 3M Co. unit 3M Pharmaceutical’s brand name salsalate, called Disalicid, dropped 1.5 percent in price at $74.