Regulators are issuing fewer citations to drug companies for false and misleading advertisements and are taking longer to do it, a congressional report says.

With annual spending on direct-to-consumer drug advertisements at $4.2 billion and growing, the government has limited ability to curb distribution of ads that violate federal rules, according to the report being released Thursday.

From 2002 through 2005, it took the Food and Drug Administration four months on average to draft, approve and send warning letters and other correspondence to companies that were in violation of the rules, government auditors said.

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Between 1997 and 2001, before FDA lawyers began reviewing the letters as a matter of policy, it took just two weeks on average to issue the letters. The number of letters fell off by about half between the two time periods.

The Government Accountability Office also said the FDA lacks an effective way to screen, review and track the more than 10,000 ads and Web sites brought to the agency's attention each year. The amount has doubled in just four years.

The Health and Human Services Department, the FDA's parent agency, acknowledges that the FDA's six reviewers cannot scrutinize everything so they focus on those ads with the greatest potential to affect public health.

The department said the lengthy legal reviews give the FDA more teeth because the letters that are sent rest on a more solid legal foundation.

"As a result, companies take our letters more seriously and quickly react to the problems identified therein," the department said in written comments to the GAO, the investigative arm of Congress.

The report said companies do comply with the letters, albeit slowly sometimes, when asked to produce follow-on ads that set the record straight.

Fuller reviews of ads, according to the department, would require vast numbers of new employees.

In a draft of a letter to be sent Thursday to the White House, Sen. Herb Kohl, D-Wis., asks President Bush to give the FDA more money to review and regulate direct-to-consumer ads. Kohl, along with Republican Sens. Bill Frist of Tennessee and Charles Grassley of Iowa, requested the report.

"If we are serious about protecting the health of consumers in our country, then we need an FDA capable of reviewing DTC (direct-to-consumer) ads and taking swift action when necessary. This report tells us that were nowhere close to that goal," said Kohl, who will become chairman of the Senate panel with jurisdiction over the FDA budget.

Spending on direct-to-consumer advertising of prescription drugs grew at almost 20 percent each year between 1997 and 2005, far outstripping the 9 percent growth in spending on research and development, according to the report. In 2005, drug companies still spent far more on R&D — $31 billion — and on ads and other promotions that targeted doctors — $7 billion — than they did on consumer ads.

Drug companies claim consumer ads help educate patients about diseases and conditions, leading to earlier diagnoses that can save the health care system money.

Critics say the spending promotes inappropriate drug use, especially when alternative drugs may be more suitable, and thereby drives up costs. The painkiller Vioxx, for example, was heavily advertised before its removal from the market over health concerns. A recent Institute of Medicine report recommended a two-year ban on advertising newly approved drugs.

The report also found federal efforts to rein in false and misleading ads often fall flat. When the FDA did send out letters in 2004 and 2005, it did so eight months on average after the flagged ads first appeared. At that point, more than half the ads were no longer even in print or on the air, the GAO found.

Television and magazine advertising accounted for about 94 percent of direct-to-consumer drug ad spending in 2005, according to the report. The most heavily advertised drugs are to treat chronic conditions, including asthma and high cholesterol.

The United States and New Zealand are the only countries that allow direct-to-consumer advertising of prescription drugs.