A ban on direct-to-consumer advertising (DTCA) of new medicines during the first two years after regulatory approval could prove harmful to patients, the US Congressional Budget Office (CBO) has warned.

Pharmaceutical manufacturers spent $4.7 billion on DTCA in the US in 2008, or nearly a quarter of their expenditures on all promotional activities during the year, but concerns about the economic and health implications of this activity have led to recent calls - from the Institute of Medicine (IoM) and Members of Congress, among others - for two-year moratorium on DTCA for new products following approval from the Food and Drug Administration (FDA).

Such a ban would allow more time for safety concerns about a new drug to be revealed but it could also carry health risks, not least because some people who would benefit from a new drug might be unaware of its availability, says the CBO, which advises Congress on economic issues.

In a new paper considering the implications of limiting DTCA, Sheila Campbell of the CBO's microeconomic studies division examines why such a ban being proposed. One concern, she notes, is that DTCA may add to spending on drugs by consumers, insurers and government without providing enough benefits to justify the additional expenditures, or that it could encourage wider use of certain drugs than their health benefits would warrant.

Another concern is that DTCA for newly-approved medicines may lead people to use drugs whose potential risks were not fully discovered during the approval process. "The newest drugs on the market tend to be among the most heavily-promoted, raising the risk that more people will be adversely affected before steps can be taken to identify and address such potential safety problems," says Ms Campbell.

Moreover, researchers have found a link between the promotional activities that pharmaceutical manufacturers use to expand the market for their drugs and increased reporting to the FDA of adverse events from a greater number of people taking those drugs, she adds.

However, her report also suggests that delaying the widespread use of new drugs in this way could worsen rather than enhance public health, given that the positive effects of DTCA could be delayed. She points to studies which have found that such consumer advertising spurs people to seek treatment when they otherwise might not, and also that it improves patients' compliance with prescribed drug regimens. Therefore, for drugs whose health benefits outweigh their safety and other concerns, a moratorium might reduce their use by a section of the population who would benefit from them, she says.

Ms Campbell also suggests that, in some cases, a DTCA moratorium could postpone the realisation of a drug's true risks - if, for example, the number of people taking it was reduced sufficiently to prevent the product's full risks from being discovered as quickly.

Turning to the effects of a moratorium on drugmakers’ promotional activities, she suggests that it would probably lead them to increase their marketing and advertising to physicians, and this could mean a DTCA ban having little effect on the numbers of prescriptions filled for the product. Any change in the drug's price would depend on changes in demand - "to the extent that the effects on demand are likely to be limited, so too are the effects on prices," she adds.