WASHINGTON (AP) _ The Federal Trade Commission on Thursday ordered the makers of Doan's back pain pills to run ads stating that there is no evidence the product is more effective than other pain relievers.

The commission's decision marked yet another step in its nearly 3-year-long battle against Novartis Consumer Health, makers of Doan's. The FTC filed its initial complaint in 1996, alleging that the advertising for Doan's was deceptive and made unsubstantiated claims that the product was better than other over-the-counter back pain relievers.

The company ceased such advertising in May of 1996, but the commission ruled that such misbeliefs about the product continue to exist.

Under Thursday's order, packaging and advertising for Doan's would be required to carry the following message for one year: ``Although Doan's is an effective pain reliever, there is no evidence that Doan's is more effective than other pain relievers for back pain.''

Novartis is seriously considering appealing the decision to a federal court, company spokeswoman Kate King said. She said the company strongly disagrees with the FTC's findings that Doan's advertising ever claimed the pill is better than other products.

``Never did we say something about Doan's being superior,'' said King. ``This disagreement is really based on consumer perception of those claims.''

She said the company only claimed that Doan's is effective and that it contains an active ingredient that other analgesics do not have. Neither of these claims have been challenged, King said.

The FTC has long held that Doan's implied superiority with such slogans as: ``If nothing seems to help, try Doan's. It relieves back pain no matter where it hurts. Doan's has an ingredient these pain relievers don't have.''

In its opinion, the commission concluded in a 4-0 decision that even though the ads no longer run, they have created a false belief that still lingers among consumers. The commission also noted that the company spent $65 million, mostly in 15 second television and radio ads, to promote this message.

One of the commissioners, Orson Swindle, dissented in part with the decision to impose corrective advertising. He said he did not feel there was adequate proof that false beliefs about the superiority of Doan's continues to exist.

Last year, an administrative law judge upheld the FTC's 1996 ruling that Doan's ads were unsubstantiated, after the company had appealed. But the judge refused to order the company to run corrective ads.

Under Thursday's order, Doan's would have to carry the corrective statement for one year on packaging and advertising, except radio and television ads of 15 seconds or less, and until the company has spent as much on Doan's advertising as it did annually during the eight-year campaign.