With the holidays and their promise of post-feast heartburn on their way, Procter & Gamble (NYSE:PG) plans to make Prilosec available over-the-counter. However, the fanfare is dampened by a false-advertising lawsuit filed by a Johnson & Johnson (NYSE:JNJ) and Merck (NYSE:MRK) joint venture.

The brouhaha is over the widespread availability of what was in its prescription-only days "the little purple pill," distributed by AstraZeneca (NYSE:AZN) before it lost patent protection. AstraZeneca's purple pill is now prescription-only Nexium, though it still gets royalties from P&G's sales of Prilosec.

Proton pump inhibitors like Prilosec in effect stop acid production altogether, instead of just slowing it down. Prilosec is the first of the category to be available on store shelves, and therein lies the threat. Prilosec will now directly compete with such over-the-counter products ase J&J/Merck's Pepcid and Pfizer's (NYSE:PFE) Zantac.

The lawsuit contends that P&G is marketing over-the-counter Prilosec as a remedy that will work right away, but that it actually needs to be taken for 14 days and sometimes doesn't provide relief for one to four days.

P&G insists that it has made no false claims.

According to a Wall Street Journalarticle (subscription required), Pepcid currently has about 16% of the market for over-the-counter heartburn medications. And it's a big market. According to the American College of Gastroenterology, over 60 million in the U.S. suffer from heartburn at least once a month, with 15 million dealing with the discomfort daily.

There's a lot riding on this rollout. P&G expects from $200 million to $400 million in annual sales from Prilosec. In early September, the consumer giant raised its guidance, with one major driver being robust initial shipments of the drug. It said it expects earnings for the July through September quarter to grow by 19% to 21%, with hopes to surpass analyst projections of $1.23 per share.

Obviously, the legal entanglement could raise the price tag on this product launch. The Journal article mentions that the lawsuit seeks to have the ads pulled as well as monetary damages for any lost Pepcid sales.

Will any of this give consumers a sour taste when adding Prilosec to their grocery carts? That seems unlikely. With the drug's traditional popularity and insurance companies pushing for use of cheaper over-the-counter versions, P&G has a lot to gain.

You can reach Alyce Lomax at[email protected].