NEW YORK (CNN/Money) - Prilosec, one of the world's best-selling drugs, will most likely be sold over the counter to treat heartburn by Procter & Gamble, as a U.S. Food and Drug Administration committee voted Friday to approve the medication on a non-prescription basis.

The panel voted in favor of the over-the-counter version of Prilosec by a 16-2 margin and the FDA usually follows its panels' advice. The FDA has six months to act on the recommendation.

Procter & Gamble is seeking to market a nonprescription version of AstraZeneca PLC's Prilosec, as it holds over-the-counter rights to the "purple pill." If regulators approve, Prilosec would be the first in a class of drugs called proton pump inhibitors to become available without a prescription.

Procter & Gamble predicts annual U.S. sales between $200 million and $400 million for nonprescription Prilosec. The company would pay undisclosed royalties to AstraZeneca, which is working to maximize revenue before the prescription drug faces generic rivals. AstraZeneca is fighting to keep prescription copycats off the market while it tries to switch patients to a newer pill called Nexium.

About 40 million Americans experience frequent heartburn, defined as occurring two days a week or more, and there is a need for better nonprescription treatment, said Procter & Gamble.

"Most people with frequent heartburn are not satisfied with the OTC medications they're taking,'' said Keith Triebwasser, Procter & Gamble's senior director for regulatory affairs.

Proposed directions for nonprescription Prilosec would urge people to take one tablet daily, in the morning, for 14 days to prevent frequent heartburn. It also warns patients to notify a doctor if heartburn persists for three months or more because that may indicate a more serious condition.

Procter & Gamble said studies showed most patients understood the label and used the drug properly.

A concern, however, is whether some patients might take the drug long term without consulting a doctor, and that might delay care for serious problems with the esophagus.

If cleared by the FDA, nonprescription Prilosec would compete with older heartburn remedies known as histamine blockers. They include: Pepcid, sold by Merck and Co. (MRK: down $2.22 to $49.98, Research, Estimates) and Johnson & Johnson (JNJ: down $2.04 to $53.00, Research, Estimates); Pfizer Inc.'s (PFE: down $2.05 to $34.03, Research, Estimates) Zantac; and GlaxoSmithKline PLC's (GSK: up $0.25 to $41.10, Research, Estimates) Tagamet.

AstraZeneca (AZN: up $0.64 to $40.35, Research, Estimates) could continue to sell prescription Prilosec for various conditions even if the FDA approves the over-the-counter drug. Generic makers also may be able to sell prescription versions if they win a legal fight over Prilosec patents.

Shares of Procter & Gamble (PG: Research, Estimates) remained flat Friday at $93.85.  

--Reuters contributed to this story