BETHESDA, Md. -- A U.S. advisory panel on Friday urged approval for an over-the-counter version of Prilosec, one of the world's best-selling prescription drugs, for preventing frequent bouts of heartburn.

The ruling moves prilosec, made famous by drug company Astrazeneca PLC as the "Purple Pill," a step closer to becoming the first drug in its class available without a doctor's order. Consumer products giant Procter & Gamble Co. owns rights to sell the over-the-counter drug and hopes to have it on the market early next year.

More than 40 million Americans experience frequent heartburn, defined as occurring at least two days a week, Procter & Gamble said.

The Food and Drug Administration Advisory Panel voted 16-2 to support nonprescription Prilosec for preventing recurring heartburn attacks. But the advisers urged a rewrite of proposed instructions to make sure patients understand how to take it properly and when to seek a doctor's advice.

Having Prilosec readily available on store shelves without requiring a doctor's order is "in the public interest," said Dr. Louis Cantilena, the panel's chairman. Many panelists "felt this would bring more symptomatic patients to the correct treatment," he said.

Prilosec recently was the world's best-selling drug, with annual sales topping $6 billion.

If approved, nonprescription Prilosec would cost about $1 per tablet, compared with the current cost of $4 per tablet for the prescription drug, Reuters quoted Procter & Gamble as saying.

The drug would compete with older nonprescription heartburn treatments, called histamine blockers, that offer quick relief shortly before or after a meal. Those drugs include pepcid, sold by Merck and Co. and Johnson & Johnson; Pfizer Inc.'s Zantac, and Glaxosmithkline PLC's Tagamet. Patients also can take antacids.

Procter & Gamble said most people with frequent heartburn are unsatisfied with current over-the-counter treatments.

Proposed packaging for Prilosec, a so-called proton pump inhibitor that curbs production of stomach acid, would direct patients to take one tablet a day, in the morning, for 14 days.

The company predicts annual U.S. sales of $200 million to $400 million for nonprescription Prilosec. Procter & Gamble will pay undisclosed royalties to Astrazeneca, which is working to maximize revenue before the prescription drug faces generic rivals. Procter & Gamble expects to have exclusive rights for the over-the-counter drug for three years.

Prescription Prilosec still would be available as a therapy for various heartburn- and ulcer-related conditions.

Astrazeneca is battling generic firms in court to keep cheaper, prescription copycats off the market as it tries to switch patients to a newer pill called Nexium.

The FDA, which usually follows its panels' advice, is expected to make a decision on the over-the-counter drug in the coming months. Panel members said proposed label instructions were confusing, and they urged major revisions before the drug is allowed over the counter.

One concern is that the packaging make clear that patients should consult a doctor if their heartburn persists because that may be a sign of a more serious condition.

They also wanted people to know that Prilosec is not intended to relieve acute heartburn attacks.