NEW ORLEANS — Prices for generic drugs to treat heart failure can vary so widely that uninsured patients may not be able to afford them, a new study suggests.

Researchers surveyed 175 pharmacies in the greater St. Louis area encompassing eastern Missouri and neighboring Illinois to assess how much they charged uninsured customers for the generic drugs digoxin, lisinopril and carvedilol, which are used to treat heart failure.

The study, presented Tuesday at the American Heart Association’s Scientific Sessions, found that the combined cash price for the three drugs for 30 days ranged from $20.19 to $256.77 for the low doses of the drugs, with a median price of $67.98. High doses ranged from $12 to $397.58, with a median price of $70.68. Similar variations were seen for 90-day supplies.

“The idea for the study originated with one of our patients, a 25-year-old man with heart failure, who called the office and said he could not afford to fill a prescription for digoxin,” said the study’s lead researcher Paul J. Hauptman, M.D., of Saint Louis University School of Medicine in Missouri. “When I found out that a month’s supply was going to cost him $100, I couldn’t believe it. Like me, I think a lot of doctors assume that if you’re writing a prescription for a generic drug that it will be affordable — and that’s not necessarily the case.”

The study did not find a link between price and type of pharmacy, or median income associated with the zip code in which the pharmacy is located. Surprisingly, two major pharmacy chains did not have consistent pricing across their own stores.

Hauptman said it is common for patients with heart failure to take five or six medicines to manage the condition, making it even more difficult for patients to get the lowest combined price of the drugs they need.

“It’s not reasonable to expect patients who are sick and of limited financial means to call or visit half a dozen pharmacies to get the best price,” he said. “What is more likely to happen is that patients visit a pharmacy and find out that the drug is too expensive, so they don’t fill the prescription and therefore do not garner benefit from guideline-directed medical therapy.”

Since a greater understanding of pricing practices at the retail pharmacy level is required, the researchers said their study should be replicated across other parts of the country and with different generic drugs to treat other medical conditions.

About 5.7 million Americans are living with heart failure.

The results may have significant policy implications given the potential impact on costs incurred by patients and adverse outcomes if generic medications are no longer affordable for patients who are uninsured or underinsured.