WASHINGTON (AP) — Last year pharmaceutical companies spent more than $4 billion urging patients like you to "ask your doctor" about their drugs. But if you want a prescription that won't empty your wallet, while still keeping you well, you might start asking your doctor about drugs you don't see on TV.

As unemployment continues to rise, experts estimate that 50 million Americans are without health care coverage, forcing many to bear the full cost of their prescriptions.

Compounding the problem are steadily rising drug costs. The senior advocacy group AARP reports that prices for the most popular drugs rose 8.7 percent on average last year, more than twice the rate of inflation.

Fortunately there are cheaper alternatives to many of these pills.

For example, AstraZeneca's acid reflux drug Nexium — the "purple pill" — was the second best-selling drug in the U.S. last year, with a hefty price tag of about $215 per month. But a drug from the same family, that works the same way, is available over-the-counter for about $20 a month as Prilosec.

Here are some important points to consider when looking to cut your prescription bill.

Q: Why would a cheap drug work as well as a more expensive one?

A: Because in most cases, drugs that are cheap today were once expensive. Patents on new drugs protect the product for about 20 years, allowing companies to charge the highest price the market will bear. But after the patent expires, or is successfully challenged in court, generic drugmakers launch cheaper versions, immediately driving the price of the drug down.

Generic drugs already make up nearly 70 percent of prescriptions in the U.S., and that percentage is expected to rise. Over the next five years products worth $137 billion are expected to go generic, including bloodthinner Plavix and cholesterol medicine Lipitor.

Q: If older drugs are so great, how come I've never heard of them?

A: In many cases you probably have, but don't realize it. When branded drugs go generic they lose their proprietary name and go by their scientific name. Many patients are familiar with Merck's cholesterol-lowering pill Zocor, but they might not realize the drug is now available for a portion of its original cost as simvastatin.

Q: But doesn't the Food and Drug Administration make sure new drugs work better than older ones?

A: No. The FDA does not judge drugs based on how they stack up against older medications. Rather, the agency weighs each drug's benefits against its risks. If the drug appears more beneficial than harmful, the agency is obligated to approve it.

But experts point out that benefits are sometimes slim, especially if one drug is significantly more expensive than another.

"Just because a drug is approved doesn't mean it works very well," said Dr. Lisa Schwartz, a researcher at Dartmouth College. "You really need to know more to see whether it's worth the cost."

Q: But aren't newer medications safer than older ones?

A: In some cases, yes. But generally speaking, new medications are more likely to have unexpected side effects than their older peers. Choosing an older medication is especially smart when newer medications don't offer clear benefits, says Dr. Nortin Hadler, of the University of North Carolina at Chapel Hill.

"Why use a new drug if there are no clear cut advantages and you have no sense of its long-term toxicities?" asked Hadler, who has written extensively on the overprescribing of drugs.

Perhaps the classic example of a much-hyped drug that turned out to be unsafe is Merck's painkiller Vioxx, which was pulled from the market in 2004 because it doubled the risk of heart attack and stroke.

The drug's effect was similar to aspirin or Advil, but Merck promoted it as easier on the stomach and sales peaked at $2.5 billion with 20 million Americans taking the drug. Consumers Union analyst Steven Findlay says the incident underscores the limits of premarket drug testing, which usually involves just a few thousand patients.

"With Vioxx turning out to be essentially unsafe for a lot of people, there was the recognition that new drugs coming on the market had not been fully evaluated in a diverse population," said Findlay.

Q: Shouldn't I just let my doctor make these decisions?

A: Only a licensed health care professional can prescribe a drug, and you'll want to defer to their judgment. But it's important to understand that physicians may not be completely objective when choosing a prescription.

The pharmaceutical industry spends about 90 percent of its $20 billion annual marketing budget pitching drugs to doctors, according to one estimate in the Journal of the American Medical Association.

With greater access to medical information online, consumers are increasingly seeking out independent reviews. Perhaps no information is more in demand than unbiased comparisons of medications.

Earlier this year Consumer Reports — the publishing division of Consumers Union — published its first issue of Best Drugs for Less. The magazine analyzes dozens of academic and government studies to make recommendations on the most affordable and effective medications.

Head-to-head comparisons of drugs are rare because of the time and money needed to conduct long-term trials.

"The information is out there, but it's not as much as we need," said Findlay.

That could change under an initiative kicked off earlier this year. The federal government has set aside $1.1 billion to study various medical treatments and see which ones work best, in an effort to cut out costly, ineffective treatments.