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?