A trip to the drugstore isn't a casual expense for many Americans these days. A just-released survey from Consumer Reports' subscribers shows only 33% of drug purchases were covered by insurance for the most part or in full. That's way down from the 65% coverage in 2002.

"Chain drugstores are still where the lion's share of drugs are purchased" said Consumer Reports' Tod Marks. "But more and more people are actually going online to purchase their drugs. About 10,000 supermarkets in the U.S. are equipped with drug stores. And more and more people are finding those extraordinarily convenient."

With so many choices, are there way to save on prescription drugs? Consumer Reports compared the cost of four common drugs at 13 different store and Web sites. It turns out prices for plavix, levoxyl, detrol, and alendronate varied significantly.

"We found that there was a tremendous price fluctuation for the same drug" said Marks. "You know sometimes of a hundred dollars or more for a single prescription."

Consumer Reports' price comparison for these four drugs shows Costco had the lowest prices overall. Web sites like AARP.com and Walgreens.com were also relatively inexpensive. But don't count out independent drugstores.

"They've received high scores for many many years from since we began our study from since we began our study of pharmacies, and we also found that many are competitive on price." said Marks

The bottom line: It pays to shop around for the cheapest prescription by checking out prices online, by phone, or in person.