YONKERS, N.Y. -- For consumers who pay for all or most of their prescription drugs out of pocket, a new price study by Consumer Reports finds that it pays to shop around. Not only do prices vary from store to store for the same drug, but the fluctuations can be dramatic -- sometimes more than $100 for the same prescription -- even with the same chain, depending on whether consumers are filling their prescriptions in, say, Omaha, Nebraska, or Billings, Montana.

Consumer Reports placed more than 500 calls to 163 pharmacies nationwide to gauge price differences among four prescription drugs, three name brand medicines and one generic. For a three-month supply of pills for the urinary incontinence drug Detrol, for example, the price ranged from $365 to $551. CR also found significant price disparities for the two other name-brand drugs it studied: for Plavix (which prevents blood clots), the spread was $382-$541, and for Levoxyl (for treating hypothyroidism), prices ran from $29 to $85. And for the generic alendronate (for osteoporosis), the price range was $124 to $306.

In CR's small scale market-basket study, Costco was the cheapest for the four drugs CR sought quotes for, followed by AARP.com and Wal-Mart. Walgreens and Rite-Aid were among the priciest for the four drugs.

Besides calling different stores and comparison shopping, other cost-saving tips include:
-- Don't rule out independents: Though they're not the cheapest overall, many mom-and-pop pharmacies are highly competitive and offer top notch service.

-- Talk to your employer: Benefits administrators can provide details about pharmacy benefit managers, also known as PBMs.

-- Buy generics: They can cost 20 to 50 percent less than their brand name equivalents.

-- See if there's a discount program: Some stores have programs for those 50 and older; other programs are open to anyone without insurance.