Even though drugstores are often convenient to shop at, they can also cost you a lot of money if you're not careful.

Here's a rundown of some products that are marked up in a big way by drugstores.

Antacid tabletsAntacid Tablets
Markup: 399%

Those little chewable Tums and Rolaids that you pop so casually between meals can really add up. A 60-count package of these calcium-containing tummy tamers retails for $10.53 at the stores that Cashier Live surveyed, but costs just $2.11 at wholesale, according to Greenhaw. The tablets are technically vitamins and are listed generically as oyster shell calcium with vitamin D. And though generic versions are available, you're still going to pay a premium for the convenience of fast relief.

Pain Relievers
Markup: 398%

Stores can make more profit from selling Bayer and other brand-name aspirins, along with other commonly-used items on this list, because they're in high demand and shoppers are willing to pay more for them, Greenhaw says. According to his data, a 50-count bottle of Bayer that retails at $3.89, actually only costs stores 78 cents wholesale.

Other pain relievers also have high markups at drugstores, although not as much as aspirin, according to Greenhaw's analysis. A 24-count bottle of acetaminophen, which is commonly sold as Tylenol, has a 378% markup -- from 87 cents wholesale to $4.16 retail.

Naproxen, a pain reliever commonly used to relieve arthritis, is sold as the brand name Aleve. A 250-count bottle has a 364% markup -- from a wholesale cost of $2.99 to a retail price of $13.87.

VitaminsVitamins
Markup: 395%

Eating enough oranges (vitamin C) or beans (vitamin B-1) may be cheaper than buying vitamins. A 100-count bottle of vitamin B-1 has a 395% markup, with a $5 retail bottle costing a store $1.01 wholesale. A 100-count bottle of vitamin C has a 382% markup -- from $2.92 wholesale to $14.10 retail.

Nasal Decongestant PE
Markup: 392%

At $4.23 for a 24-count package of Sudafed, the cost of phenylephrine to relieve a stuffy nose, sinus and ears is almost five times the drugstore's cost of 86 cents wholesale.

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