LANSING - Pharmacies may soon be required to display what they charge for the most popular prescriptions after an investigation found significant price differences from store to store.    

Surveyors for the state attorney general called more than 200 pharmacies around the state and requested prices for 10 commonly prescribed drugs.

The survey revealed that in many communities, the pharmacy with the highest price for a drug often charged about four times more than the pharmacy with the lowest for the same prescription. In Saginaw, for example, the survey found that the price for a month's supply of Nasonex allergy inhalers ranged from $12.99 to $106.25.

If passed, the bill would require that pharmacists post at their counters a list of their prices for the 150 top prescriptions and their generic alternatives. Pharmacists are currently required to provide this information to customers who ask for it either in person or over the phone.

Nate Bailey, communications liaison for Attorney Gen. Mike Cox, said 17 pharmacies are being investigated for price gouging as a result of the survey.

In addition, pharmacies that refused to give price information over the phone have been asked for a written explanation, he said.

Bailey said separate legislation to create an online listing of prescription drug prices similar to systems in Maryland and Florida has already passed the House.

The online information would have to be updated monthly, he said.

"Everyone talks about the problems with prescription medication, but this is a simple thing we can do right now," he said.

Andrea Rybicki, communications director for the Michigan Pharmacists Association, urged customers to purchase all their prescriptions at a single pharmacy with the best overall price, even if it would be cheaper to use two or more.

Having a complete list of prescriptions allows a pharmacist to spot harmful drug interactions, she said.

"A prescription isn't a product so much as a service, so you can't compare it to, say, a pair of blue jeans," Rybicki said. "We want to encourage people to look at more than price."

Pharmacies have little to do with setting prices for prescriptions, which are largely determined by the price the manufacturer charges them, plus an additional service charge, she said.

Bill Knox, associate state director of government affairs for AARP, said the legislation "would be crucial to helping older Michiganians shop for the lowest priced generic alternatives."

The AARP Web site, www.aarp.org, has information about national price averages for drugs, but customers need localized information to effectively comparison shop, he said.

Sponsors of the legislation include Reps. Roger Kahn, R-Saginaw Township; Stephen Adamini, D-Marquette; Gary McDowell, D-Rudyard; and Steve Bieda, D-Warren.

The bill has been referred to the Committee on Health Policy.