More coinsurance makes beneficiaries' drug costs less predictable, said Caroline Pearson, a senior vice president at Avalere. It may also result in fewer affordable options if patients can't achieve any savings by substituting drugs in the same therapeutic class, she said. The shift toward coinsurance also means that Medicare beneficiaries will have to rely to a greater extent on cost-estimating tools like the Medicare plan finder to figure out how much they may owe out of pocket.