Q. After I fell into the Part D doughnut hole, one of my drugs actually cost me less than I'd paid earlier in the year, when it was fully covered by my drug plan. How is this possible?

A. It sounds difficult to believe! But yes, it is possible and is now actually happening in some cases — if certain circumstances come together in a particular way.

See also: Medicare plans in 2012.

Remember that until the end of 2010 people who fell into the dreaded doughnut hole — the coverage gap in the middle of the Part D prescription drug benefit — had to pay 100 percent of the cost of their drugs until they'd spent a certain amount out of pocket in any one year.

But since the beginning of 2011, the pharmaceutical manufacturers have provided a 50 percent discount on brand-name drugs in the doughnut hole, as required by the new health care law, the Patient Protection and Affordable Care Act. So now, Part D enrollees pay half as much for those drugs in the gap as they did before.

And sometimes the 50 percent they pay is lower than the regular copay that their Part D plan charges for a particular drug in the coverage period that precedes the gap.

Here are some real examples:

Example 1: A Part D drug plan pays $108.58 to the manufacturer for a month's supply of the antidepression drug Lexapro 10 mg. The plan places this drug in its pricing level for "non-preferred brands," which requires a copay of $95 a month in the initial coverage period. But in the doughnut hole, this drops to $55.04 for a month's supply (50 percent of the drug's full price plus a small dispensing fee).

Example 2: A different Part D drug plan pays $63.68 to the manufacturer for a month's supply of the menopause drug Premarin 0.9 mg. The plan places this drug in its "preferred brand" pricing level and charges a copay of $43 a month in the initial coverage period. But this drops to $32.59 a month in the doughnut hole (50 percent of the drug's full price plus a small dispensing fee).

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