The three flavors

Congress's blueprint for the standard drug benefit calls for participants to pay monthly premiums and to meet a $250 deductible. When the deductible is satisfied, the plan pays 75 percent of a person' s total drug expenses up to $2,250. So of the $2,000 in drug costs that remain after the deductible is paid, the plan pays $1,500 and you pay $500.

Enrollees who spend more enter the coverage gap, or so-called doughnut hole, paying all drug costs out of pocket until their total spending on prescription drugs for that year reaches $3,600, which is known as the "true out-of-pocket cost." At that point, when a total of $5,100 has been spent by both the enrollee and Medicare, the government pays up to 95 percent of any further expenses. (All amounts apply for 2006 and might change in future years.)

But Congress allowed insurers to stir benefits into other combinations that might prove attractive to seniors as long as the value of the benefits is at least as great as the standard plan's. The result is a confounding hodgepodge of offerings that fall roughly into three categories.

Standard plans. These follow the government blueprint exactly with a deductible of $250 and 25 percent coinsurance. None offers coverage in the doughnut hole. Premiums are generally low, but standard plans are not very common. In Philadelphia, for instance, no more than 5 of 51 PDPs are standard plans.

Equivalent or alternative plans. These may have no deductible or one lower than $250. Instead of paying a percentage of the expense, you make copayments of specified dollar amounts. An equivalent plan may work well for seniors who take few drugs or lots of inexpensive generics, because they would get coverage right away.

Seniors who join an equivalent plan are likely to find three or four drug tiers, with different copayments for each. Generic drugs, which usually make up the first tier, have very low copayments, usually under $10; the second tier includes preferred brand drugs, which require higher copayments, often ranging from $15 to $40. So-called nonpreferred brand drugs, which account for the third tier, come with still higher copayments to discourage their use when a cheaper, equally effective alternative is available. In this third tier, copayments can run up to $60 or $70 per prescription. Expensive specialty drugs such as Enbrel, an immune-system suppressant, make up the fourth tier. With almost all plans, seniors pay 25 percent of each drug in this tier.

Enhanced plans. These are the Cadillacs, offering coverage in the doughnut hole, a low (or no) deductible, and lower copayments in the drug tiers or both. Such plans may appeal to the 39 percent of beneficiaries whose total prescription expenses, including the government' s portion, fall between $2,250 and $5,100. A few insurers--Aetna, Cigna, and Pacificare--are offering doughnut-hole coverage for generic drugs, while Humana also covers brand-name drugs.

The fact that there are three basic plan types doesn' t mean that it's easy to figure out which is which. Sellers can use any name they think will appeal to consumers, and without standardized names or benefits, anything goes. Cigna and Humana call their enhanced plan Complete. WellCare' s Complete plan is its middle plan, more generous than its standard plan, which it markets under the name Signature, but less generous than its top-of-the-line Premier plan. You' ll have to check with the company to make sure that a plan offers coverage you want.