George Forth, an 82-year-old diabetic who lives on about $1,400 a month, stumbled into a Medicare netherworld known as the doughnut hole.

Because his insulin and other prescription drugs cost more than $2,400 so far this year, the London-born Ventura resident has to pay additional costs without help from insurance, until catastrophic insurance kicks in thousands of dollars later. So far, that means $319 depleted from a toothpick budget made up of Social Security and a $200 monthly pension.

Similarly bleak math propelled 150 seniors and people with disabilities into a crowded Ventura workshop recently, where they waded through 56 Medicare drug benefit plans, almost all of them stamped by rising premiums and co-pays. They searched for the choice that covers the most drugs at the best price. Some waited two hours to sit with a counselor.

"This is very, very important," said Forth, craning his neck because he forgot his hearing aids. "It's the most prime thing I do."

Seniors have until Dec. 31 to enroll in or change their Medicare Part D plan for next year. Started two years ago to help seniors survive the cost of prescriptions, Part D allows people to sign up with private insurance companies that contract with the government to provide drug coverage.

"Everyone's coming in, and they don't have a clue over what to do," said Ventura County Medicare counselor Katharine Raley outside the Part D workshop. "The whole room filled up in five minutes."

Rising costs, changes in how virtually every stand-alone plan covers drugs, and current plans that won't be offered next year make choices confusing. Counselors worry seniors may have missed a letter telling them their current coverage is ending. They say that people who choose not to explore their options and instead stick with their current plan could pay more money for less coverage.

Californians who remain in the same drug plans can expect to pay about 31 percent more in premiums next year, from an average of $20.22 to $26.53 a month, according to a study from the California Healthcare Foundation. The most popular choice in California, a United Healthcare plan called AARP Medicare Rx Saver, is more than doubling its premiums ,from $9.80 to about $21.

The roller coaster ride

But as the price of plans that offer only drug coverage goes up, premiums for the private managed care plans that cover all of a person's Medicare needs are falling in California and across the nation.

The roller coaster ride makes Raley worry that if people shop for a plan based only on premiums, they may be covered for fewer drugs or face other barriers.

She said people need to consider whether a plan limits a particular drug quantity, meaning people who take more daily doses could pay exponentially more. Some plans mandate prior authorizations, meaning a doctor has to get approval from the insurance company before a medication is covered. Others require a person try one drug before being covered for another.

The requirements can snowball. Raley tells of analyzing one of next year's drug plans for someone who takes several psychiatric medications. The cost-sharing barriers would have brought disaster.

"With premiums and co-pays and medications that are not covered, it was $15,000," she said of the total out-of-pocket costs.

The cost of insurance is rising because the price of drugs is rising, said Mohit Ghose, spokesman with the America's Health Insurance Plans association. Other observers say that as companies enter into the third year of the drug program, they're basing premiums and co-pays on the actual costs of the program rather than on projections.

It could be worse. When Part D was launched, it was estimated that premiums in 2008 would average about $41 instead of the national average of about $32.

Critics complain the program offers seniors too many choices and headaches. They worry profit plays too big a role, meaning insurance companies make it harder for seniors to get drugs that don't make money.

But Ghose said the wide range of choices means seniors can hunt for a plan tailored to their needs. Because the private companies that offer the drug insurance plans compete with each other, prices stay affordable for beneficiaries and for taxpayers who fund Medicare.

"I think it's paternalistic to assume that seniors can't make choices when for two years running they've made the choices that are working for them," Ghose said, referring to an October AARP survey showing about eight of 10 seniors think they made a good choice.

But there are fewer options for people living in or near poverty. Last year, 14 insurance companies offered plans with reduced premiums or none at all to people with incomes of less than about $15,300. Only nine companies will offer such plans next year.

Out-of-pocket costs rise

Sandra Blaylock won't say how much she makes a month but said it isn't much. She won't tell how much she has to pay for medication but said it's way too much.

The 63-year-old Ventura woman, who lives on disability insurance, has diabetes, heart problems and a nervous system disorder. She takes 16 drugs a day and learned recently her insurance plan's premiums and other out-of-pocket costs are going up.

"I can't afford it," she said. "I have to find an alternative."

The doughnut hole generates the most fear. In 2008, the hole will begin when yearly costs reach $2,510, compared to $2,400 this year. At that point, people will pay for everything. Catastrophic coverage will kick in when out-of-pocket costs reach $4,050 and total drug costs pass $5,726. Then insurance companies will pay 95 percent.

Raley worries changes in the way insurers cover brand-name drugs could mean prescription costs will accumulate faster and people will fall into the doughnut hole quicker, as soon as March or April. Those enrolled in comprehensive managed care Medicare plans may qualify for some benefits for generic drugs, but people who need brand-name drugs will likely be on their own.

Jay Shoemaker and his wife are both perched on the edge of the doughnut hole this year and could fall in next year.

"I'm going to have to pay it," said the 82-year-old Ventura man. "I like living. I'm a diabetic. I have to have insulin three times a day."

Insurance companies don't like the doughnut hole any more than seniors because it poses an administrative nightmare, said Chris Ohman of the California Association of Health Plans. But the coverage gap is the only way the government can afford the costs of Part D so that seniors can get prescription drugs.

"The key is it's better to have the Part D and the coverage than it is not to," he said. "There are literally tens of millions of seniors who now have coverage for their drugs. It's hard to argue against that."