Medical marijuana users are on the hook for more than $500,000 in unpaid bills for government-certified weed, raising questions about the effectiveness of Health Canada's troubled dope program.

Newly disclosed statistics show that Health Canada has sent final notices β€”and sometimes dispatched a collection agency as well β€” to 462 registered users since government marijuana first became available in 2003.

"Most of the 462 individuals who have received a letter regarding their accounts in arrears have had their shipment ceased," department spokesman Paul Duchesne said in an e-mail.

The unpaid bills, totalling $554,255 as of Dec. 31, have tripled in value in the last two years and have resulted in some seriously ill citizens returning to the black market for their medication. The marijuana distribution service was specifically designed to give patients a legal alternative to street dope.

Officials have handed 29 overdue accounts to collection agencies who so far have been able to recoup just $2,000.

The statistics, acquired through the Access to Information Act and questions to Health Canada, suggest a deeply flawed program, as the number of users in arrears has soared to about two-thirds of all 739 patients licensed to buy government dope.

A series of adverse court rulings since 2000 forced Health Canada into the medical marijuana business. The program licenses certified users who've been prescribed cannabis by their doctors, and allows them to grow their own, have someone grow it for them, or buy directly from the department.

Health Canada has paid Prairie Plant Systems Inc. more than $10 million to cultivate a strain of pot in a mine shaft in Flin Flon, Man. Accredited patients can then buy the dope, with a THC content β€” the active ingredient β€” of 12.5 per cent, for $5 a gram.

The department has said it plans eventually to end its licensing of home-grown dope, forcing all medical users to buy their supplies directly from the government, perhaps through pharmacy distribution. Prairie Plant Systems now couriers the weed in 30-gram packets directly to users.

Spokesmen for the department did not respond to requests for comment and reaction.

Grace period now 30 days

Health Canada previously allowed a 90-day grace period for payment but has since reduced it to 30 days before considering an account in arrears. Other restrictive changes have been made to the program in the last two years, including efforts to persuade doctors to keep doses low.

Many seriously ill medical users are impoverished, unable to work, and survive on disability payments, provincial drug plans and charity. Medical marijuana has never been assigned official drug status by Health Canada and is therefore not covered by pharmacare programs.

Users typically smoke marijuana to combat nausea and pain associated with chronic ailments, resulting from such infections as HIV and hepatitis C, after standard medicines fail.

Mark Schollenberg, 42, of Stoney Creek, Ont., uses marijuana to control chronic pain from a series of workplace injuries. Unable to work and on disability, he initially used street marijuana but changed his mind.

"I thought instead of causing myself any problems, I should get a licence and do it legally," he said in an interview.

With a doctor's approval, Schollenberg got a licence and ordered his first batch of Health Canada dope last summer, assuming Ottawa would cover the costs.

He was cut off in October, now owes $3,962.34 including interest, and is back on the street to purchase his medicine.

"I can't even afford the black market," he says of his five-gram-a-day requirement.

Jason Wilcox of Victoria currently owes Health Canada $6,770.06, a number that will increase with interest charges each month.

Wilcox, 37, has been HIV-positive since at least 1993, and needs 10 grams of marijuana daily for nausea, for severe pain in his foot and to help him sleep.

He says he became angry on learning that Health Canada charges users 1,500 per cent more than it pays Prairie Plant Systems for the dope.

"At that point, I refused to pay," he said in an interview. "Also, not to mention that their product is crap."

Wilcox and his wife Theresa Anne Genovy, who herself owes Health Canada $3,297.21 for medical marijuana, now grow what they can but must still return to the streets for their full doses.

"I have no other source than the illegal underground," he says. "The only medication I pay for in this province is cannabis."