Health Canada is getting tough with patients who use government-certified medical marijuana, demanding full payment in advance before shipping the weed.

The move, effective Nov. 30, is designed to halt the rising number of accounts in arrears -- and force more patients to pay off old debts that now total more than $1.2 million.

"This change to a purchase-in-advance system will streamline the order and payment process and will prevent further increases to the debt load of the department," says a recent Health Canada letter issued to users.

More than 4,600 people in Canada are licensed to use medical marijuana to treat a wide range of conditions, including chronic pain, that may not be resolved by standard prescription drugs.

Several court rulings forced a reluctant Health Canada to get into the marijuana business in 2003 so that bona fide patients would not have to rely on the black market for supplies.

Most authorized users grow their own pot or have someone else grow it for them, all under licence, but some 800 are currently buying their medical marijuana from Health Canada.

The government sells dried marijuana for $5 a gram -- about half the price of street marijuana -- or 30 seeds for $20, plus GST and provincial taxes.

The marijuana, which has received poor reviews from many users for being harsh and ineffective, has a THC content of about 12.5 per cent. THC is the main active ingredient of the cannabis plant.

Previously, users could order and pay later. But hundreds of patients -- who are often seriously ill, unable to work and on welfare or disability pensions -- could not keep up with their Health Canada bills and built up large debts.

Beginning Nov. 30, Health Canada will require a money order, certified cheque, Visa, Amex or MasterCard before medical marijuana is shipped, normally by courier.

And those customers with accounts currently in arrears must agree to a payment plan with Health Canada before receiving any more product. Interest accrues on overdue accounts at 3.5 per cent, and Health Canada has sent 31 stale accounts to collections agencies.

Almost 1,100 customers have fallen behind in payments so far, forcing Health Canada to carry some $1.2 million in accounts overdue for more than 30 days. About half of the accounts have been overdue for a year or more.

"This change (in policy) does not alter Health Canada's commitment to providing fair and equitable access to marijuana for medical purposes and . . . will have no impact on the current authorization process," spokeswoman Christelle Legault said in an email.

"Health Canada is committed to working with persons whose accounts are in arrears, and will work with them through the department's accounts receivable to establish a payment arrangement plan."

A few users have their bills picked up by taxpayers.

Last year, Veterans Affairs reversed previous policy and said it will now pay for medical marijuana for any veterans licensed by Health Canada. At least eight veterans have benefited from the new policy.

Most users, though, cannot recoup the cost of their cannabis from governments because medical marijuana has never been assigned official drug status under the Food and Drug Act and is therefore not covered by any provincial pharmacare programs. The costs, though, can be deducted as medical expenses when filing annual income-tax forms.

One Health Canada customer in Surrey, B.C., says he will never be able to pay his $4,200 accumulated bill -- and argues he should not have to.

"This is something that's already paid for by the taxpayer and I shouldn't be paying it again," Tim Davison said in an interview.

Davison, 41, was cut off from Health Canada's weed about 18 months ago, and now must go to the black market for some of his marijuana, which he uses to control pain and nausea.

"I could incur a smear in my credit report," he says about his worries over speaking out. "I could aggravate Health Canada (and) they could come at me harder."

Health Canada has hired Saskatoon-based Prairie Plant Systems to produce and ship the marijuana to authorized users. For years the company grew the dope in an abandoned underground mine at Flin Flon, Man., but left the facility in the summer for an undisclosed location.

Department officials have said they will eventually phase out all personal production, forcing patients to order all their dope from the government, perhaps through pharmacy distribution.