TORONTO -- The amount Canadians spend on filling prescriptions at pharmacy counters has taken a dip for the first time since the Second World War, but health economists predict big shifts in the pharmaceutical industry will soon reverse that decline.

A new edition of the Canadian Rx Atlas, compiled at the University of British Columbia, found Canadians spent almost $23 billion on prescription drugs through retail pharmacies in 2012-13, or $650 per person -- down one per cent from five years earlier.

"On a per capita basis, spending on prescription drugs at retail pharmacies in Canada has been flat for the last five years," said Steve Morgan, a health economist at UBC's school of population and public health, and the atlas's lead author.

"But the calm surface of drug spending in the last few years belies what are dramatic transformations within the (pharmaceutical) sector," Morgan said from Vancouver.

The atlas analyzes retail spending for more than 10,000 medications within 33 categories using data from the health-care market research company IMS Brogan.

That analysis shows that brand-name "blockbuster" medicines that came to market in the 1990s to treat such common conditions as high blood pressure, high cholesterol, heartburn and depression no longer command the major share of prescription dollars.

In 2007-08, those drugs accounted for $8.7 billion, or 40 per cent, of all spending at retail pharmacies.

This year, annual spending for those classes of medications fell to $6.7 billion -- a drop of $2 billion -- mainly because of the expiration of patents for brand-name drugs, which expanded the market for cheaper generic versions.

Now, drug dollars are increasingly going to specialty or "niche" medications, Morgan said.

Spending on drugs for such diseases as rheumatoid arthritis, HIV, cancer and multiple sclerosis doubled to $3 billion in 2012-13 from five years earlier.

The atlas shows that while the average cost of a prescription for high blood pressure pills is about $27, filling a single script for an anti-inflammatory drug to treat rheumatoid arthritis, for instance, can top $2,100.

"You can imagine that the per-year (cost) of treatment for some patients on these things is in the order of $20,000," said Morgan.

In fact, more than a third of drugs now being developed by pharmaceutical companies are niche drugs, which he said will come to market with hefty price tags.

"The pharmaceutical industry is moving towards a new revenue model -- we see tell-tale signs of things to come from this Rx atlas. Policy makers must act now to ensure fair pricing and equitable access before spending gets out of hand again."

The atlas also revealed major differences in prescription drug spending between males and females over the last five years. Per capita spending for antidepressants taken by women was double that of men. In the 40-64 age group, for instance, women forked over $550 million per year for antidepressants, compared to $270 million spent by men.

Annual spending on antidepressants rose to $1.4 billion in 2012-13 from $1.3 billion in 2007-08, but such factors as population growth and an aging demographic don't fully account for the rising costs.

"Studies in the U.S. have shown that many people prescribed antidepressants do not have a psychiatric diagnosis, and that this is why antidepressant use is so common," commented Barbara Mintzes, an assistant professor in UBC's department of pharmacology and therapeutics.

"The volume of use we're seeing across Canada suggests that the same thing may also be happening here."

Among children and adolescents up to age 18, the atlas found unusually high spending on certain drugs for boys, specifically those to treat attention deficit hyperactivity disorder (ADHD) and asthma.

Morgan said drugs to treat ADHD were prescribed to boys three times more often than to girls, suggesting that there may be over-prescribing, possibly the result of gender stereotyping.

Consumer spending on prescriptions also varied across the country, with B.C. having the lowest amount of $511 per capita (27 per cent below the $667 national average) and Quebec at $820 per person (30 per cent above the average).

"The differences are enormous," said Morgan, adding there are likely several factors responsible for the spending disparity.

Overall, British Columbia residents purchase lower volumes of some drugs that are widely prescribed across the country, such as antihypertensives and cholesterol-lowering medicines.

Quebecers use more medications overall and pay higher prices than residents of other provinces, possibly because doctors tend to prescribe more expensive brand-name drugs and fewer generics.

The atlas, produced by UBC's Centre for Health Services and Policy Research, is based on retail pharmacy figures and does not include spending on medications by hospitals, cancer agencies or other disease-specific treatment centres.