Canadian Medicine

For three years now, the once-promising diabetes medication rosiglitazone (Avandia) has been waiting for the axe to fall. Sales plummeted after a linked the drug to a sharply increased risk of heart attack.

Since then, re have only confirmed that rosiglitazone increases heart attack risk in diabetic patients by 30 to 80%. Equally damning was data showing that this is not a class effect common to the thiazolidinediones - in fact rosiglitazone’s direct competitor pioglitazone has a fairly good cardiovascular risk profile.

Many diabetologists have suggested that rosiglitazone remains a useful option in reducing glycemia, so long as it’s used with care, and only in patients without heart problems. But pioglitazone’s better showing really kicks the last leg out from under this argument. Rosiglitazone delivers nothing that pioglitazone doesn’t, except for extra cardiovascular risk.

Rosiglitazone has had a , issued a few weeks after the FDA gave it one of their notorious “black box” warnings. Its indications for use were also tightened considerably. Since then, sales have fallen by about two-thirds. The end has been drawing near, and this time, Health Canada beat the FDA to the punch.

From now on, the drug will only be prescribed in Canada if patients sign a acknowledging that they’re aware of added dangers of heart attack, angina and heart failure, plus unspecified “other risks”. The patient must also certify their awareness that “there are other options to treat my diabetes.”

The physician, meanwhile, is enjoined not to use rosiglitazone-containing products except in cases when “all other oral antidiabetic agents, in monotherapy or in combination, do not result in adequate glycemic control or are inappropriate due to contraindications or intolerance.”

So farewell, then, Avandia. Neither patient nor physician is likely to go along with that, especially when there’s a boatload of promising new diabetes drugs hitting the market. Drugs whose hidden pitfalls, if any, have yet to be revealed.

What lesson may be gleaned from all of this? One reason rosiglitazone’s dangers went unnoticed for so long is that, while the drug brought much more cardiovascular risk than placebo, the effect was less noticeable when compared to other antihyperglycemic drugs like sulfonylureas and even the reliable standby metformin - because all of these drugs also increase the risk of lethal heart problems.

It may seem odd that, when cardiovascular disease is the thing most likely to kill diabetic patients, we routinely treat diabetes with drugs that increase the risk of cardiovascular disease. It seems even odder when we consider that there’s a safe, cost-free way to reduce blood sugar that actually improves cardiovascular health … that is, exercising and eating a healthy diet of low glycemic index foods.

Oddest of all, surely, is the fact that so many patients are apparently more comfortable with the idea of popping multiple pills with potentially grim side effects than they are with the idea of eating a few more vegetables and a bit less ice cream.
Owen Dyer

Expert witnesses fail to acquit BPA in the court of public opinion

Last month, Canada became the first - and still the only - country to formally declare bisphenol A (BPA) a toxin, listing the organic compound as hazardous both to human health and to the environment.

BPA is an endocrine disruptor that can mimic the effects of estrogen. In vivo studies have linked even very low concentrations with permanent changes to the brains and reproductive systems of laboratory animals.

Two years ago, Canada announced its intention to ban BPA from baby bottles, as did several US states. In the event, they were largely pre-empted by the industry, as the shower of negative publicity surrounding BPA made it commercially nonviable.

But BPA hardly went away. In fact, it’s ubiquitous. It may be found in cellphone casings, cash register receipts, and all sorts of packaging, including and especially canned food. It’s an extremely common ingredient in the epoxy linings that cover the metal on the can’s inside.

This, most experts agree, is the number one source of human exposure. In Canada, the age group with the highest detected levels of BPA is teenagers, followed by younger kids. These are also the age groups most likely to eat canned foods.

This month, a panel of international experts sat down in Ottawa to get to the bottom of the issue of BPA in food. The meeting was sponsored by the World Health Organization, with support from the FDA, Health Canada and the European Food Safety Authority.

Their conclusion? That canned food is indeed the main avenue by which we absorb BPA … and it’s not a problem. Their modeling shows that BPA coming in through food consumption matches the quantity going out through urine. BPA does not significantly accumulate in the body, says WHO, and therefore action to remove it from food packaging would be “premature”.

Why premature? Because, as WHO acknowledges, there are still several studies suggesting adverse health effects even at very low levels, and finding worse overall health in people who work around BPA, for instance in canneries. Some of the best quality studies have still to report their findings, so the WHO wants to keep its options open.

But WHO also didn’t want to hurt industry by causing a public health scare before it knew the facts, so it held the meeting behind closed doors and made participants sign confidentiality agreements.

This approach may have backfired. Several manufacturers, apparently unable to stand the strain of not knowing, pre-empted the conference’s findings by announcing plans to remove BPA from their products while the experts were still deliberating. Among these was the world’s largest, Nestlé.

But Nestlé only said it would remove BPA from its US products - though many such products will undoubtedly find their way onto Canadian shelves. Different solutions might apply in different parts of the world, said the company, depending partly on local “cultural sensitivities” and consumer preferences. In other words, where the public shows no sign of caring about potential toxicity, manufacturers are unlikely to worry about it either.