Scientists tackle fatal drug side-effects

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Scientists tackle fatal drug side-effects

Danny Rose, AAP Medical Writer, AAP January 28, 2011, 4:34 pm

Australian scientists have taken a major step towards addressing the risk of heart failure caused by some of the world's commonly used drugs.

The issue has emerged since the mid-1990s and it has seen nine separate drugs - including an antihistamine, an antibiotic and even a gastric drug - pulled from availability or wound back in their approved uses because of concerns over the same unintended side-effect.

Professor Vandenberg, from Sydney's Victor Chang Cardiac Research Institute, said the drugs were known to bind to a specific part of the signalling system which controls a person's heartbeat.

They could cause cardiac arrhythmias - abnormal electrical activity in the heart - which had the potential for lethal complications.

Anti-psychotic drugs were particularly prone, Prof Vandenberg said, though they remained on the market because there were few alternatives and the benefit for patients was deemed to outweigh the risk.

"We've been aware of this problem now for about 15 years," Prof Vandenberg told AAP on Friday.

"These drugs were actually developed to target something else ... it might be an anti-psychotic (drug) that will hit a dopamine receptor.

"It then has this off-target effect of blocking this hERG ion channel ... which most drugs will stick to it even if they were designed to bind to something else."

It is the hERG ion channel that carries and regulates the tiny pulses of electricity which ensure a healthy heartbeat.

Prof Vandenberg's research has described the operation of a key part of this channel - a complex "gate mechanism" - which allows these pulses through but was also implicated in the off-target problem.

Understanding the form and operation of this gate should help in the redesign of existing and the development of future drugs that would avoid, instead of blocking, the channel, he said.

Patients taking anti-psychotic medications were known to be up to three times more likely than the general population to die suddenly from heart problems, and this was linked to their medication.

"The biggest benefit of this research that it should allow the better design of drugs so they no longer block these important electrical channels in the heart," Prof Vandenberg said.

"This should allow patients the freedom and peace of mind to take their medication without the fear of their heart suddenly stopping."The research is published in the journal Nature Structural & Molecular Biology.

http://au.news./a/-/latest/8734418/scientists-tackle-fatal-drug-side-effects/