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Australian scientists on Friday said they have cracked part of the mystery of why some drugs cause higher rates of potentially fatal abnormal heart rhythms, a step they claimed will make it easier to design safer drugs.
At least nine drugs have been taken off the market or severely restricted since 1996 because of dangerous effects on patients' heartbeats.
These drugs block one of the channels of the heart and can cause cardiac arrhythmia, which can lead to sudden cardiac death.
Experts from Sydney's Victor Chang Cardiac Research Institute said many drugs in development are also likely to be plagued by similar side-effects.
The institute said research from 2009 found sudden cardiac death affected about 0.1 percent of adults per year. Among patients with schizophrenia taking anti-psychotic drugs, the incidence is three times higher, at between 0.2 and 0.3 percent per year.
According to Professor Jamie Vandenberg, head of the Cardiac Electrophysiology Laboratory at the Victor Chang Institute, doctors have now found the mechanism which opens the gate to these channels.
"Just like a set of metal wires that carry electricity to light up our streets, our body has a series of channels that carry tiny charged particles called ions, into and out of cells, to trigger a heartbeat," he told ABC Science on Friday.
"Depending on the position of these gates, many common drugs attach themselves to these channels, blocking the ions from passing through.
"This causes what we call Long QT syndrome, where the length of the heart beat is longer than usual, which greatly increases the risk of arrhythmia."
Professor Vandenberg believes the "gate mechanism" will also apply to other channels important in the heart's electrical system, as well as those that control electrical communication in the brain.
He said that the biggest benefit of this research is that it should allow the better design of drugs so they no longer block these important electrical channels in the heart. It will allow patients the freedom and peace of mind to take their medication without the fear of their heart suddenly stopping.
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