Common drugs can cause abnormal heart beats

Monday, January 31, 2011

SYDNEY - Many common drugs, including some antibiotics, anti-histamines and anti-psychotics, can cause a potentially fatal abnormal heart rhythm, known as arrhythmia.

The group of drugs most commonly associated with this side-effects are anti-psychotic drugs, taken by patients with schizophrenia and other psychiatric disorders.

Patients taking these drugs are up to three times more likely to die of sudden cardiac death due to an abnormal heart rhythm, the journal Nature Structural and Molecular Biology reports.

“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,” said Jamie Vandenberg, who heads the Cardiac Electrophysiology Lab at the Victor Chang Institute in Sydney.

“Depending on the position of these gates, many common drugs bind or attach themselves to these channels, blocking the ions from passing through.

“This causes what we call Long QT syndrome, where the length of the heartbeat is longer than usual, which greatly increases the risk of arrhythmia.”

It is estimated that around 40 to 50 percent of all drugs in development will block one of the main ‘channels’ that carries electricity in the heart, according to a statement from Chang Institute.

Consequently, they can cause arrhythmias, which are known to cause most sudden cardiac deaths.

Since 1996, nine drugs have been withdrawn from the market or had their use severely

restricted due to this serious side effect.

Researchers from Chang Institute have discovered a key clue as to why this happens, by understanding how the ‘gates,’ which effectively ‘open’ and ‘close’ the channel, operate.

Sudden cardiac death is unexpected death that occurs within one hour from the start of symptoms when death is witnessed.

Drugs that have been withdrawn or had their use restricted since 1996: Terfenadine (antihistamine), astemizole (antihistamine), grepafloxicin (antibiotic) , terodiline (antispasmodic), droperidol (anti-psychotic), lidoflazine (anti-arrhythmic), sertindole (anti-psychotic), levomethadyl (anti-opioid), and cisapride (gastric).

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