IRISH AND British scientists have found a way to warn if a patient will react badly to a medicine used in the treatment of epilepsy.
In rare cases the drug can cause severe breakdown of the skin and even death.
The research involved teams at the Royal College of Surgeons in Ireland and the University of Liverpool. They studied the genes of patients who reacted badly to the drug and identified a single gene that is a “biomarker” for those likely to experience drug side-effects.
“It is a test that identifies people who are at high risk of having a nasty reaction to a particular drug used in the treatment of epilepsy,” said Dr Gianpiero Cavalleri who headed the Irish group and jointly led the research with Liverpool.
“Carbamazepine is one of the most commonly used epilepsy drugs worldwide,” he said.
Even so, about one in 20 patients will react negatively to the drug. Some will develop a rash that will stop if the drug is withdrawn.
A much smaller number will develop “hypersensitivity syndrome” with blistering of the skin and potentially serious damage to the liver, Dr Cavalleri said.
Some will also develop Steven-Johnson syndrome, an even more severe reaction where the skin breaks down with the outer skin layers separating from the deeper layers. “It is a rare but very nasty reaction that can cause death,” he said, and withdrawal of the drug does not automatically reverse the condition.
The Irish group began looking at the genomes of patients receiving the drug in what is known as a “genome association”.
“You compare the genomes in people who have had the rash and those who have had a normal response,” Dr Cavalleri said.
Details of the research teams’ work are published this morning in the New England Journal of Medicine. They started searching for genome differences “and when we ran the study we found a peak”, he said. They then looked at Steven-Johnson syndrome patients and these also had what looked like a promising marker.
The Irish group then met the Liverpool researchers at a meeting and compared notes, realising they were getting similar results.
Liverpool was studying patients with hypersensitivity and the two centres began collaborating in full genome association studies, and pinpointed the specific gene associated with the negative drug reaction.
A person receiving the drug was 25 times more likely to be affected by carbamazepine than those who did not have the gene, Dr Cavalleri said.