The warning comes after six patients died in an NIH-sponsored study testing whether L-arginine can improve heart function after a heart attack. The study was terminated earlier than planned because of these disproportionate deaths.
All six deaths were among the 78 heart attack patients who added L-arginine to their normal medical treatment regimen. There were no deaths among the 75 heart attack patients who did not receive L-arginine.
"L-arginine therapy should not be given to patients following a [heart attack]," warn Johns Hopkins researcher Steven P. Schulman, MD, and colleagues. "L-arginine therapy in older patients with [stiff arteries] may worsen clinical outcomes."
Schulman's team reports the findings in the Jan. 4 issue of The Journal of the American Medical Association.
Heart attacks are particularly deadly for elderly patients because a person's blood vessels stiffen with age. L-arginine is known to reduce blood vessel stiffness and to improve blood vessel function.
But there are also theoretical reasons that L-arginine can be dangerous after a heart attack. The researchers note that the supplement may worsen the effects of cardiac shock among other possibilities. Much more study is needed.
In the meantime, heart attack patients are strongly advised to avoid taking L-arginine supplements.
"We noted a possible increased risk of death in older patients after [heart attack] while taking L-arginine compared with those taking a placebo (fake pill), leading to the early termination of the study," Schulman and colleagues write. "These findings have broad public health implications given the increasing availability and use of L-arginine in patients with and without established [heart] diseases."