Methionine-loading test: evaluation of adverse effects and safety in an epidemiological study

Background: Methionine loading test is commonly used to detect hyperhomocysteinemia in patients with arteriosclerosis and other conditions. As administration of methionine causes endothelial dysfunction in laboratory examinations, we explored whether loading with this compound leads to clinically relevant adverse effects, especially in vasculature. Methods and results: When studying genetic factors in arteriosclerosis we recorded acute complications during a standard methionine loading test (with a dose of 100 mg/kg bw) and assessed a 30-day mortality in a group of 296 patients with coronary artery or peripheral arterial disease and in 591 controls. Acute complications were observed in 33% of the women and 16.5% of the men. For each sex, the patients and controls exhibited the same proportion of complications. The most common symptom, dizziness, was attributable to methionine loading. In addition, isolated sleepiness, nausea, polyuria and decreased or increased blood pressure were observed in part of the subjects. None of the 887 individuals died within the 30-day period following the test. Conclusion: Our study suggests that although standard loading with L-methionine frequently causes transitory complications impairing perception and vigilance, the test does not have serious adverse effects on vasculature and may be considered a safe procedure.