The purpose of this study is to determine the efficacy of oral L-Citrulline on endothelial function and vasodilation in patients with coronary artery disease(CAD) by evaluating the brachial artery diameter in the antecubital area by ultrasonography.

Before prescribing the drug or placebo, the patients were evaluated via the ultrasound machine equipped. The brachial artery diameter in the antecubital area was measured by the ultrasound and was recorded. Then blood pressure cuff was attached on the arm and dilated 50mmhg above the systolic pressure and for 5 minutes remained the same level to induce ischemia at distal tissues until the occurrence of compensatory vasodilatation. Then the brachial artery diameter (as an estimation of FMD) was measured and recorded. After 4 minutes of administration of 2 puffs of nitroglycerin spray, the brachial artery diameter (as an estimation of NMD) was measured.

After 15 days treatment with the L-Citrulline or the placebo, the patients underwent the ultrasonography again and the above assessments were done.

Improvement of FMD to NMD ratio (before L-Citrulline prescription) to FMD to NMD ratio (after L-Citrulline prescription) is determined as "improvement of flow mediated dilation to nitroglycerin dependent vasodilation" evaluate.

Inclusion Criteria:

• history of documented CAD; flow mediated dilation to nitroglycerin dependent vasodilation (FMD/NMD)ratio less than 1

Exclusion Criteria:

• no documented CAD; flow mediated dilation to nitroglycerin dependent vasodilation (FMD/NMD)ratio equal /more than 1