Abstract
A 19-year-old-man was admitted to our hospital with intermittent chest pain. The day before admission, he had been diagnosed with enteritis and prescribed clarithromycin. He had experienced severe chest pain three times after taking clarithromycin; thus, acute coronary syndrome (ACS) was suspected. Emergent coronary angiography showed normal coronary arteries; however, the result of a subsequent acetylcholine provocation test was positive. We diagnosed him to have ACS caused by coronary vasospasms and suspected clarithromycin-induced Kounis syndrome. Although more common in older patients, Kounis syndrome must be suspected and a thorough medication history should be taken whenever a patient complains of chest pain.