Common adverse effects of beta2 stimulants include tremors, tachycardia, hypokalemia, hyperglycemia, and lactic acidosis. Here we report a case of a 10-year-old girl who showed adverse effects after ingestion of beta2 stimulants. Two days before admission, she was prescribed one 50-μg tablet of procaterol and one 200-mg tablet of clarithromycin twice a day for her frequent cough. She took one tablet of each; 2 hours later, she developed tachycardia, nausea, and vomiting. At 4.5 hours after ingestion, she visited our hospital. At the time of admission she had tachycardia, abdominal pain, tremor, lactic acidosis, and hyperglycemia, and we treated her for hypokalemia and lactic acidosis. The serum procaterol level was 79.4 pg/mL at 7 hours after ingestion. Many reports have detailed hypokalemia and lactic acidosis as a consequence of long-term oral administration of beta2 stimulants; however, to date, there are few reports that describe the development of side effects after short-term use. Therefore, when prescribing procaterol to children, the possibility of adverse effects should be considered.