May increase risk of asthma-related deaths. Bronchospasm might occur. Immediate hypersensitivity reactions (urticaria, angioedema, rash, bronchospasm) may develop. Use with caution in cardiovascular disease (β-agonists may cause elevation in blood pressure, heart rate and may also increase risk of arrhythmias and prolong QTc interval), diabetes mellitus (β~2~-agonists may increase serum glucose), hepatic impairment (prolonged systemic clearance), hyperthyroidism (may stimulate thyroid activity), hypokalemia (β~2~-agonists may decrease serum potassium), or in seizure disorders (β~2~-agonists may result in CNS stimulation/excitation). Should not be initiated in patients with acutely deteriorating chronic obstructive pulmonary disease or combined with other long-acting β~2~-agonists.