💊 Long-Acting Beta-2 Agonists (LABA)

Long-acting beta-2 agonists (LABAs) are bronchodilator medications that provide sustained relaxation of airway smooth muscle. They are used as 'maintenance' therapy in chronic respiratory conditions.

LABAs selectively stimulate beta-2 adrenergic receptors in the bronchial smooth muscle, similar to SABAs. However, their molecular structure allows them to bind to the receptor for a prolonged period or to remain in the cell membrane, providing a longer duration of action. This leads to sustained bronchodilation over 12-24 hours.

LABAs are indicated as maintenance therapy for asthma, always in combination with an inhaled corticosteroid (ICS), never as monotherapy. They are also used as maintenance bronchodilator therapy in chronic obstructive pulmonary disease (COPD) to improve symptoms and reduce exacerbations. They can be used alone or in combination with other bronchodilators in COPD.

LABAs are contraindicated as monotherapy in asthma due to an increased risk of severe asthma exacerbations and asthma-related death. They should always be used in combination with an ICS in asthma. Caution is advised in patients with severe cardiovascular disease, arrhythmias, or uncontrolled hyperthyroidism.

Common side effects are similar to SABAs but may be more persistent, including tremor, palpitations, and headache. Muscle cramps and dizziness can also occur. Rarely, paradoxical bronchospasm can occur. In asthma, the risk of severe exacerbations is increased if used without an ICS.

Patients should be monitored for the effectiveness of symptom control and any worsening of respiratory function. Regular assessment of inhaler technique is crucial. In patients with cardiovascular comorbidities, heart rate and blood pressure should be monitored.

When prescribing, always confirm the patient's allergy status. For asthma, ensure an ICS is prescribed concurrently or as part of a combination inhaler. Counsel patients that LABAs are for regular, long-term control and not for immediate symptom relief. Advise them to continue using their SABA for acute symptoms.

LABAs (e.g., salmeterol, formoterol, indacaterol) provide long-lasting bronchodilation. In asthma, they must always be co-prescribed with an ICS due to safety concerns. In COPD, they are used for symptom relief and exacerbation reduction. They are maintenance, 'preventer' medications, not for acute relief.

SBAs frequently test the crucial point that LABAs must never be used as monotherapy in asthma; they always require an accompanying ICS. Questions may also focus on their role in COPD as maintenance therapy. Distinguishing their long duration of action from SABAs and their use as 'preventers' rather than 'relievers' is a common theme.