Beta-2 agonists are medicines used in the treatment of asthma, COPD and hyperkalemia. Here, we review the primary drug members, how they work, and what side effects and drug interactions the medicines are linked to.
Beta-2 agonists are primarily used to treat respiratory disorders.
For example, they are used to treat:
In the indications above, we referred to “short-acting” and “long-acting” drugs.
That’s because beta-2 agonists are broadly divided into the following three classes:
Note: albuterol is USAN; whereas salbutamol is INN.
The duration of effect determines what medicine is used for immediate, “as required”, relief, and what medicine is used for long-term maintenance.
Beta-2 agonists trigger smooth muscle relaxation; relaxing bronchial smooth muscle.
Beta-2 receptors are not just found in the bronchi, though. They are also found in the GI tract, uterus and throughout blood vessels.
The beta-2 receptor is a G-protein coupled receptor which, upon activation, triggers a signalling cascade that leads to smooth muscle relaxation; enhancing the passage of air throughout respiratory passages.
Beta-2 agonists also stimulate sodium-potassium ATPase pumps. This is what contributes to their potassium-lowering effects. Beta-2 agonism encourages potassium to move from the extracellular compartment to the intracellular compartment – reducing potassium levels in the body.
This makes beta-2 agonists an effective short-term treatment option (not least because therapeutic predictability is not reliable) in hyperkalemic emergencies.
Side effects with beta-2 agonists include:
Very rarely, beta-2 agonists are associated with pulmonary edema and arrhythmias.
Long-acting beta-2 agonists can cause muscle cramps.
When we talk about the clinical pharmacology of beta-2 agonists, we need to think about the following factors:
Beta-2 agonists are important medicines in the treatment of asthma and COPD. Patients should be informed of the correct technique when using an inhaler; with the technique and inhaler checked at each consultation.