Most common side effect of salbutamol is:
**Core Concept**
Salbutamol is a short-acting β2-adrenergic receptor agonist (SABA) used primarily for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease (COPD). Its mechanism of action involves binding to β2-adrenergic receptors in the lungs, leading to bronchodilation.
**Why the Correct Answer is Right**
The most common side effect of salbutamol is due to its systemic effects on β2-adrenergic receptors, which are also found in other parts of the body, such as the heart and blood vessels. The binding of salbutamol to these receptors can cause a decrease in peripheral vascular resistance, leading to a decrease in blood pressure and an increase in heart rate. This effect is known as a "rebound" or "tachyphylaxis" phenomenon, where the body adapts to the continuous stimulation of β2-adrenergic receptors by developing a tolerance to the drug.
**Why Each Wrong Option is Incorrect**
**Option A:** Tachycardia is a possible side effect of salbutamol, but it is not the most common side effect. Tachycardia occurs due to the increase in sympathetic tone caused by the stimulation of β2-adrenergic receptors in the heart.
**Option B:** Tremors are a less common side effect of salbutamol, and are thought to be caused by the stimulation of β2-adrenergic receptors in the skeletal muscle.
**Option C:** Chest pain is a rare side effect of salbutamol, and is thought to be caused by the increase in heart rate and blood pressure, which can lead to angina in patients with pre-existing coronary artery disease.
**Clinical Pearl / High-Yield Fact**
The most common side effect of salbutamol can be minimized by using a spacer device when administering the medication, which helps to deliver the medication directly to the lungs and reduces the amount of medication that is absorbed systemically.
**Correct Answer: A. Tachycardia. Tachycardia is a common side effect of salbutamol.**