投与量と反応関係: 選択性と特異性

Different types of receptors are expressed throughout the body. The interaction of these receptors with drug molecules may lead to a pharmacologic response.

Drug–receptor interactions are characterized by selectivity and specificity.

Drug specificity is the ability of a drug to interact with only a specific target.

For example, in the parietal cells of the stomach, omeprazole inhibits the proton pump and decreases acid secretion into the stomach lumen.

In contrast, drugs like amiodarone have low specificity as they interact with multiple targets in the body, including receptors, enzymes and ion channels. Such off-target interactions can lead to several adverse effects beyond the drug's primary action.

Drug selectivity describes the strong preference of a drug for its intended receptor over other receptors.

For instance, consider two β-adrenergic agonists, isoprenaline and salbutamol.

As isoprenaline is a nonselective β agonist, it can stimulate β-1 receptors of the heart and β-2 receptors of the bronchioles. This increases the heart rate and relaxes the bronchial muscles.

In comparison, salbutamol is a selective β agonist with a higher affinity for the β-2 receptors, causing bronchodilation.