Drug design involves discovering new medications based on specific biological targets. It relies on structure-activity relationships, SAR, or quantitative structure-activity relationships, QSAR.

SAR studies the relationship between a drug's chemical structure and biological activity. It focuses on how structural modification of a drug can influence its affinity, efficacy, and potency.

Affinity denotes the strength of interaction between a drug and its target receptor. Efficacy measures the maximum achievable therapeutic effect, while potency indicates the drug quantity needed to produce an effect.

QSAR uses mathematical models and computational techniques to correlate a drug's chemical structure with its biological activity.

SAR was used in the development of beta-blockers to treat high blood pressure. First-generation beta blockers non-selectively blocked β₁ and β₂ adrenergic receptors, leading to undesirable side effects like bradycardia, peripheral vasoconstriction, and bronchoconstriction.

However, SAR analysis helped enhance β₁ receptor selectivity. For example, metoprolol is a selective β₁ blocker with reduced side effects.