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Receptor Occupancy

Meaning

Receptor occupancy is a core pharmacological concept that quantitatively describes the proportion of specific cellular receptors in a target tissue that are physically bound by an administered drug or an endogenous hormone ligand at any given moment. This measurable parameter is a direct and critical determinant of the magnitude of the resulting biological response, as therapeutic efficacy generally correlates with the number of receptors occupied. Achieving high occupancy is often necessary for maximal therapeutic effect, but it can also escalate the risk of adverse effects if the drug lacks selectivity or if the receptor is excessively stimulated. Clinicians rely on sophisticated pharmacokinetic and pharmacodynamic models to predict and optimize this crucial parameter.