Intrinsic activity

Intrinsic activity refers to the inherent ability of a drug or other substance to produce a physiological effect. This term is often used in pharmacology to describe the relative ability of a drug to bind to a receptor and initiate a response.

Definition

Intrinsic activity is defined as the relative ability of a drug-receptor complex to produce a maximum functional response. This is often expressed as a proportion of the drug's maximal efficacy. Drugs with high intrinsic activity are known as full agonists, while those with lower intrinsic activity are referred to as partial agonists.

Measurement

The intrinsic activity of a drug can be measured using various bioassay techniques. These methods typically involve observing the response of a biological system (such as a cell or tissue) to the drug, and comparing this to the response produced by a reference drug with known intrinsic activity.

Factors Influencing Intrinsic Activity

Several factors can influence the intrinsic activity of a drug, including its chemical structure, the nature of its receptor, and the presence of other substances that may interact with the drug or receptor.

Clinical Significance

Understanding the intrinsic activity of a drug is important in clinical pharmacology, as it can help predict the drug's potential therapeutic effects and side effects. For example, drugs with high intrinsic activity are often more potent and have a greater risk of producing side effects, while those with lower intrinsic activity may be less potent but also less likely to produce side effects.

See Also

• Pharmacodynamics
• Pharmacokinetics
• Receptor (biochemistry)
• Agonist
• Antagonist