Absorption (pharmacokinetics)

Absorption (pharmacokinetics)

Absorption in pharmacokinetics refers to the process by which a drug or other substance moves from the site of administration to the bloodstream. This process is crucial in determining the onset, intensity, and duration of a drug's effect.

Mechanisms of Absorption

There are several mechanisms by which drugs are absorbed into the body. These include:

• Passive diffusion: This is the most common mechanism of drug absorption. It involves the movement of drug molecules from an area of high concentration (the site of administration) to an area of low concentration (the bloodstream).

• Facilitated diffusion: In this process, carrier proteins in the cell membrane assist in the movement of drug molecules across the membrane.

• Active transport: This mechanism involves the use of energy to move drug molecules against a concentration gradient.

• Endocytosis and exocytosis: These processes involve the engulfing of drug molecules by the cell membrane and their subsequent release into the cell or extracellular space, respectively.

Factors Affecting Absorption

Several factors can affect the rate and extent of drug absorption. These include:

• Drug formulation and dosage form: The physical and chemical properties of the drug and its formulation can significantly impact absorption.

• Route of administration: The path by which a drug is introduced into the body can influence its absorption. For example, drugs administered orally must survive passage through the gastrointestinal tract, which can affect their absorption.

• Physiological factors: Individual characteristics such as age, sex, body weight, and health status can also influence drug absorption.

Clinical Significance

Understanding the absorption process is critical in pharmacotherapy as it helps in determining the dosage regimen and the route of administration for a drug. It also plays a key role in predicting the drug's bioavailability, which is the proportion of the administered drug that reaches the systemic circulation.