Understanding Drug Action

Drug Targets & Mechanisms

Drugs exert their effects by interacting with specific targets within the body. These ‘targets’ are typically proteins – enzymes, receptors, ion channels – that play a crucial role in biological processes.

Receptor drugs bind to receptors, triggering a cascade of events. Enzyme inhibitors block enzyme activity, while modulator drugs alter receptor sensitivity.

Pharmacokinetics: ADME

The study of pharmacokinetics (PK) examines what the body does to a drug. This involves four key processes: Absorption, Distribution, Metabolism, and Excretion (ADME).

Absorption is how quickly a drug enters the bloodstream. Distribution describes where it goes in the body. Metabolism alters the drug’s structure, often rendering it inactive. Finally, excretion removes the drug and its metabolites.

Drug Concentration = Absorption Rate - Elimination Rate + Input

Drug Interactions

Drugs can interact with each other in complex ways, altering their effects. These interactions can be due to shared metabolic pathways or direct chemical reactions.

Pharmacokinetic interactions (e.g., one drug slowing another’s absorption) and pharmacodynamic interactions (where drugs have combined effects) are common.

Therapeutic Drug Monitoring

In some cases, therapeutic drug monitoring is used to ensure that a patient’s blood concentration of a drug falls within the desired range.

This helps optimize dosing and minimize adverse effects. Factors like age, kidney function, and liver enzymes can significantly influence drug levels.

Drug Level = Dose x (Absorption Rate - Elimination Rate)

Frequently asked questions

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