Dose proportionality

Dose Proportionality is a fundamental concept in pharmacokinetics, which refers to the relationship between the dose of a drug administered and the resulting concentration of the drug in the body.

Definition

Dose proportionality is defined as a linear relationship between the dose of a drug and its plasma concentration or the amount of drug in the body. In other words, if the dose of a drug is doubled, the concentration of the drug in the body should also double, assuming dose proportionality.

Importance

Understanding dose proportionality is crucial in drug development and clinical pharmacology. It helps in predicting the behavior of a drug in the body, determining the appropriate dosage for patients, and assessing the safety and efficacy of new drugs.

Factors Influencing Dose Proportionality

Several factors can influence dose proportionality, including drug absorption, drug distribution, and drug metabolism. For instance, if a drug is not fully absorbed or if it is extensively metabolized, the relationship between the dose and the drug concentration in the body may not be proportional.

Assessment of Dose Proportionality

Dose proportionality is typically assessed in clinical trials using statistical methods. The most common method is the power model, which involves plotting the dose of a drug against its plasma concentration on a log-log scale. If the relationship is linear, the drug is considered dose-proportional.

Limitations

While dose proportionality is a useful concept, it has its limitations. It assumes that the body's processes for absorbing, distributing, metabolizing, and excreting the drug do not change with the dose, which is not always the case. Moreover, it does not account for individual variations in these processes.

See Also

• Pharmacokinetics
• Drug development
• Clinical pharmacology