Dosage Regimen: Individualization

Pharmacokinetic variability refers to differences in how the body processes drugs, while pharmacodynamic variability describes differences in how individuals respond to a drug, even at the same concentration.

Drug responses vary due to factors such as genetics, disease, and age, causing intersubject variability, where different patients experience distinct pharmacological responses to the same drug dose.

In contrast, intrasubject variability occurs when the same individual exhibits differences in plasma drug levels upon receiving the same medication on different occasions.

Individualized dosing tailors medication to each person's unique response to optimize treatment outcomes and minimize risks.

Key factors in individualized regimens include dose strengths, the degree of intersubject variability, and the therapeutic index, among others.

For instance, drugs with a narrow therapeutic index require precise dosing to prevent fluctuations in plasma drug concentrations, which could lead to adverse effects or therapeutic failure.

However, GRAS and over-the-counter drugs typically require less stringent individualization.