Understanding the kinetics of drug elimination is paramount for the design of appropriate dosage regimens. For most drugs, some minimum concentration is needed to achieve a therapeutic benefit. However, toxic effects may occur if the concentration of the drug becomes too high. The challenge therefore is to design a dosage schedule which maintains the concentration above the minimum therapeutic concentration, but below the threshold for toxic effects. Furthermore, the schedule should also be convenient and feasible for the patient to follow. A final consideration is how long it takes to reach the therapeutic concentration. For certain drug therapies it is essential that it be obtained quickly. Designing these schedules therefore requires a quantitative description of drug concentration in patients as a function of time for different dosage regimens. The elimination of many drugs from the body follows ideal first order kinetics, meaning that their rate of elimination is proportional to their concentration.
In this article I develop equations to describe the first order elimination of drugs from the body. This was done for a variety of commonly used dosage regimens: single discrete doses, periodic discrete doses, and continuous administration. In addition to general equations for the concentration as a function of time, the properties of the steady state and the rate of steady state attainment are quantitatively described. These equations facilitate the precise and efficient design of dosage regimens for new drugs to achieve whatever properties are desired clinically. The full article is available as a pdf document below:
In this article I develop equations to describe the first order elimination of drugs from the body. This was done for a variety of commonly used dosage regimens: single discrete doses, periodic discrete doses, and continuous administration. In addition to general equations for the concentration as a function of time, the properties of the steady state and the rate of steady state attainment are quantitatively described. These equations facilitate the precise and efficient design of dosage regimens for new drugs to achieve whatever properties are desired clinically. The full article is available as a pdf document below:
| first_order_drug_elimination_kinetics.pdf |
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