The dosing interval is the period of time between administration of doses.

The steady state is the condition when the rate of drug administration is equal to the rate of drug elimination.

When the drug is administered as a constant rate IV infusion, there will be one steady state concentration as long as the rate of administration and the rate of elimination do not change.

When drug administration involves repeated doses, the drug concentration-time profile during each of the dosing intervals ( τ ) will be identical at steady state. This means that the maximum, the minimum, and the average concentrations during each dosing interval will be similar at steady state.

The first-order elimination rate constant is the rate constant for the elimination of the drug from the body. The elimination rate constant and the half life are dependent on the total body clearance and the volume of distribution of the drug.

This rate constant represents drug elimination through all routes of drug elimination such as metabolism, renal excretion, and other routes.

The first-order elimination rate constant has units of time^-1.

The choice of dosing interval can help the patient and also the health care team to remember the time for drug administration. Dosing intervals in which the time for drug administration is the same time of the day are much better than when the time of drug administration changes every day. For example:

Drugs given every 6 hr ( 6:00 AM, 12:00 AM, 6:00 PM, and 12:00 PM)

Drugs given every 8 hr ( 8:00 AM, 4:00 PM, and 12:00 PM)

Drugs given every 12 hr ( 8:00 AM, and 8:00 PM )

Practical dosing intervals are : 6 hr, 8 hr, 12 hr, 18 hr, 24 hr, 48 hr, 72 hr etc.