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.

The time required to achieve steady state is dependent on the drug half life. It takes about 5-6 half lives to achieve steady state. The steady state concentration during constant rate iv infusion is directly proportional to the infusion rate and inversely proportional to the total body clearance of the drug.

The volume of distribution is the apparent volume in which the drug can be distributed in. It is the factor that relates the amount of drug in the body to the concentration of the drug in the sampling site. It is n. an actual volume, however it is a hypothetical volume determined by the dg distribution behavior.

The volume of distribution ranges from 3-5 liters to more than 25 L/kg. Drugs with higher affinity for tissues, have higher volume of distribution.