Knowledge of drug distribution characteristics is important in determining the dose. Important issues concerning distribution are: a drug's volume of distribution (Vd), solubility in fat, degree of ionisation of the drug, level of plasma protein binding, and tissue blood flow.

In this graphic a comparison is made between the percentages of water

and fat in the total body composition in children and adults. Neonates have a relatively high fluid level (also extracellular fluids) and a very low level of fat.

In general, distribution volumes of drugs are higher (since many are hydrophilic) in young children and gradually decrease towards the adult age, but with variations and exceptions.


Due to the high percentage of water in body composition of neonates, the topical administration of hydrophilic drugs would be: