TRC: Half-life in pediatrics

Half-life

Due to a slower biotransformation most half-lives of drugs are increased. Also a lower renal excretion rate contributes to an extended half-life. On the other hand, much more free drug is available in the plasma of young children and thus more drug can be eliminated. All these factors together determine the half-life. A significant change in one of the factors can lead to shortening or prolongation of the half-life.

Half-life = (0.693 x volume of distribution) / clearance

Example:

The elimination half-life of theophylline varies during early life and childhood. In premature neonates the t1/2 is 30 hours. In neonates the half-life is 24 hours. During childhood the half-life is much lower: only 3.5 hours for children from 1 to 9. So, for this age group, increased frequency of administration of theophylline is necessary. Towards the adult life the t1/2 increases again to 8 hours.

Drug A has a longer half-life than drug B. This means that the concentration of drug A in the body is higher than that of drug B when both drugs are given intravenously at the same time.

Extra info: The concentration of each drug depends on the starting dose of that drug. If B was given at a very high dose, its concentration would remain higher than drug A’s concentration until A has been fully eliminated from the system.

Option explanation:

true

false

Generally speaking, the half-lives of corticosteroids compared with those in other drugs are:

Extra info: Corticosteroids are lipophilic molecules and thus are hard to eliminate from the body. Corticosteroids can stay in the body for weeks to months after the last administration of the drugs.

Option explanation:

Longer

Shorter

The same

None of the above

Half-life

Half-life

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