Drug excretion
Drug excretion
Drug excretion refers to the elimination of drugs from the body. Most drugs are excreted by the kidneys and leave the body through urine. Drugs can also be excreted through the lungs, exocrine (sweat, salivary, or mammary) glands, skin, and intestinal tract.
Halflife = half the drug The halflife of a drug is the time it takes for onehalf of the drug to be eliminated by the body.
Factors that affect a drug’s half life
rate of absorptionmetabolismexcretion.
Knowing how long a drug remains in the body helps determine how frequently it should be administered.
A drug that’s given only once is eliminated from the body almost completely after four or five halflives.
A drug that’s administered at regular intervals, however, reaches a steady concentration (or steady state) after about four or five halflives.
Steady state occurs when the rate of drug administration equals the rate of drug excretion.