Clayton’s Basic Pharmacology For Nurses Practice Exam

The main idea is how the body eliminates drugs, with the kidneys handling the majority of excretion. Most drugs are cleared from the body primarily by the kidneys into the urine. This happens as the kidneys filter freely circulating drug through the glomeruli, then may actively secrete additional drug into the filtrate in the proximal tubule, and, depending on a drug’s properties, may be reabsorbed later in the nephron. Factors like molecular size, polarity, protein binding, and the drug’s ionization state influence how much is excreted renally. For example, altering urine pH can change ionization and promote “ion trapping” to enhance excretion of weak acids or bases. While some drugs are eliminated via the GI tract through bile into feces, or by other routes such as the lungs for volatile substances or tiny amounts through sweat, these are not the primary pathways for most drugs.