All nondepolarizing blockers are polar compounds with two or more quaternary amines. When given orally, these drugs cannot cross the cell membrane and are minimally absorbed by the intestinal villi. So they are administered intravenously. These blockers are rapidly distributed via blood to muscles, causing neuromuscular blockade. Most nondepolarizing blockers are not metabolized, and their actions are terminated by redistribution to the liver and kidneys. The duration of the blockade depends on the drug's elimination half-life, which is the time taken to reduce the initial drug concentration to half. Some drugs are excreted unchanged in the urine. These drugs have a longer half-life and action duration than drugs that are metabolized and eliminated in the liver. The liver metabolizes steroidal relaxants into 3-hydroxy, 17-hydroxy, or 3,17-dihydroxy products. Other drugs remain unchanged and are excreted through the bile.