MEDICAL ANIMATION TRANSCRIPT: Drug metabolism is the chemical conversion of drugs into water soluble compounds that can be excreted by the body. Drug metabolism mainly takes place in the liver, while excretion mainly takes place in the kidneys. Following drug administration, drugs must pass through tightly packed cells, crossing cell membranes to reach their sites of action. Usually drugs are lipophilic or fat soluble compounds, and cell membranes are composed of phospholipids, so drugs are able to cross them. However, for excretion by the kidneys, it's necessary to convert drugs to water soluble or hydrophilic compounds. Drugs are usually administered orally or parenterally. Parenteral drugs bypass the digestive tract. Parental routes include injection, transdermal patches, lotions, inhalants, and suppositories. If injected, the drugs reach general circulation quickly and have an immediate effect. If taken orally, drugs must pass through the cells of the gastrointestinal tract. Drugs ...