Drug elimination is the process by which pharmaceutical substances are removed from the body. All drugs are eventually eliminated from the body, although there are various pathways that may be involved in the process. Some drugs undergo metabolism before being excreted, whereas other drugs are largely eliminated intact in the original dosage form. Show
The kidneys are responsible for the majority of excretion of water-soluble substances. The biliary system can also excrete drugs that are not reabsorbed from the gastrointestinal tract. In most cases, the amount of excreted drug in the intestine, saliva, sweat, breast milk and lungs is negligible. However, some volatile anesthetics can be exhaled via the lungs. Also, even small drug concentrations in breast milk of lactating women may affect a breastfeeding infant. Renal ExcretionApproximately 20% of the plasma is filtered through the glomerulI into the kidney ultrafiltrate. Most of the water and electrolytes is then passively or actively reabsorbed into blood from the renal tubules, and are not excreted in the urine. In contrast, polar compounds, such as most drug metabolites, are not able to diffuse back into the circulation so easily, and are excreted from the body in the urine. The renal excretion of drugs typically decreases with age, and the renal clearance of an individual at the age of 80 is considered to be approximately half of what it was at the age of 30. As a result, drugs that are predominantly excreted by the kidneys may require to be administered at half the dose for elderly patients, to reduce the risk of adverse effects. Various factors can affect renal excretion, such as:
Biliary EliminationSome drugs and metabolites can be excreted in the bile because they cross the biliary epithelium via active secretory transport. When the concentration of the drug in the body is high, the secretory transport carriers can become saturated and the excretion reaches an upper limit. Drugs that are excreted through bile are large, with a molecular weight <300 g/mol, and usually have polar and lipophilic groups. Smaller molecules are usually excreted in the kidneys. Other Forms of EliminationSome drugs can be excreted to varying extents in the saliva, tears, feces, sweat, breast milk and by exhalation from the lungs. However, this usually only occurs in small amounts. The excretion of drugs in breast milk can be a concern for lactating mothers because of the exposure this causes to infants who are breastfeeding. Pharmacokinetic Parameters for ExcretionThe pharmacokinetic parameters for drug excretion include:
Pharmacokinetics 5 - Excretion References
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Last Updated: Feb 27, 2019  Written by Yolanda SmithYolanda graduated with a Bachelor of Pharmacy at the University of South Australia and has experience working in both Australia and Italy. She is passionate about how medicine, diet and lifestyle affect our health and enjoys helping people understand this. In her spare time she loves to explore the world and learn about new cultures and languages. CitationsPlease use one of the following formats to cite this article in your essay, paper or report:
Suggested ReadingWhat is the most important organ for excretion of drugs and their metabolites?Although many sites of metabolism and excretion exist, the chief organ of metabolism is the liver, while the organ primarily tasked with excretion is the kidney. Any significant dysfunction in either organ can result in the accumulation of the drug or its metabolites in toxic concentrations.
What organ is the most important site of drug metabolism?Most drugs must pass through the liver, which is the primary site for drug metabolism. Once in the liver, enzymes convert prodrugs to active metabolites or convert active drugs to inactive forms. The liver's primary mechanism for metabolizing drugs is via a specific group of cytochrome P-450 enzymes.
What area of the body is most responsible for drug excretion?Most drugs, particularly water-soluble drugs and their metabolites, are eliminated largely by the kidneys in urine. Therefore, drug dosing depends largely on kidney function. Some drugs are eliminated by excretion in the bile (a greenish yellow fluid secreted by the liver and stored in the gallbladder).
What organ is primarily responsible for drug medication excretion quizlet?The kidneys are the primary organ system responsible for drug elimination.
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The is the most important organ for excretion of drugs and their metabolites Quizlet
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