Kidneys drug elimination through

Gemfibrozil is absorbed quantitatively from the intestine and is tightly bound to plasma proteins. It undergoes enterohepatic circulation and readily passes the placenta. The plasma half-life is 1.5 hours. Seventy percent is eliminated through the kidneys, mostly unmodified. The liver modifies some of the drug to hydroxymethyl, carboxyl, or quinol derivatives. Fenofibrate is an isopropyl ester that is hydrolyzed completely in the intestine. Its plasma half-life is 20 hours. Sixty percent is excreted in the urine as the glucuronide, and about 25% in feces. 

The primary function of the kidneys is to rid the body of waste materials that are either ingested or produced by metabolism, and to control the volume and composition of the body fluids. The toxins absorbed by the different routes are biotransformed and enter the blood. They are then eliminated through the urine, feces, and air. Since the kidneys receive approximately a quarter of the cardiac output, it is an important organ for the exposure of toxicants and their metabolites. Recent incidents of pet food toxicity and diethylene glycol toxicity indicate that contamination of animal and human food and drugs, respectively, can lead to severe mortahty and morbidity as a result of renal toxicity. 

For drugs eliminated primarily intact through the kidneys, as the renal clearance decreases, t2 will increase (assuming that V j is unchanged). It should be noted that active drug metabolites may also be excreted by the kidney and therefore have a prolonged half-life in renal failure. 

For drugs eliminated primarily intact through the kidneys, as the renal clearance decreases, t2 will in-... 

Drugs which are either water-soluble or get metabolized gradually are mostly eliminated through the kidneys by the aid of these three essential phenomena, viz seeretion, glomerular filtration and tubular reabsorption. For instance, probenecid considerably retards tubular seeretion of penicillin thereby enhaneing its duration of action appreciably. 

Haloperidol is readily absorbed from the gastrointestinal tract. Peak plasma levels occur 2 to 6 hours after ingestion. The drug is concentrated in the liver and CNS. Approximately 15% of a given dose is excreted in the bile, and approximately 40% is eliminated through the kidney. Figure 22.8 shows the typical oxidative metabolic pathway of butyrophenones as exemplified by haloperidol (41). 

It is, therefore, clear that a drug eliminated in urine may undergo one, all or any combination of the processes of glomerular filtration, tubular secretion or reabsorption. However, these mechanisms usually produce the net effect of removing a constant fraction of a drug presented to the kidneys through renal arterial blood. 

The elimination of a drug is its removal from the body, either by chemical modification through metabolism or by removal from the body through the kidney, the gut, the lungs or the skin. 

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