Kidneys drug excretion

Oxytetracycline is also one of the most frequently used antibiotics in fish farming. Oxytetracycline residues exceeding the 0.1 ppm tolerance level were detected in raw catfish fillets 18 h after oral administration at a dosage of 37.5, 75, or 150 mg/kg fish for 10 days (238). Residues were highest in liver, followed by muscle, plasma, and kidney. Drug excretion was temperature dependent higher residue levels could be detected at lower temperatures. In rainbow trout... 

The kidneys are located on the posterior part of the abdomen on either side of the spine, below the diaphragm, and behind the liver and stomach. They are bean-shaped and weigh approximately 150 grams (0.33 lb) each. The primary function of the kidneys is excretion. They work to excrete waste products through a series of steps involving glomerular filtration, secretion, and reabsorption. The kidneys also have several endocrine (e.g., production of erythropoietin and renin) and metabolic (e.g., vitamin D activation and drug metabolism) functions. 

Hypomagnesemia is usually associated with disorders of the intestinal tract or kidneys. Drugs (e.g., aminoglycosides, amphotericin B, cyclosporine, diuretics, digitalis, cisplatin) or conditions that interfere with intestinal absorption or increase renal excretion of magnesium can cause hypomagnesemia. 

Acetylated MS-222 was found in much higher concentrations in the urine than in the blood of rainbow trout. This suggests that the kidney concentrated the drug metabolite, or that MS-222 was acetylated in the kidney and excreted in the urine (28). Weber (31) stated that acetylation of p-aminobenzoic acid and sulfamethazine is catalyzed by most of the tissues in the body. He showed that in rabbits the acetylation of these amines by the kidney of rabbit is a small percentage of the total acetylation capability, but that the kidney is involved in this biotransformation. 

Since approximately 130 mL of plasma water is filtered across the porous glomerular capillary membranes each minute (190 L/day), the kidney is admirably suited for its role in drug excretion. As the ultrafiltrate is formed, any drug that is free in the plasma water, that is, not bound to plasma proteins or the formed elements in the blood (e.g., red blood cells), will be filtered as a result of the driving force provided by cardiac pumping. 

Pharmacokinetics Rapidly absorbed. Extensive metabolism in liver and kidneys. Minimal excretion in urine as unchanged drug. Half-life 36 min,... 

Excretion is tlie process by which the parent drug and its metabolites are removed from the body fluids before elimination occurs. The most important site of drug excretion is die kidney. Extrarenal sites of excretion include die liver, lung, mammary gland, sweat gland, salivary glands, and intestinal mucosa. 

Penicillin G is readily absorbed into the bloodstream where it is partially bound to blood proteins. During the first few hours after injection of penicillin G, residue concenttation was higher in the blood than in other tissues and milk, except liver and kidney. Thereafter, there was a more rapid drug clearance from the blood and the concentrations in tissues and milk became higher. Penicillin G was rapidly cleared from the blood through the kidneys and excreted unchanged, almost entirely into the urine. 

The molecular weight or size of an optimal delivery system in vivo is imposed by the physiology of circulation and excretion. The lower limit of the molecular weight is about 30 kDa because the microtubular cells in the kidney readily excrete hydrophilic molecules whose molecular weight is 30 kDa or less.23 In fact, this is the major route of elimination for many small-molecule drugs after they are transformed into more hydrophilic metabolites. Therefore, a drug delivery system should have a combined molecular weight of 30 kDa to avoid such a quick renal clearance. 

The elderly are also prone to toxicity from numerous drugs, including cardiac glycosides. A dose of digitoxin, which may be totally therapeutic and innocuous at the age of 60, may produce severe toxicity and even death at the age of 70. The abilities of the liver to metabolize drugs and of the kidney to excrete drug metabolites decline with aging. 

All drugs are ultimately removed from the body, either in the form of their metabolites or in their unchanged form, by excretory organs (mainly the kidneys) and excreted in the urine (although in some instances, excretion may be via the biliary route). Compromised renal function may effect the PK of the drugs if urinary excretion is a substantial part of the overall elimination. 

The kidneys excrete a variety of waste products produced by metabolism, including the nitrogenous wastes urea (from protein catabolism) and uric acid (from nucleic acid metabolism). The kidneys also excrete many drugs or their metabolites, in particular those that are hydrophilic, have a small volume of distribution and a low degree of protein binding. 

The kidneys will excrete excess acid equivalents in the urine. At acidic pH, LSD will become protonated and therefore no longer slip back across the tubule epithelium into the circulation this will lead to accelerated elimination of LSD. We here have another example of the principle of non-ionic diffusion , which we have previously discussed in the context of drug absorption. 

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