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Drug solubility urinary

As indicated, the ionized form of a drug will be more soluble than the nonionized form in the aqueous fluids of the GIT. The classic studies on the beneficial effects of changing nonionized drugs into salt forms were reported by Nelson for tetracycline [25], and Nelson et al. for tolbutamide [26]. Table 2 combines portions of the data from each study. Urinary excretion of the drug or its metabolite was taken as the in vivo measure of the relative absorption rate for the salt and the nonionized... [Pg.115]

Although demethylation, which occurs in the liver, is normally considered to be a catabolic process, it may result in conversion of an inactive form of a drug to the active form. Thus 6-(methylthio)purine (XXXIX) is demethylated by the rat to 6-mercaptopurine [205]. This demethylation occurs in the liver micro-somes and is an oxidative process which converts the methyl group to formaldehyde [204, 207]. The 1-methyl derivative of 4-aminopyrazolo[3,4-d] pyrimidine (XLI) is demethylated slowly, but 6-mercapto-9-methylpurine (XLII) not at all [208]. The A -demethylation of puromycin (XLlIl) [209, 210], its aminonucleoside (XLIV) [211], and a number of related compounds, including V-methyladenine and V,V-dimethyladenine, occurs in the liver microsomes of rodents [212]. In the guinea-pig the rate-limiting step in the metabolism of the aminonucleoside appears to be the demethylation of the monomethyl compound, which is the major urinary metabolite [213]. The relationship of lipid solubility to microsomal metabolism [214], and the induction of these demethylases in rats by pre-treatment with various drugs have been studied [215]. [Pg.84]

D-penidllamine can promote the elimination of copper (e.g., in Wilson s disease) and of lead ions. It can be given orally. Two additional uses are cystinu-ria and rheumatoid arthritis. In the former, formation of cystine stones in the urinary tract is prevented because the drug can form a disulfide with cysteine that is readily soluble. In the latter, penicillamine can be used as a basal regimen (p. 320). The therapeutic effect may result in part from a reaction with aldehydes, whereby polymerization of collagen molecules into fibrils is inhibited. Unwanted effects are cutaneous damage (diminished resistance to mechanical stress with a tendency to form blisters), nephrotoxicity, bone marrow depression, and taste disturbances. [Pg.302]

Pharmacology Succimer is an orally active, heavy metal chelating agent it forms water soluble chelates and, consequently, increases the urinary excretion of lead. Pharmacokinetics In a study in healthy adult volunteers, after a single dose of 16, 32, or 48 mg/kg, absorption was rapid but variable, with peak blood levels between 1 and 2 hours. Approximately 49% of the dose was excreted 39% in the feces, 9% in the urine, and 1 % as carbon dioxide from the lungs. Because fecal excretion probably represented nonabsorbed drug, most of the absorbed drug was excreted by the kidneys. The apparent elimination half-life was about 2 days. [Pg.375]

Allopurinol, in contrast to the uricosuric drugs, reduces serum urate levels through a competitive inhibition of uric acid synthesis rather than by impairing renal urate reabsorption. This action is accomplished by inhibiting xanthine oxidase, the enzyme involved in the metabolism of hypoxanthine and xanthine to uric acid. After enzyme inhibition, the urinary and blood concentrations of uric acid are greatly reduced and there is a simultaneous increase in the excretion of the more soluble uric acid precursors, xanthine and hypoxanthine. [Pg.445]

Gout is caused by the deposition of crystals of monosodium urate hydrate which are ingested by leucocyctes and trigger the inflammatory response. The biosynthesis of uric acid involves the oxidation of the more soluble compound xanthine (2,6-dihydroxypurine) by xanthine oxidase, and this enzyme is inhibited by allopurinol (187). The treatment of gout also relies on uricosuric drugs to accelerate urinary excretion of uric acid and antiinflammatory drugs to ease the pain and inflammation. [Pg.173]

Tetracyclines are classified as broad-spectrum antibiotics obtained from soil acti-nomycetes. All tetracyclines are slightly bitter solids and are weakly soluble in water. Although tetracyclines develop organism resistance, they are the drugs of first choice in venereal disease, atypical pneumonia, cholera, brucellosis, and plague. Tetracyclines also are used in urinary tract infections, amebiasis, acne, and as prophylaxis against meningitis. [Pg.292]

Several factors suggest the possibility of THC transfer into the milk of humans. Hollister et al (16) found unmetabolized A9-THC in human urines between 0-6 hours after a 30 mg dose. Total urinary THC recovered was 0.005 to 0.01% of dose. We report similar HPLC results in this paper. Plasma A9-THC levels of 100-300 ng/ml have been measured in humans after smoking three 20 mg A9-THC cigarettes. (17) Transfer of drugs from plasma into the milk is facilitated by high lipid solubility of the drug, and A9-THC is a strong lipo-phile. [Pg.134]

CIPROFLOXACIN SODIUM BICARBONATE 1 solubility of ciprofloxacin in the urine, leading to t risk of crystalluria and renal damage t urinary pH caused by sodium bicarbonate can result in 1 ciprofloxacin solubility in the urine If both drugs are used concomitantly, the patient should be well hydrated and be monitored for signs of renal toxicity... [Pg.531]

The primary organ for the regulation of sodium, potassium, calcium, and magnesium is the kidney. An intricate series of physiological sensing elements and hormonal response mechanisms maintains homeostasis. A variety of diuretic drugs can be used to enhance urinary output of various soluble salts, primarily sodium and potassium chloride. Profuse sweating is also a pathway of excretion for soluble salts and occasionally zinc. ... [Pg.3198]

In the distal part of the nephron, urine is concentrated and the likelihood of crystalline precipitation increases substantially, particularly if urinary pH favors decreased solubility. As the urinary concentrating process also involves the counter-current mechanism, solute concentrations in the medullary interstitium can reach values several times higher than tissues elsewhere in the body. Finally during the process of renal excretion, a particular drug may undergo bioactivation resulting in reactive metabolites [2]. [Pg.44]

Sulfadiazine, like other sulfas, has a low urinary solubility, particularly in acid urine. When the urine is alkalinized and pH rises above 7.15, the drug ionizes and forms a soluble salt that is excreted avoiding crystallization. It has been estimated that at a pH of 5.5 about 16 liters of urine will be needed to insure that the sulfadiazine is soluble when excreted following a dose of 4 g per day [5]. Indeed, the urinary solubility of sulfadiazine and its major metabolite, acetylsulfadiazine, are many times higher at a pH of 7.5 than at a pH of 6.5 (sulfadiazine 200 and 28 mg/dl, acetylsulfadiazine 512 and 75 mg/dl, respectively) [30]. The crystals of sulfadiazine and acetylsulfadiazine can be recognized by examining the urine sediment, where they resemble characteristic "sheaves of wheat" [3]. As the crystals transit... [Pg.354]


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See also in sourсe #XX -- [ Pg.76 , Pg.399 ]




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