Gastric excretion

B. Pharmacokinetics. PCP is rapidly absorbed by inhalation or ingestion. The volume of distribution (Vd) is about 6 L/kg. The duration of clinical effects after an overdose is highly variable and ranges from 11-14 hours in one report to 1-4 days in another. PCP is eliminated mainly by hepatic metabolism, although renal and gastric excretion account for a small fraction and are pH dependent. (See also Table 11-59.) Ketamine is well absorbed after snorting, in-... 

Metabolic alkalosis is characterized by an increased arterial pH, a primary increase in the HCOf concentration, and a compensatory increase in the PaC02. Patients will always hypoventilate to compensate for metabolic alkalosis—even if it results in profound hypoxemia. For a metabolic alkalosis to persist there must concurrently be a process that elevates serum HC03 concentration (gastric or renal loss of acids) and another that impairs renal HC03 excretion (hypovolemia, hypokalemia, or mineralocorticoid excess). The etiologies of metabolic alkalosis are listed in Table 25-5. 

The majority of evidence supporting the pH-partition hypothesis is from studies of gastrointestinal absorption, renal excretion, and gastric secretion of drugs [11]. While correlation between absorption rate and pKa was found to be consistent with the pH-partition hypothesis, deviations from this hypothesis were often reported [12]. Such deviations were explained by the existence of a mucosal unstirred layer [13,14] and/or a microclimate pH [15]. 

Excretion of -hexane after oral exposure in humans can be inferred from the appearance of -hexane in exhaled air and 2,5-hexanedione in urine of volunteers receiving 0.24 or 0.81 mg/kg via a gastric feeding tube (Baelum et al. 1998). No studies were located regarding excretion of -hexane or -hexane metabolites following oral exposure to -hexane in animals. 

The interaction of /2-hexane with toluene and trichloroethylene has also been examined in volunteers (Baelum et al. 1998). Exposure in these experiments was via a gastric feeding tube at controlled rates equivalent to what the authors stated would be delivered to the liver by inhalation exposure at Danish occupational exposure limits (50 ppm /7-hexane. 50 ppm toluene, and 30 ppm trichloroethylene). Coexposure to toluene and trichloroethylene slightly increased the area under the curve (AUC) representing concentration versus time for end exhaled /2-hexane air concentration, but urinary excretion of 2,5-hexanedione was unchanged. The only statistically significant interaction observed with /2-hexane was an 18% decrease in the urinary excretion of hippuric acid, a toluene metabolite. 

Theory Cortisol (or hydrocortisone) was introduced in the year 1951, for the treatment of rheumatoid arthritis. It has a significant effect on protein metabolism. It also exerts widespread effects on carbohydrates, lipid and protein synthesis (or anabolism). The cardinal side effects such as excessive potassium excretion and sodium retention, enhanced gastric acidity, oedema, psychosis and negative nitogen balance are some of the exaggerated manifestations of the normal metabolite functions of cortisol. 

The human body has a number of different pH environments. For example, blood plasma has a rigorously controlled pH of 7.4 (see Box 4.9), the gastric juice is usually strongly acidic (pH from about 1 to 7), and urine can vary from about 4.8 to 7.5. It is possible to predict the qualitative effect of pH changes on the distribution of weakly acidic and basic dmgs, especially in relation to gastric absorption and renal excretion ... 

Agents in this class are omeprazole, lansoprazole, pantoprazole and rabeprazole. Esomeprazole is the S-enantiomer of omeprazole. After ingestion of gastric acid resistant formulations they are rapidly and more or less completely absorbed. Bioavailability may be reduced if administered with food or antacids. Elimination is via metabolism in the liver and the renal excretion of inactive metabolites. The elimination half-live is very variable, however, as explained above, not related to the duration of action. 

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