Clinical pharmacy
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The accuracy of creatinine clearance (CLcr) determinations obtained from urine collections of less than 24 hours duration and the cyclical variation in creatinine excretion were studied in 10 critically ill patients with trauma or postoperative complications. Data from patients who received drugs or had diseases known to influence creatinine production or interfere with assay methods were excluded. Twelve consecutive two-hour urine collections and midpoint blood samples were obtained for each patient. ⋯ Mean differences between each 2-hour interval and the 24-hour interval were not significant for the 12 collection intervals. In critically ill trauma or postsurgical patients, the 24-hour CLcr can be estimated from an 8-hour urine collection if a deviation of up to 20% from the 24-hour value is clinically acceptable. No significant cyclical variation in creatinine excretion over 24 hours was found.
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An evaluation and comparison of the accuracy of six published methods for estimating creatinine clearance from serum creatinine concentration in children are presented. The medical records of 59 patients were reviewed. The patients ranged from 1 to 18 years in age and had one or more 24-hour urine creatinine determinations completed. ⋯ The method of Traub and Johnson also showed an equal tendency to overestimate and underestimate creatinine clearance. This method performed well regardless of the patients' weight, sex, or age; the method was not as accurate in children less than 107 cm in height. It is concluded that the method of Traub and Johnson for estimating creatinine clearance from serum creatinine concentration is the most accurate and nonbiased of the evaluation methods.
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The pharmacokinetic disposition of aminoglycosides in critically ill patients with sepsis was studied. In an open-label study of the disposition of gentamicin and tobramycin, individualized pharmacokinetic values of 100 critically ill patients in the surgical intensive-care unit were compared with those of a concurrently monitored group of 100 surgery patients who were not critically ill. The a priori computer-predicted dosage requirements of the critically ill patients were also compared with the dosages derived from their individualized pharmacokinetic values, and intrapatient variation in the critically ill patients was studied. ⋯ The a priori computer predictions for the critically ill patients were significantly lower than the individualized values for V, CL, dose, and amount of drug per 24 hours. The dosing regimen from the a priori model was the same as the individualized regimen in only 2/100 patients. In the 76 critically ill patients who had a second pharmacokinetic analysis performed, there was a significant decrease in k and CL from the first analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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Predictions of free (unbound) serum phenytoin concentration by three methods were compared with results obtained by the Abbott TDx Free Phenytoin ultrafiltration and fluorescence-polarization immunoassay technique. Data were obtained for hospitalized adults who had been receiving phenytoin for at least five days and were free of renal or hepatic disease. Total phenytoin concentration was determined, and free phenytoin concentration was measured in ultrafiltrate at 25 degrees C. ⋯ There was a strong correlation between actual and predicted free phenytoin concentrations for each of the methods, but all methods were found to lack precision. All methods also exhibited bias, as demonstrated by overprediction of the free concentration; however, none of the methods exhibited bias when the difference between the in vitro temperature of 25 degrees C and the in vivo temperature of 37 degrees C was considered. Because of their poor precision, the three methods evaluated in this study are not recommended for predicting free phenytoin concentration.
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The treatment of two common adverse effects of dapsone (methemoglobinemia and hemolytic anemia) is discussed, and a case of acute dapsone intoxication is described. A pregnant 29-year-old woman was admitted to an emergency room three hours after ingesting 50 tablets of dapsone (100 mg each) and six alcoholic drinks. One hour after admission 50 g of activated charcoal was given p.o., and 65 mg of methylene blue was given i.v. ⋯ Methemoglobin concentrations never rose above 20% after the sixth dose of methylene blue. On hospital days 2 and 3, laboratory values were consistent with a diagnosis of hemolytic anemia; the patient received two units of packed red blood cells. The hematocrit decreased over the next three days to 23.9%, and the patient received four units of packed red blood cells.(ABSTRACT TRUNCATED AT 250 WORDS)