Biomedical subjects

W E Fitzsimmons

Publications and source records attributed to W E Fitzsimmons.

40 records · Page 3Linked to original sources

PubMedDate not supplied

Single dose comparison of the relative bioavailability of phenytoin suspension and extended capsules.

There is presently only one preparation of phenytoin approved for once-daily dosing--extended phenytoin sodium capsules. We have observed many hospitalized patients switched from either this preparation or the intravenous form of phenytoin to phenytoin oral suspension. The bioavailability and single dose pharmacokinetics of extended phenytoin sodium capsules (Dilantin Kapseals) and phenytoin oral suspension (Dilantin oral suspension) were compared in seven healthy adult volunteers. Each subject was administered both three 100-mg Dilantin Kapseals (276 mg free acid) and 11 ml (275 mg) Dilantin-125 oral suspension in a randomized cross-over design with a 1-week washout period between preparations. Blood samples were drawn over 78 h after the administration of each preparation for determination of serum phenytoin concentration. In addition, total urinary output was collected for 48 h. Statistical analysis consisted of a comparison of the area under the curve (AUC) from time zero to 48 h and time-to-peak concentration using a two-tailed paired t test at a level of significance of p less than 0.05. The total alpha level was 0.10. No significant differences were found between the two preparations. The power of detecting a 15% difference in AUC was 0.80, and the power of detecting a 5-h difference in time to peak was 0.52. Following is a summarization of the pharmacokinetic parameters (capsules mean +/- 1 SD; suspension mean +/- 1 SD).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Effect of two administration schedules of an enteral nutrient formula on phenytoin bioavailability.

Continuous nasogastric (NG) administration of enteral nutrient formulas (ENFs) reportedly lowers phenytoin (PHT) concentrations. We studied the effects of two administration schedules of an ENF on the bioavailability of PHT. Eight healthy volunteers received 400 mg PHT suspension after fasting (A), with hourly Ensure (B), and with 4-hourly Ensure (C) in a randomized, crossover design. Data obtained from 13 serum samples collected over 80 h were analyzed using ESTRIP. Area under the serum concentration-time curve (AUC), time to maximum serum concentration (Tmax), and urinary excretion of 5-(p-hydroxyphenyl) 5-phenylhydantoin (HPPH) were compared by analysis of variance (ANOVA) and Bonferroni t tests of differences between means. AUCs (mg x h/L) were not different (p greater than 0.05) for A (222.1 +/- 86.9), B (233.9 +/- 92.9), and C (226.0 +/- 95.7). Tmax (h) was significantly shorter (p less than 0.05) when PHT was administered with Ensure (B = 8.5 +/- 3.0, C = 5.3 +/- 2.0) than without Ensure (A = 18.5 +/- 10.5). The HPPH excretion (mg/80 h) was not different (p greater than 0.05) for A (225.6 +/- 48.5), B (238.6 +/- 26.6), and C (229.9 +/- 45.6). Clearance and maximum concentration correlated with AUC, obviating the need for analysis. Relative bioavailability was B/A = 1.07 +/- 0.21, C/A = 1.01 +/- 0.14. The bioavailability of PHT was not decreased by either ENF administration schedule. Factors other than direct contact may be responsible for the observed decreases in PHT concentrations by coadministered ENFs.

Administration, Oral↗

PubMedDate not supplied

Influence of assay methodologies and interferences on the interpretation of digoxin concentrations.

The interpretation of serum digoxin concentrations is an area where pharmacists can have substantial clinical input. Important in this interpretation is the knowledge of various factors that may interfere with the reported concentration. These include drugs, metabolites of digoxin, protein concentration, and endogenous digoxin-like substances. The patients for whom these interferences are most significant include neonates, patients with renal failure and liver disease, and pregnant women. Pharmacist knowledge of these interferences can have an important impact on the quality of patient care.

Blood Proteins↗

PubMedDate not supplied

Survey of vancomycin monitoring guidelines in Illinois hospitals.

Disparity exists in published recommendations for monitoring of vancomycin serum concentrations. To evaluate the degree of disparity of practice in Illinois, directors of pathology of 202 Illinois hospitals were surveyed to assess their vancomycin monitoring practices. Of the 202 surveys mailed, 82 were returned for a response rate of 41 percent. Most hospitals have 200-500 beds (60 percent) and are nonteaching institutions (72 percent). Two thirds of the hospitals sent vancomycin to an outside laboratory for analysis. Timing of postinfusion (peak) concentrations ranged from 0 minutes following end of infusion to 360 minutes. Approximately one half of the institutions reported a peak therapeutic range of 30-40 mg/L at 30 minutes following end of infusion. A great majority of institutions were consistent in recommended trough range, with 48 of 55 reporting 5-10 mg/L. Although there is some consistency among at least half of the hospitals, there is a great deal of variability among the other half in peak monitoring guidelines.

Data Collection↗