The effects of deferoxamine mesylate on iron elimination after blood transfusion in neonatal foals.

BACKGROUND: Hepatic failure is one of the more common complications in foals requiring blood transfusion to treat neonatal isoerythrolysis. Iron intoxication is likely the cause of hepatic injury. OBJECTIVES: To determine the effects of deferoxamine on iron elimination in normal foals. ANIMALS: Thirteen neonatal foals. METHODS: Randomized-controlled trial. At 1-3 days of age, foals received either 3 L of washed packed dam's red blood cells (RBC) or 3 L of saline IV once. Foals were treated with deferoxamine (1 g) or saline (5 mL) SC twice daily for 14 days. Foals were randomly assigned to 1 of 3 groups: RBC/deferoxamine (deferoxamine), RBC/saline (placebo), or saline/saline (control). Blood and urine samples and liver biopsy specimens were collected for measurement of hematological, biochemical, and iron metabolism variables. RESULTS: There was a significant (P<.05) increase in hematocrit, RBC count, and hemoglobin in the groups transfused with packed RBC as compared with controls at all times. Biochemical variables and liver biopsy scores were not significantly different between groups at any time. Urine iron concentrations and fractional excretion of iron were significantly higher in deferoxamine treated foals. By 14 days after transfusion, liver iron concentrations in foals treated with deferoxamine (79.9±30.9 ppm) were significantly lower than that of foals receiving placebo (145±53.0 ppm) and similar to that of controls (44.8±4.09 ppm). CONCLUSIONS AND CLINICAL IMPORTANCE: Deferoxamine enhances urinary iron elimination and decreases hepatic iron accumulation after blood transfusion in foals.

Disposition of oral telithromycin in foals and in vitro activity of the drug against macrolide-susceptible and macrolide-resistant Rhodococcus equi isolates.

The objectives of this study were to determine the serum and pulmonary disposition of telithromycin in foals and to determine the minimum inhibitory concentration (MIC) of telithromycin against macrolide-susceptible and macrolide-resistant Rhodococcus equi isolates. A single dose of telithromycin (15 mg/kg of body weight) was administered to six healthy 6-10-week-old foals by the intragastric route. Activity of telithromycin was measured in serum, pulmonary epithelial lining fluid (PELF), and bronchoalveolar lavage (BAL) cells using a microbiological assay. The broth macrodilution method was used to determine the MIC of telithromycin, azithromycin, clarithromycin and erythromycin against R. equi. Following intragastric administration, mean +/- SD time to peak serum telithromycin activity (T(max)) was 1.75 +/- 0.76 h, maximum serum activity (C(max)) was 1.43 +/- 0.37 microg/mL, and terminal half-life (t(1/2)) was 3.81 +/- 0.40 h. Telithromycin activity, 4 h postadministration was significantly higher in BAL cells (50.9 +/- 14.5 microg/mL) than in PELF (5.07 +/- 2.64 microg/mL), and plasma (0.84 +/- 0.25 microg/mL). The MIC(90) of telithromycin for macrolide-resistant R. equi isolates (8 microg/mL) was significantly higher than that of macrolide-susceptible isolates (0.25 microg/mL). The MIC of telithromycin for macrolide-resistant isolates (MIC(50)=4.0 microg/mL) was significantly lower than that of clarithromycin (MIC(50)=24.0 microg/mL), azithromycin (MIC(50)=256 microg/mL) and erythromycin (MIC(50)=24 microg/mL).

The effect of omeprazole paste on intragastric pH in clinically ill neonatal foals.

REASON FOR PERFORMING STUDY: Administration of omeprazole paste per os to healthy neonatal foals has been shown to effectively increase intragastric pH, but has not been evaluated in sick neonatal foals. OBJECTIVES: To determine the effect of orally administered omeprazole paste on intragastric pH in clinically ill neonatal foals requiring nasogastric intubation. METHODS: Intragastric pH was measured continuously for 24 h using an indwelling electrode and continuous data recording system in hospitalised neonatal foals age < or =2 days. Intragastric pH was measured for 12 h prior to (pretreatment period) and 12 h following (post treatment period) treatment with omeprazole paste (4 mg/kg bwt per os). All foals displayed periods of acidity (pH <4) prior to treatment. Statistical analysis compared pre- and post treatment mean and median intragastric pH, and percentage of time below pH 4. RESULTS: Eight foals were evaluated age 1-3 days, a gestational age of at least 320 days or reported to be full term. The mean (3.19 +/- 1.50 vs. 6.20 +/- 0.93) and median (4.6 +/- 1.7 vs. 6.86 +/- 0.89) pH were significantly higher and the percentage of time below pH 4 (32.25 vs. 1.1%) was significantly lower in the post treatment compared to the pretreatment period. CONCLUSION: Omeprazole paste effectively increases intragastric pH in clinically ill neonatal foals after one dose at 4 mg/kg bwt orally.

Effect of age, feeding, and omeprazole administration on gastric tonometry in healthy neonatal foals.

BACKGROUND: Gastric tonometry is commonly used in humans as an assessment of intestinal mucosal perfusion. Values in healthy foals are currently unknown. HYPOTHESIS: Age, enteral feeding, and omeprazole administration would significantly alter gastric tonometry measurements in neonatal foals. ANIMALS: Nine clinically normal foals were used to assess the effect of age and feeding, and 8 similar foals were used to assess the effect of omeprazole. METHODS: At 1, 7, and 14 days of age, gastric intramucosal PCO2 (PgCO2) and arterial blood gas samples were obtained at baseline, immediately after feeding milk, and 1 and 2 hours after fasting for calculation of the intramucosal-arterial PCO2 difference (DeltaCO2). To evaluate the effect of omeprazole, foals were evaluated twice as above, 2 hours after fasting, comparing administration of omeprazole to no drug. RESULTS: There was a significant effect of age and feeding on PgCO2 and DeltaCO2, whereas arterial PCO2 was not significantly affected by these factors. Postfeeding DeltaCO2 values were significantly lower than fasted values. Baseline and postfeeding DeltaCO2 increased with age. There was no significant effect of age on data collected after 1 or 2 hours of fasting. The 90% reference interval for DeltaCO2 data collected after fasting was 0-54 mmHg. Foals had a significantly higher mean gastric pH and significantly higher DeltaCO2 and PgCO2 following omeprazole relative to no treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: Because of the high and variable DeltaCO2, which is exacerbated by omeprazole administration, the reference interval in foals is extremely wide.