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Biomedical subjects

Keith M Olsen

Publications and source records attributed to Keith M Olsen.

7 recordsLinked to original sources
PubMed2003

Efficacy of liposome-encapsulated ciprofloxacin compared with ciprofloxacin and ceftriaxone in a rat model of pneumococcal pneumonia.

Encapsulation of ciprofloxacin in sterically stabilized liposomes results in a prolonged circulation time and improved pharmacokinetics. Liposome-encapsulated ciprofloxacin was compared with conventional ciprofloxacin and ceftriaxone in a rat model of pneumococcal pneumonia. Male Sprague-Dawley rats were infected transtracheally with type 3 Streptococcus pneumoniae and then treated with intravenous ceftriaxone (100 mg/kg), ciprofloxacin (40 or 80 mg/kg) or liposomal ciprofloxacin (40 or 80 mg/kg) administered once or twice daily for 3 days. White blood counts, development of bacteraemia and mortality were measured for 10 days. Antibiotic concentrations in serum, lung lavage fluid and white blood cells recovered from lung lavage fluid were determined. Liposomal ciprofloxacin concentrations were significantly higher in serum and lavage fluid compared with conventional ciprofloxacin, resulting in greater area under the serum concentration-time curve and maximum serum concentration. Despite these higher concentrations, survival rates were similar between groups treated with equivalent doses of liposomal ciprofloxacin versus ciprofloxacin. When antibiotics were given once daily, ceftriaxone was more effective than either form of ciprofloxacin.

Animals↗
PubMed2002

The treatment of experimental osteomyelitis by surgical debridement and the implantation of calcium sulfate tobramycin pellets.

Calcium sulfate was used as a biodegradable delivery system for the administration of antibiotics in musculoskeletal infection. New Zealand white rabbits were infected with Staplylococcus aureus, debrided, and randomized to one of four treatment groups: calcium sulfate pellets with 10% tobramycin sulfate, placebo calcium sulfate pellets and IM tobramycin, placebo calcium sulfate pellets, or debridement. Serum and wound exudate tobramycin concentrations and serum calcium levels were measured. Radiographs, cultures, and histology were analyzed for efficacy and treatment. Rabbits treated with 10% tobramycin sulfate pellets showed a significantly higher eradication of infection (11/13) than rabbits treated with debridement only (5/12), placebo pellets and IM tobramycin (5/14). or placebo pellets (3/13). In the group receiving 10% tobramycin sulfate pellets, serum tobramycin concentrations peaked 3 h post-operatively at 5.87 microg/ml and were non-detectable after day 1. In the group receiving placebo pellets and IM tobramycin, serum concentrations peaked at 7.82 microg/ml 1 h post-operatively, fell to 6.12 microg/ml on day 2, and averaged 4.18 microg/ ml for the remainder of the treatment period. The wound exudate tobramycin concentrations in the animals treated with tobramycin sulfate pellets peaked at 11.9 mg/ml on day 1 and dropped to 2.5 microg/ml on day 7. There was no significant difference in the serum calcium levels in any of the treatment groups. Calcium sulfate containing tobramycin sulfate has potential utility as a biodegradable local antibiotic delivery system in the treatment of musculoskeletal infections.

Animals↗
PubMed2002

The effect of sampling method on the elution of tobramycin from calcium sulfate.

Release rate is a critical property of all drug delivery vehicles, including antibiotic-laden bioerodibles. In vitro elution studies, used to evaluate release rates, use different sampling methods, including changing the entire amount of buffer and partial exchanges each day. Two groups of 10% calcium sulfate-tobramycin pellets were eluted in 20 mL of buffer for 30 days. Group I had 5 mL of buffer withdrawn and replaced daily whereas Group II had the entire 20 mL of buffer changed daily. The results show that the complete exchange method caused a significantly faster release of antibiotic than the partial exchange method. In the complete exchange group, greater than 50% of the tobramycin was released by 24 hours, whereas in the partial exchange group, 50% of the antibiotic was not released until Day 6. The two methods of sampling used to evaluate this bioerodible material provide data that allow the user to anticipate how the material will function in relatively inert and volatile environments. The method used to sample the elution of antibiotics from bioerodible materials affects the amount of antibiotic eluted. It therefore is important to know the method of sampling when making a decision to use a bioerodible material to deliver antibiotics locally.

Anti-Bacterial Agents↗
PubMed2002

Omeprozole therapy in pediatric patients after liver and intestinal transplantation.

BACKGROUND: Proton pump inhibitors such as omeprazole are increasingly used to prevent stress-related gastric bleeding in critically ill patients. In this investigation, the acid-suppressive potency of omeprazole was assessed in one at-risk group, pediatric patients undergoing liver or intestinal transplantation, or both. METHODS: Twenty-two patients ranging in age from 0.9 to 108 months (23.8 +/- 6.5) underwent isolated liver (n = 10) or intestinal (11 with composite liver allografts) transplantation. Omeprazole was delivered in bicarbonate suspension through a nasogastric tube. Therapy was started after surgery at 0.5 mg/kg every 12 hours. Gastric pH monitoring was performed approximately 2 days later. RESULTS: For the entire group, mean gastric pH equaled 6.1 +/- 0.3, the same in recipients of isolated liver and intestinal allografts. Twelve of the 22 patients demonstrated a discontinuous omeprazole effect, that is, dissipation of acid reduction before the next dose. Five of the 12 patients with discontinuous omeprazole effect had mean gastric pH of less than 5 (3.9 +/- 0.4). In 4 of these 5, the omeprazole dosing interval was shortened to every 8 or every 6 hours, resulting in an increase in mean pH to 6.6 +/- 0.2 ( P < 0.01). In the remaining 10 of 22 patients, acid suppression was uninterrupted until the next dose. No patient experienced bleeding attributable to gastric erosion. CONCLUSION: Omeprazole suspended in sodium bicarbonate is an effective acid-suppressing agent in pediatric recipients of liver or intestinal transplant, or both. A dosage of 0.5 mg/kg every 12 hours is sufficient for most patients, but dosing every 6 to 8 hours is required to assure maximal acid suppression in all.

Anti-Ulcer Agents↗
PubMed2002

Pharmacodynamic activity and efficacy of linezolid in a rat model of pneumococcal pneumonia.

Linezolid is a new oxazolidinone antibiotic with potent activity against gram-positive bacteria, including Streptococcus pneumoniae. The pharmacodynamic activity and in vivo efficacy of linezolid were compared to those of ceftriaxone in an immunocompetent rat model of pneumococcal pneumonia. Rats infected intratracheally with 8 x 10(7) CFU of a penicillin-sensitive (MIC, 0.032 microg/ml) strain of S. pneumoniae were treated for 5 days beginning 18 h postinfection. Groups of rats were sham treated with oral phosphate-buffered saline or received oral liquid linezolid at 25 or 50 mg/kg of body weight twice a day (b.i.d.) or subcutaneous ceftriaxone at 100 mg/kg once daily. Mortality was monitored for 10 days postinfection; blood culturing was performed on day 1 (pretreatment) and on days 3, 5, and 10 postinfection for the determination of bacteremia. Serum also was collected for the determination of pharmacokinetic and pharmacodynamic parameters at 30 min and at 3, 5, and 12 h (linezolid) or 3, 5, and 24 h (ceftriaxone) postdose. The cumulative mortality rates were 100% for the sham-treated group, 58.3% for the low-dose linezolid group, 8.3% for the high-dose linezolid group, and 0% for the ceftriaxone group. Rats in each of the antibiotic treatment groups had significantly fewer bacteria (P < 0.00001) in their bronchoalveolar lavage fluid (BALF) on day 3 postinfection than sham-treated rats. There also were significantly fewer organisms in the BALF of rats treated with ceftriaxone than in the BALF of rats treated with either dose of linezolid. Oral linezolid at 50 mg/kg b.i.d. therefore was as effective as ceftriaxone in experimental pneumococcal pneumonia, whereas the 25-mg/kg b.i.d. dose was significantly less effective. All pharmacodynamic parameters reflected efficacy and were significantly different for the two dosage regimens of linezolid (P < 0.01). However, the free-fraction pharmacodynamic parameters predictive of outcome were a value of >39% for the percentage of time in the experimental dosing interval during which the linezolid concentration exceeded the MIC and a value of >147 for the ratio of the area under the serum concentration-time curve to the MIC.

Acetamides↗
PubMed2002

Pharmacokinetics and clinical use of drotrecogin alfa (activated) in patients with severe sepsis.

Drotrecogin alfa (activated) pharmacokinetics have been reported in healthy volunteers and in patients with severe sepsis. Clearance is rapid and appears to increase with weight; consequently, drotrecogin alfa (activated) is dosed on a weight basis. Drotrecogin alfa (activated) promotes fibrinolysis and inhibits thrombin production to produce an anticoagulant effect. The primary adverse events are related to its pharmacologic activity, with serious bleeding reported in 3.5% of patients receiving the drug in a multicenter phase III trial compared with 2.0% for patients receiving placebo. Monitoring parameters correspond with bleeding and should include international normalized ratio, platelet count, hematocrit, and overt signs of bleeding. Because of the protein nature of drotrecogin alfa (activated), pharmacists should be aware of the proper preparation and stability issues in order to afford efficient, cost-effective administration. As further data on drotrecogin alfa (activated) therapy become available, dosing and monitoring strategies may be altered to optimize the clinical benefits.

Anti-Infective Agents↗