The infusion of a low dose of endotoxin into healthy subjects triggers a complex inflammatory res... more The infusion of a low dose of endotoxin into healthy subjects triggers a complex inflammatory response but the intricacies of which, despite extensive research, are still being unraveled. Nine healthy male volunteers received a dose of 30 Units endotoxin/kg bodyweight as an intravenous bolus. Following endotoxin infusion the concentration of TNF-alpha in their serum rapidly increased within 30 min, peaked after 1-2 h and returned to baseline by 4 h. This corresponded to a similarly rapid increase in anti-inflammatory soluble TNF receptor (sTNFR) levels, which remained elevated for up to 48 h. Increased levels of other cytokines were measured, including IL-6, IL-8, G-CSF, IL-1ra and IL-10. However, these cytokines lagged behind that of TNF-alpha and remained elevated for up to 8 h. Endotoxin injection resulted in complex changes in HLA-DR expression, a marker of monocyte activation state. Initially, following a lag of 2-4 h, HLA-DR expression decreased with a nadir at 8 h, followed by an increase in expression above baseline at 22 h. HLA-DR levels returned to baseline 48 h post-endotoxin challenge. This was in contrast to endotoxin-induced changes in white blood cell (WBC) numbers, which dropped rapidly (at 2-3 h) while HLA-DR levels were stable and then peaked during the nadir in HLA-DR expression (8 h). Furthermore, endotoxin injection caused activation of both fibrinolytic and coagulation pathways. Thus, endotoxin infusion results in complex changes in HLA-DR expression, production of pro- and anti-inflammatory cytokines and activation of coagulation.
A model was developed that is capable of simulating antibacterial agent concentration versus time... more A model was developed that is capable of simulating antibacterial agent concentration versus time profiles commonly observed following intravenous and intramuscular bolus injections, intravenous infusions, and oral doses, administered as single or multiple doses. The model consisted of two physical compartments separated by a membrane of a commercial hemodialyzer. The 1.08 m2 membrane surface area allowed rapid transmembrane passage of drugs and other small molecules, while membrane pore size prevented bacterial passage. These characteristics allowed bacteria in one of the two compartments of the model to be exposed to time-variant drug concentrations without affecting the number or concentration of bacteria. The model was used to study the effects of a multiple intravenous bolus dosage regimen of ampicillin on Escherichia coli ATCC 12407.
Theophylline interacts pharmacokinetically with a variety of other drugs. Recently enoxacin was f... more Theophylline interacts pharmacokinetically with a variety of other drugs. Recently enoxacin was found to change theophylline's disposition. In a four-subject, four-way crossover study enoxacin was administered every 12 hours at four levels (0, 25, 100, and 400 mg) for 14 doses. With the ninth dose of enoxacin, 200 mg theophylline was coadministered. Blood and urine samples were assayed by sensitive and specific assays for the parent drugs and their metabolites. Significant reduction in the formation of theophylline's three major metabolites occurred on coadministration of enoxacin. At the 400 mg dose level, enoxacin caused a threefold decrease in theophylline's plasma clearance, a fourfold decrease in the urinary recovery of 3-methylxanthine and 1,3-dimethylurate, and a threefold decrease in the recovery of 1-methylurate.
The effect of gastric acidity on the oral absorption of the quinolone antibiotic enoxacin was eva... more The effect of gastric acidity on the oral absorption of the quinolone antibiotic enoxacin was evaluated in 12 healthy volunteers. In a randomized, crossover design, single 400 mg oral enoxacin doses were administered on four occasions: alone, after 50 mg intravenous ranitidine, after 2 micrograms/kg subcutaneous pentagastrin, and after combined ranitidine and pentagastrin treatment. Gastric pH was monitored by radiotelemetry capsule for 4 hours after enoxacin administration. Ranitidine pretreatment reduced enoxacin oral bioavailability by an average of 26%. This effect was abolished when pentagastrin was used to maintain low gastric pH. Thus the ranitidine-induced decrease in enoxacin oral bioavailability probably results from a decrease in gastric acidity rather than from an interaction with ranitidine itself.
ABSTRACT A model was developed that is capable of simulating antibacterial agent concentration ve... more ABSTRACT A model was developed that is capable of simulating antibacterial agent concentration versus time profiles commonly observed following intravenous and intramuscular bolus injections, intravenous infusions, and oral doses, administered as single or multiple doses. The model consisted of two physical compartments separated by a membrane of a commercial hemodialyzer. The 1.08 m2 membrane surface area allowed rapid transmembrane passage of drugs and other small molecules, while membrane pore size prevented bacterial passage. These characteristics allowed bacteria in one of the two compartments of the model to be exposed to time-variant drug concentrations without affecting the number or concentration of bacteria. The model was used to study the effects of a multiple intravenous bolus dosage regimen of ampicillin on Escherichia coli ATCC 12407.
A newly developed high-pressure liquid chromatographic method was used to study the optimum dosag... more A newly developed high-pressure liquid chromatographic method was used to study the optimum dosage regimen needed to suppress endogenous hydrocortisone. Nine volunteers were randomly placed in three groups. Each group received 1 mg of dexamethasone at 11 pm (Treatment A), 2 mg of dexamethasone at 11 pm (Treatment B), or 1 mg at 11 pm and an additional 1 mg at 6 am the following day (Treatment C). Analysis of multiple blood samples obtained the day before and the day after drug administration showed suppression in all three groups. Although the duration and extent of this suppression varied, adequate suppression to permit bioavailability studies was observed for Treatments B and C.
The pharmacokinetics of hydrocortisone were examined following single doses of 5-, 10-, 20-, and ... more The pharmacokinetics of hydrocortisone were examined following single doses of 5-, 10-, 20-, and 40-mg hydrocortisone suspensions to healthy male volunteers. Endogenous hydrocortisone was suppressed by giving 2 mg of dexamethasone the night before hydrocortisone administration. Plasma samples obtained serially for 12 hr after hydrocortisone administration were assayed by reversed-phase high-pressure liquid chromatography using a fixed-wavelength (254 nm) UV absorbance detector. Drug absorption was rapid, with mean maximum plasma hydrocortisone concentrations occurring within 60 min of dosing. Subsequent drug elimination was monophasic with mean elimination half-lives increasing from 1.2 hr for the 5-mg dose to 1.7 hr for the 40-mg dose. Increase in AUC and Cmax with increasing dose were linear but not directly proportional to dose size. This was attributed to dose-dependent absorption or to loss of drug the first-pass through the liver.
The influence of coadministration on digoxin and azimilide pharmacokinetics/pharmacodynamics was ... more The influence of coadministration on digoxin and azimilide pharmacokinetics/pharmacodynamics was assessed in a randomized, 3-way crossover study in 18 healthy men. Serial blood and urine samples were obtained for azimilide and digoxin quantitation. Treatment effects on pharmacokinetics were assessed using analysis of variance. The relationship between azimilide blood concentrations and QT(c) prolongation was characterized by an E(max) model. Effects of coadministration on pharmacodynamics were assessed using a mechanistic-based inhibition model. Azimilide pharmacokinetics was unaffected by digoxin, except for a 36% increase in CL(r) (P = .0325), with no change in CL(o). Digoxin pharmacokinetics was unaffected by azimilide, except for a 21% increase in C(max) (P = .0176) and a 10% increase in AUC(tau) (P = .0121). Digoxin coadministration increased the apparent EC(50) with no effect on E(max), consistent with competitive inhibition (K(i) = 0.899 ng/mL). The pharmacokinetic and pharmacodynamic changes observed upon coadministration were small and are not expected to be clinically important.
The bioavailability of bevantolol was compared in 12 healthy volunteers given single doses of the... more The bioavailability of bevantolol was compared in 12 healthy volunteers given single doses of the drug as the HCl salt after an overnight fast, or 15 minutes before or after a standardized breakfast in a nonblind, randomized crossover design. Bevantolol was rapidly absorbed in all three treatment groups, with maximum concentrations (Cmax) observed at 1.0, 0.9, and 1.8 hours for the fasting, before breakfast, and after breakfast groups, respectively. Time to Cmax was significantly longer than fasting only when bevantolol was given after breakfast. Food ingestion did not significantly affect Cmax, total of absorbed drug, or the drug elimination rate. Since food only slightly decreases the drug absorption rate and has no measurable effect on the extent of drug absorption, the relationship of bevantolol administration to meals is not expected to influence therapeutic efficacy.
Enoxacin is a quinolone antibacterial agent currently being developed for oral and intravenous tr... more Enoxacin is a quinolone antibacterial agent currently being developed for oral and intravenous treatment of bacterial infections. Ten healthy subjects received a single 400-mg intravenous dose of enoxacin alone, with 300 mg (four times daily) oral cimetidine and with 150 mg (twice daily) oral ranitidine. Serial blood and urine samples were collected over a 48-hour period. Plasma and urine enoxacin concentrations were determined using a validated high-performance liquid chromatographic method. Mean enoxacin plasma concentrations were higher after administration of enoxacin with cimetidine than those measured after enoxacin alone or enoxacin with ranitidine. Cimetidine coadministration reduced enoxacin renal clearance by 26% and systemic clearance by 20%, and resulted in a 30% increase in elimination half-life. In contrast, concurrent ranitidine therapy did not significantly alter the pharmacokinetics of intravenous enoxacin.
The infusion of a low dose of endotoxin into healthy subjects triggers a complex inflammatory res... more The infusion of a low dose of endotoxin into healthy subjects triggers a complex inflammatory response but the intricacies of which, despite extensive research, are still being unraveled. Nine healthy male volunteers received a dose of 30 Units endotoxin/kg bodyweight as an intravenous bolus. Following endotoxin infusion the concentration of TNF-alpha in their serum rapidly increased within 30 min, peaked after 1-2 h and returned to baseline by 4 h. This corresponded to a similarly rapid increase in anti-inflammatory soluble TNF receptor (sTNFR) levels, which remained elevated for up to 48 h. Increased levels of other cytokines were measured, including IL-6, IL-8, G-CSF, IL-1ra and IL-10. However, these cytokines lagged behind that of TNF-alpha and remained elevated for up to 8 h. Endotoxin injection resulted in complex changes in HLA-DR expression, a marker of monocyte activation state. Initially, following a lag of 2-4 h, HLA-DR expression decreased with a nadir at 8 h, followed by an increase in expression above baseline at 22 h. HLA-DR levels returned to baseline 48 h post-endotoxin challenge. This was in contrast to endotoxin-induced changes in white blood cell (WBC) numbers, which dropped rapidly (at 2-3 h) while HLA-DR levels were stable and then peaked during the nadir in HLA-DR expression (8 h). Furthermore, endotoxin injection caused activation of both fibrinolytic and coagulation pathways. Thus, endotoxin infusion results in complex changes in HLA-DR expression, production of pro- and anti-inflammatory cytokines and activation of coagulation.
A model was developed that is capable of simulating antibacterial agent concentration versus time... more A model was developed that is capable of simulating antibacterial agent concentration versus time profiles commonly observed following intravenous and intramuscular bolus injections, intravenous infusions, and oral doses, administered as single or multiple doses. The model consisted of two physical compartments separated by a membrane of a commercial hemodialyzer. The 1.08 m2 membrane surface area allowed rapid transmembrane passage of drugs and other small molecules, while membrane pore size prevented bacterial passage. These characteristics allowed bacteria in one of the two compartments of the model to be exposed to time-variant drug concentrations without affecting the number or concentration of bacteria. The model was used to study the effects of a multiple intravenous bolus dosage regimen of ampicillin on Escherichia coli ATCC 12407.
Theophylline interacts pharmacokinetically with a variety of other drugs. Recently enoxacin was f... more Theophylline interacts pharmacokinetically with a variety of other drugs. Recently enoxacin was found to change theophylline's disposition. In a four-subject, four-way crossover study enoxacin was administered every 12 hours at four levels (0, 25, 100, and 400 mg) for 14 doses. With the ninth dose of enoxacin, 200 mg theophylline was coadministered. Blood and urine samples were assayed by sensitive and specific assays for the parent drugs and their metabolites. Significant reduction in the formation of theophylline's three major metabolites occurred on coadministration of enoxacin. At the 400 mg dose level, enoxacin caused a threefold decrease in theophylline's plasma clearance, a fourfold decrease in the urinary recovery of 3-methylxanthine and 1,3-dimethylurate, and a threefold decrease in the recovery of 1-methylurate.
The effect of gastric acidity on the oral absorption of the quinolone antibiotic enoxacin was eva... more The effect of gastric acidity on the oral absorption of the quinolone antibiotic enoxacin was evaluated in 12 healthy volunteers. In a randomized, crossover design, single 400 mg oral enoxacin doses were administered on four occasions: alone, after 50 mg intravenous ranitidine, after 2 micrograms/kg subcutaneous pentagastrin, and after combined ranitidine and pentagastrin treatment. Gastric pH was monitored by radiotelemetry capsule for 4 hours after enoxacin administration. Ranitidine pretreatment reduced enoxacin oral bioavailability by an average of 26%. This effect was abolished when pentagastrin was used to maintain low gastric pH. Thus the ranitidine-induced decrease in enoxacin oral bioavailability probably results from a decrease in gastric acidity rather than from an interaction with ranitidine itself.
ABSTRACT A model was developed that is capable of simulating antibacterial agent concentration ve... more ABSTRACT A model was developed that is capable of simulating antibacterial agent concentration versus time profiles commonly observed following intravenous and intramuscular bolus injections, intravenous infusions, and oral doses, administered as single or multiple doses. The model consisted of two physical compartments separated by a membrane of a commercial hemodialyzer. The 1.08 m2 membrane surface area allowed rapid transmembrane passage of drugs and other small molecules, while membrane pore size prevented bacterial passage. These characteristics allowed bacteria in one of the two compartments of the model to be exposed to time-variant drug concentrations without affecting the number or concentration of bacteria. The model was used to study the effects of a multiple intravenous bolus dosage regimen of ampicillin on Escherichia coli ATCC 12407.
A newly developed high-pressure liquid chromatographic method was used to study the optimum dosag... more A newly developed high-pressure liquid chromatographic method was used to study the optimum dosage regimen needed to suppress endogenous hydrocortisone. Nine volunteers were randomly placed in three groups. Each group received 1 mg of dexamethasone at 11 pm (Treatment A), 2 mg of dexamethasone at 11 pm (Treatment B), or 1 mg at 11 pm and an additional 1 mg at 6 am the following day (Treatment C). Analysis of multiple blood samples obtained the day before and the day after drug administration showed suppression in all three groups. Although the duration and extent of this suppression varied, adequate suppression to permit bioavailability studies was observed for Treatments B and C.
The pharmacokinetics of hydrocortisone were examined following single doses of 5-, 10-, 20-, and ... more The pharmacokinetics of hydrocortisone were examined following single doses of 5-, 10-, 20-, and 40-mg hydrocortisone suspensions to healthy male volunteers. Endogenous hydrocortisone was suppressed by giving 2 mg of dexamethasone the night before hydrocortisone administration. Plasma samples obtained serially for 12 hr after hydrocortisone administration were assayed by reversed-phase high-pressure liquid chromatography using a fixed-wavelength (254 nm) UV absorbance detector. Drug absorption was rapid, with mean maximum plasma hydrocortisone concentrations occurring within 60 min of dosing. Subsequent drug elimination was monophasic with mean elimination half-lives increasing from 1.2 hr for the 5-mg dose to 1.7 hr for the 40-mg dose. Increase in AUC and Cmax with increasing dose were linear but not directly proportional to dose size. This was attributed to dose-dependent absorption or to loss of drug the first-pass through the liver.
The influence of coadministration on digoxin and azimilide pharmacokinetics/pharmacodynamics was ... more The influence of coadministration on digoxin and azimilide pharmacokinetics/pharmacodynamics was assessed in a randomized, 3-way crossover study in 18 healthy men. Serial blood and urine samples were obtained for azimilide and digoxin quantitation. Treatment effects on pharmacokinetics were assessed using analysis of variance. The relationship between azimilide blood concentrations and QT(c) prolongation was characterized by an E(max) model. Effects of coadministration on pharmacodynamics were assessed using a mechanistic-based inhibition model. Azimilide pharmacokinetics was unaffected by digoxin, except for a 36% increase in CL(r) (P = .0325), with no change in CL(o). Digoxin pharmacokinetics was unaffected by azimilide, except for a 21% increase in C(max) (P = .0176) and a 10% increase in AUC(tau) (P = .0121). Digoxin coadministration increased the apparent EC(50) with no effect on E(max), consistent with competitive inhibition (K(i) = 0.899 ng/mL). The pharmacokinetic and pharmacodynamic changes observed upon coadministration were small and are not expected to be clinically important.
The bioavailability of bevantolol was compared in 12 healthy volunteers given single doses of the... more The bioavailability of bevantolol was compared in 12 healthy volunteers given single doses of the drug as the HCl salt after an overnight fast, or 15 minutes before or after a standardized breakfast in a nonblind, randomized crossover design. Bevantolol was rapidly absorbed in all three treatment groups, with maximum concentrations (Cmax) observed at 1.0, 0.9, and 1.8 hours for the fasting, before breakfast, and after breakfast groups, respectively. Time to Cmax was significantly longer than fasting only when bevantolol was given after breakfast. Food ingestion did not significantly affect Cmax, total of absorbed drug, or the drug elimination rate. Since food only slightly decreases the drug absorption rate and has no measurable effect on the extent of drug absorption, the relationship of bevantolol administration to meals is not expected to influence therapeutic efficacy.
Enoxacin is a quinolone antibacterial agent currently being developed for oral and intravenous tr... more Enoxacin is a quinolone antibacterial agent currently being developed for oral and intravenous treatment of bacterial infections. Ten healthy subjects received a single 400-mg intravenous dose of enoxacin alone, with 300 mg (four times daily) oral cimetidine and with 150 mg (twice daily) oral ranitidine. Serial blood and urine samples were collected over a 48-hour period. Plasma and urine enoxacin concentrations were determined using a validated high-performance liquid chromatographic method. Mean enoxacin plasma concentrations were higher after administration of enoxacin with cimetidine than those measured after enoxacin alone or enoxacin with ranitidine. Cimetidine coadministration reduced enoxacin renal clearance by 26% and systemic clearance by 20%, and resulted in a 30% increase in elimination half-life. In contrast, concurrent ranitidine therapy did not significantly alter the pharmacokinetics of intravenous enoxacin.
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