1,1'-Methylenebis[4-[(hydroxyimino)methyl]-pyridinium] (MMB4) dimethanesulfonate (DMS) is a bisquaternary pyridinium aldoxime that reactivates acetylcholinesterase inhibited by organophosphorus nerve agent. Time courses of MMB4 concentrations in plasma were characterized following 7-day repeated intramuscular (IM) administrations of MMB4 DMS to male and female Sprague-Dawley rats, New Zealand White rabbits, beagle dogs (single dose only), and rhesus monkeys at drug dose levels used in earlier toxicology studies. In general, there were no significant differences in MMB4 toxicokinetic (TK) parameters between males and females for all the species tested in these studies. After a single IM administration to rats, rabbits, dogs, and monkeys, MMB4 DMS was rapidly absorbed, resulting in average T max values ranging from 5 to 30 minutes. Although C max values did not increase dose proportionally, the overall exposure to MMB4 in these preclinical species, as indicated by area under the curve (AUC) extrapolated to the infinity (AUC∞) values, increased in an approximately dose-proportional manner. The MMB4 DMS was extensively absorbed into the systemic circulation after IM administration as demonstrated by greater than 80% absolute bioavailability values for rats, rabbits, and dogs. Repeated administrations of MMB4 DMS for 7 days did not overtly alter TK parameters for MMB4 in rats, rabbits, and monkeys (150 and 300 mg/kg/d dose groups only). However, C max and AUC values decreased in monkeys given 450 and 600 mg/kg IM doses of MMB4 DMS following repeated administrations for 7 days. Based on the TK results obtained from the current study and published investigations, it was found that the apparent volume of distribution and clearance values were similar among various preclinical species, except for the rat.
ST-20 (sodium 2,2-dimethylbutyrate) is a potential therapeutic agent for treatment of b-thalassemia and sickle cell disease. A subchronic oral toxicity study was conducted in Sprague-Dawley rats (10/sex/dose) at gavage dosages of 0 (vehicle control), 200, 600, or 1,000 mg/kg, once daily for up to 15 days followed by a 14-day recovery. Ataxia (females), rough coat/thin appearance (males), and decreased body weights were observed at 1,000 mg/kg. Functional observational battery (FOB) deficits were observed more frequently in females and included decreased body tone, rectal temperature, emotional reactivity, neuromotor-neuromuscular activity (as exhibited by a deficit in visual/tactile placing accuracy, ataxia, hind limb dragging, and decreased grip strength), and rearing. ST-20 caused a decrease in WBC/RBC counts and RBC parameters; increase in reticulocytes and red cell inclusion bodies; decrease in total protein, globulin, and glucose; and increase in AG ratio. Micronucleated polychromatic erythrocytes of the bone marrow increased significantly in males at 1,000 mg/kg. Mean liver and kidney weights increased, and hepatocellular hypertrophy was observed in males at 1,000 mg/kg. Toxicologic findings were fully recovered during the 14-day recovery period. In conclusion, the no-observed adverse effect level for FOB and general toxicity was 200 mg/kg following gavage administration of ST-20 for up to 15 consecutive days.
The Food and Drug Administration Animal Rule requires evaluation of cardiovascular and central nervous system (CNS) effects of new therapeutics. To characterize an adult and juvenile mouse model, neurobehavioral and cardiovascular effects and pathology of a single sublethal but toxic, 8 mg/kg, oral dose of potassium cyanide (KCN) for up to 41 days postdosing were investigated. This study describes the short- and long-term sensory, motor, cognitive, and behavioral changes associated with oral dosing of a sublethal but toxic dose of KCN utilizing functional observation battery and Tier II CNS testing in adult and juvenile mice of both sexes. Selected tissues (histopathology) were evaluated for changes associated with KCN exposure with special attention to brain regions. Telemetry (adult mice only) was used to evaluate cardiovascular and temperature changes. Neurobehavioral capacity, sensorimotor responsivity or spontaneous locomotor activity, and rectal temperature were significantly reduced in adult and juvenile mice at 30 minutes post-8 mg/kg KCN dose. Immediate effects of cyanide included bradycardia, adverse electrocardiogram arrhythmic events, hypotension, and hypothermia with recovery by approximately 1 hour for blood pressure and heart rate effects and by 2 hours for body temperature. Lesions consistent with hypoxia, such as mild acute tubular necrosis in the kidneys corticomedullary junction, were the only histopathological findings and occurred at a very low incidence. The mouse KCN intoxication model indicates rapid and completely reversible effects in adult and juvenile mice following a single oral 8 mg/kg dose. Neurobehavioral and cardiovascular measurements can be used in this animal model as a trigger for treatment.
The purpose was to investigate whether the pharmacokinetics and pharmacodynamics of prednisolone in the non-human primate was an appropriate surrogate for man. After single intravenous doses of 0.03, 0.3, and 3 mg kg(-1), prednisolone demonstrated a dose-dependent clearance and volume of distribution. When corrected for concentration-dependent protein binding, the free clearance was linear at the tested dose levels. The protein binding-corrected volume of distribution was similar across doses. The serum half-life was estimated as being between 2 and 4 h. Prednisolone exhibits near complete inhibition of the cytokines TNF-alpha, IL-1beta, IL-6 and IL-8 with very similar IC50 estimates from 0.09 to 0.16 microg ml(-1) (from 0.24 to 0.44 microM). The monkey demonstrated a similar pharmacokinetics-pharmacodynamics profile of prednisolone when compared with man (from the literature).
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