Differential enantioselectivity and product-dependent activation and inhibition in metabolism of verapamil by human CYP3As.

In vitro studies of enantioselective metabolism of R-(+)- and S-(-)verapamil (VER) were conducted using human cDNA-expressed CYP3A isoforms, CYP3A4, CYP3A5, and CYP3A7. N-dealkylated products nor-VER [2,8-bis-(3,4-dimethoxyphenyl)-2-isopropyl-6-azaoctanitrile] and D617 [2-(3,4-dimethoxyphenyl)-5-methylamino-2-isopropylvaleronitrile] were the major metabolites for all CYP3A isoforms regardless of enantiomer. Enantioselectivity of CYP3A4 and CYP3A7 was most similar among the three isoforms. This coincides with the degree of homology of amino acids at the active sites and in the total amino acid sequences of the enzymes. Biphasic substrate inhibition was observed for the formation of nor-VER and D617, whereas simple biphasic kinetics were observed for the formation of O-demethylated products for both enantiomers with CYP3A4. The biphasic substrate inhibition was observed only for nor-VER, and simple biphasic kinetics were observed for D617 and O-demethylated products for both enantiomers with CYP3A5. However, with CYP3A7, D617 and O-demethylated products showed typical Michaelis-Menten kinetics, and only nor-VER displayed substrate (monophasic) inhibition. When metabolic rates of VER were determined in the presence of three different effectors, midazolam, testosterone, and nifedipine, activation, inhibition, or activation and inhibition of VER metabolism was observed depending on the enantiomers, metabolites, effectors, and cytochrome P450 isoforms. Addition of anti-CYP3A4 antibody inhibited formation of all metabolites for both CYP3A4 and CYP3A5. The atypical phenomena (biphasic substrate inhibition, activation, and inhibition depending on product formation) of VER kinetics could be adequately explained by introducing the concept of steric interaction into a two binding-site model.     

Localized pseudomembranous colitis in the cecum and ascending colon mimicking acute appendicitis

A 61-year-old male was admitted to our hospital due to right lower abdominal pain and watery diarrhea for 3 d.Beginning 3 wk before he arrived in our hospital,he took 3 rd-generation cephalosporin(cefixime) for 2 wk due to chronic left ear otitis media.Colonoscopic examination revealed yellowish patches of ulcerations and swelling covered with thick serosanguineous exudate in the cecum and ascending colon.After 7 d of oral metronidazole treatment,his symptoms completely disappeared.We report a case of localized pseudomembranous colitis in the cecum and ascending colon mimicking acute appendicitis associated with cefixime.     

Systematic mapping of fragile X granules in the mouse brain reveals a potential role for presynaptic FMRP in sensorimotor functions

Loss of Fragile X mental retardation protein (FMRP) leads to Fragile X syndrome (FXS), the most common form of inherited intellectual disability and autism. Although the functions of FMRP and its homologs FXR1P and FXR2P are well studied in the somatodendritic domain, recent evidence suggests that this family of RNA binding proteins also plays a role in the axonal and presynaptic compartments. Fragile X granules (FXGs) are morphologically and genetically defined structures containing Fragile X proteins that are expressed axonally and presynaptically in a subset of circuits. To further understand the role of presynaptic Fragile X proteins in the brain, we systematically mapped the FXG distribution in the mouse central nervous system. This analysis revealed both the circuits and the neuronal types that express FXGs. FXGs are enriched in circuits that mediate sensory processing and motor planning—functions that are particularly perturbed in FXS patients. Analysis of FXG expression in the hippocampus suggests that CA3 pyramidal neurons use presynaptic Fragile X proteins to modulate recurrent but not feedforward processing. Neuron‐specific FMRP mutants revealed a requirement for neuronal FMRP in the regulation of FXGs. Finally, conditional FMRP ablation demonstrated that FXGs are expressed in axons of thalamic relay nuclei that innervate cortex, but not in axons of thalamic reticular nuclei, striatal nuclei, or cortical neurons that innervate thalamus. Together, these findings support the proposal that dysregulation of axonal and presynaptic Fragile X proteins contribute to the neurological symptoms of FXS. J. Comp. Neurol. 520:3687–3706, 2012. © 2012 Wiley Periodicals, Inc.     

Reduced Systemic Availability of an Antiarrhythmic Drug,Bidisomide, with Meal Co-administration: Relationship with Region-Dependent Intestinal Absorption

Purpose. The aim of this research was to determine the mechanism by which a co-administered meal decreases the oral absorption of bidisomide and does not influence the oral absorption of the chemically-related antiarrhythmic agent, disopyramide. Methods. Bidisomide plasma levels, following oral administration and intravenous infusion in the fasted state and with various meal treatments, were determined in human subjects. A dialysis technique was employed to examine the potential for drug binding to meal homogenates. Plasma levels, following drug administration through duodenal and jejunal intestinal access ports and following various meal treatments with oral drug co-administration, were compared for bidisomide and disopyramide in a canine model. Results. Bidisomide plasma AUC was significantly reduced following oral drug co-administration with breakfast compared to fasted-state controls in human subjects and in dogs independent of the composition of the solid cooked breakfast. While intravenous bidisomide infusion in human subjects showed a statistically significant reduction in AUC 15 minutes after oral administration of a high fat breakfast as compared to drug infusion in the fasted state, the reduction (–13%) was substantially smaller than the reduction (from –43% to –63%) observed with oral bidisomide meal co-administration. The percentages of bidisomide and disopyramide lost by binding to homogenates of cooked breakfast were 25.0 ± 5.7% and 23.7 ± 7.7%, respectively, as determined by dialysis at 4 hours. In dogs, the extent of absorption of disopyramide was comparable from oral, duodenal and mid-jejunal administration while the extent of bidisomide absorption from mid-jejunal administration was significantly lower than for oral or duodenal administration. Non-viscous liquid meals decreased C_max but not AUC, while viscous homogenized solid meals decreased both C_max and AUC for bidisomide with oral drug-meal co-administration. Oral non-caloric hydroxypropyl methylcellulose meals decreased bidisomide to the same extent as homogenized solid meals but did not lower disopyramide AUC. Conclusions. The significant reduction in bidisomide plasma levels observed with meal co-administration in human subjects was predominantly mediated through a reduction in drug absorption and was independent of solid meal composition. The difference in meal effect on the absorption of the two drugs in humans did not appear to be a function of drug binding to cooked meal components over typical human upper gastrointestinal residence times. In dogs, the high-viscosity medium generated by oral co-administration of a solid meal reduced the upper intestinal absorption of bidisomide and disopyramide. Bidisomide AUC was decreased since it was well absorbed in the upper but not lower small intestine. Disopyramide AUC was not significantly affected since it was well absorbed from both regions. A similar mechanism may play a role in drug plasma level reductions following oral co-administration with solid meals for drugs showing similar regionally-dependent absorption profiles.     

Mechanism of Compound- and Species-Specific Food Effects of Structurally Related Antiarrhythmic Drugs,Disopyramide and Bidisomide

Purpose. To determine mechanism of food effects observed with bidisomide but not with the structurally similar drug, disopyramide. Methods. Food effect studies of bidisomide and disopyramide were conducted with and without a standardized high fat meal in healthy subjects and in the dog. Intestinal metabolism of disopyramide and absorption of the metabolites were examined after oral administration of the drug to the dogs with portal vein canula implanted. Effects of food or a mixture of amino acids on metabolism of [¹⁴C]disopyramide were examined after intraportal infusion of the drug with and without high fat meal and after drug infusion into portal vein with the amino acid mixture, respectively. Results. The systemic availability of bidisomide was markedly reduced with food in humans, whereas the systemic availability of disopyramide did not change notably. In the dog, the systemic availability of bidisomide was also reduced with food. The systemic availability of disopyramide did not change with food. This was due to the fact that reduction in absorption was compensated by reduction of metabolism. There was no evidence for reduction in hepatic and intestinal metabolism with food. Conclusions. The apparent reduction in disopyramide metabolism with food may be due to an increase in colonal and /or lymphatic absorption. Food effects on the apparent systemic availability of bidisomide and disopyramide in the dog were similar to those in the rat. However, there was substantial species difference in the mechanism of food effects.     

Head injuries in children under 36 months of age. Demography and outcome

Head injuries in children under the age of 3 years have not been extensively studied, due in part to the lack of an objective tool for neurological assessment. We have developed a Children's Coma Scale (CCS) by modifying the verbal response subscore of the Glasgow Coma Scale (GCS) to overcome this limitation. When applied prospectively to children under 3 years of age, we found the CCS to be useful in predicting outcome. During the 5-year study period from 1981 to 1985, there were 738 patients with head injuries (0-16 years) admitted to the Children's Memorial Hospital in Chicago, including 318 (43.1%) less than 3 years of age. Initial data demonstrated the following observations. The most common mechanism of injury was a fall (75.5%). Although a brief loss of consciousness (LOC) was reported in three-fourths of the patients, prolonged LOC of more than 6 h was uncommon (16/318, 5.0%). The classically described "lucid interval" was seen in only 7 children (2.2%) and was not a reliable indicator of epidural hematoma. Post-traumatic seizures developed more commonly in children under 2 years of age (15.7%) than in older children (11.6% under 3 years of age, 9.6%, entire group), (P less than 0.001). Oculovestibular reflex and bilateral fixed dilated pupils had the most reliable correlation with outcome. Other brain-stem reflexes were less useful.(ABSTRACT TRUNCATED AT 250 WORDS)     

Itraconazole IV nanosuspension enhances efficacy through altered pharmacokinetics in the rat

The goal of this research was to evaluate an intravenous itraconazole nanosuspension dosage form, relative to a solution formulation, in the rat. Itraconazole was formulated as a nanosuspension by a tandem process of microcrystallization followed by homogenization. Acute toxicity, pharmacokinetics, and distribution were studied in the rat, and compared with a solution formulation of itraconazole. Efficacy was studied in an immunocompromised rat model, challenged with a lethal dose of either itraconazole-sensitive or itraconazole-resistant C. albicans. Itraconazole nanosuspension was tolerated at significantly higher doses compared with a solution formulation. Pharmacokinetics of the nanosuspension were altered relative to the solution formulation. C(max) was reduced and t(1/2) was much prolonged. This occurred due to distribution of the nanosuspension to organs of the monocyte phagocytic system (MPS), followed by sustained release from this IV depot. The higher dosing of the drug, enabled in the case of the nanosuspension, led to higher kidney drug levels and reduced colony counts. Survival was also shown to be superior relative to the solution formulation. Thus, formulation of itraconazole as a nanosuspension enhances efficacy of this antifungal agent relative to a solution formulation, because of altered pharmacokinetics, leading to increased tolerability, permitting higher dosing and resultant tissue drug levels.     

Absorption and Disposition of a Selective Aldosterone Receptor Antagonist,Eplerenone, in the Dog

Purpose. The present study was conducted to characterize the pharmacokinetics of eplerenone (EP), a selective aldosterone receptor antagonist, and its open lactone ring form in the dog. Methods. Pharmacokinetic studies of EP were conducted in dogs following i.v., oral, and rectal dosing (15 mg/kg) and following intragastric, intraduodenal, intrajejunal, and intracolonic dosing (7.5 mg/kg). Results. After oral administration, the systemic availability of EP was 79.2%. Systemic availabilities following administration via other routes were similar to that following oral administration. The half-life and plasma clearance of EP were 2.21 hr and 0.329 l/kg/hr, respectively. Plasma concentrations of the open lactone ring form were lower than EP concentrations regardless of the route of administration. The C-14 AUC in red blood cells was approximately 64% and 68% of the plasma AUC for i.v. and oral doses. Percentages of the dose excreted as total radioactivity in urine and feces were 54.2% and 40.6%, respectively, after i.v. administration, and 40.7% and 52.3%, respectively, after oral administration. The percentages of the dose excreted in urine and feces as EP were 13.7% and 2.5%, respectively, after i.v. administration, and 2.1% and 4.6% after oral administration, respectively. Approximately 11% and 15% of the doses were excreted as the open form following i.v. and oral doses. Conclusions. EP was rapidly and efficiently absorbed throughout the gastrointestinal tract, resulting in a good systemic availability. The drug did not preferentially accumulate in red blood cells. EP was extensively metabolized; however, first-pass metabolism after oral and rectal administration was minimal. EP and its metabolites appear to be highly excreted in the bile.     

Effect of SC-40230, a new class I antiarrhythmic agent,on canine ventricular tachycardias

SC-40230, α-[2-[acetyl(1-methylethyl)amino]ethyl]-α-(2-chlorophenyl)-1-piperidinebutanamide, a new class I antiarrhythmic agent, was tested for efficacy against coronary ligation-induced arrhythmias and ouabain toxicity arrhythmias in dogs. Doses of 9mg/kg i.v. and 15, 25, and 35 mg/kg p.o. significantly reduced ectopic rate in conscious dogs that had undergone ligation of the left anterior descending coronary artery 24 hr prior to testing. Plasma concentrations of SC-40230 ranging from 3 to 9 μg/ml corresponded with ectopic rate reductions of 10–82% in the coronary ligation model. SC-40230 was well tolerated at all doses tested in the conscious dogs. A 5 mg/kg i.v. dose of SC-40230 converted ouabain-induced ventricular tachycardias to normal sinus rhythm in anesthetized dogs. The antiarrhythmic effect of SC-40230 in the ouabain toxicity model was reversed by large (? 240 U) doses of insulin. The experiments described in this study demonstrated that SC-40230 is a well-tolerated new class I antiarrhythmic agent with intravenous and oral effectiveness against ventricular arrhythmias.     

Species Dependent Esterase Activities for Hydrolysis of an Anti-HIV Prodrug Glycovir and Bioavailability of Active SC-48334

Purpose. The in vitro fate of an ester prodrug, glycovir, was studied to determine if the species differences in the bioavailability of pharmacologically active SC-48334 observed after glycovir administration and not observed after SC-48334 administration is due to species differences in ester hydrolysis rate or species differences in absorption of the prodrug itself, and to determine the site(s) of ester hydrolysis which contributes most to species differences in the bioavailability of SC-48334 if any. Methods. Glycovir was incubated with small intestinal mucosa, liver S9 fractions, whole blood, red blood cells (RBC) and plasma of the rat, dog, monkey (cynomolgus and rhesus) and man, and glycovir concentrations were determined by HPLC. Results. The relative bioavailabilities of SC-48334 after prodrug administration to the rat, dog, monkey and man were 99,15, 42 and 37%, respectively. After SC-48334 administration, SC-48334 was rapidly and similarly well absorbed in all species. The hydrolysis rate in the small intestinal mucosa was well correlated with the relative bioavailability of SC-48334 after prodrug administration. Among different species the hydrolysis rate of glycovir in liver S9 fractions, blood, RBC and plasma did not parallel those in the mucosa of the small intestine. Conclusions. The species differences in bioavailability of SC-48334 with the prodrug were due to species differences in hydrolysis rates of the prodrug in small intestinal mucosa. The monkey was a good animal model for prediction of esterase activity in human small intestine and relative bioavailability in man.