Altered Pharmacological Efficacy of Phenobarbital with the Treatment of 7,8-Dihydroxyflavone, an Agonist of Tropomyosin Receptor Kinase B, in Rats.

From our previous observation that the anesthetic effects of phenobarbital potentiate in rats with a decreased cerebral protein expression of the potassium chloride cotransporter KCC2 (SLC12A5), an in vivo study was conducted to clarify whether the pharmacological effect of phenobarbital alters by stimulating the cerebral tropomyosin receptor kinase B (TrkB) that is known to down-regulate the KCC2 protein expression. The stimulation was performed in rats with repetitious intraperitoneal administration of a TrkB agonist, namely 7,8-dihydroxyflavone (DHF). After that, the rats underwent an intraventricular infusion of phenobarbital using a dwelled cannula, and the onset time of the phenobarbital-induced general anesthesia was determined. In addition, their brain tissues were excised and cerebral cortices were collected. Then, subcellular fractions were prepared and the cerebral expression of various proteins involving the anesthetic effects of phenobarbital was examined. It was demonstrated that phenobarbital induced general anesthesia about 2 times faster in rats receiving the DHF treatment than in control rats, and that the phenobarbital amount in the brain tissue at the onset time of anesthesia was lower in rats with the treatment. Western blotting showed that the cerebral protein expression of KCC2 decreases, and the phosphorylation of the TrkB protein increases with the DHF treatment. These observations indicate that the anesthetic effects of phenobarbital potentiate with the TrkB stimulation and the resultant decrease in the cerebral KCC2 protein expression. The results also suggest that the TrkB protein and its phosphorylation status may be a key modulator of the pharmacological efficacy of phenobarbital.

Acute Peripheral Inflammation Increases Plasma Concentration of Hypoglycemic Agent Nateglinide with Decreased Hepatic Drug-Metabolizing Activity in Rats.

The effects of inflammation on hypoglycemic agents were evaluated in male rats with acute peripheral inflammation (API). Nateglinide (NTG) was utilized as a model compound, since it is a hepatically-metabolized compound and its metabolism is mainly mediated by CYP 2C11 enzyme. In the experiments, rats were subjected to carrageenan injection into their hind paws for API induction, and the plasma concentration profiles of NTG were then examined. In addition, pooled liver microsomes were prepared from control and API rats, and the hepatic drug-metabolizing activity toward NTG and the hepatic expression of CYP2C11 protein were evaluated. It was shown that the plasma concentration of NTG following its intravenous administration decreases at a slower rate in API rats than that in control rats. It was also indicated in the incubation study with the liver microsomes that the hepatic drug-metabolizing activity toward NTG decreases in API rats. Additionally, it was revealed in Western immunoblotting that the hepatic expression of CYP2C11 protein decreases in API rats. These findings suggest that inflammation occurring in peripheral tissues brings about a decrease in hepatic NTG metabolism by suppressing the hepatic expression of CYP2C11 protein, causing an alteration of the plasma concentration profile of NTG with its impaired elimination.

Effects of dexamethasone to reverse decreased hepatic midazolam metabolism in rats with acute renal failure.

The inductive effects of dexamethasone on hepatic midazolam metabolism were examined in Wistar rats with acute renal failure (ARF) to clarify whether the ARF-related decrease in the hepatic expression of drug-metabolizing enzymes is caused by an impairment in the translation/polypeptide formation process.ARF was induced with intramuscular glycerol injection. Dexamethasone was orally administered. Pooled liver microsomes from five rats were prepared with ultracentrifugation for each of four groups, namely, control and ARF rats, control rats with dexamethasone treatment and ARF rats with dexamethasone treatment.Hepatic drug-metabolizing activity was examined in an incubation study with the microsomes, where midazolam was employed as a substrate of cytochrome P450 (CYP) 3A enzymes. The hepatic protein and mRNA expressions of CYP3A23/3A1 and 3A2 enzymes were also evaluated.With dexamethasone treatment, the hepatic metabolic rate of midazolam increased 1.4 times in control rats, while it increased 19.6 times in ARF rats, reflecting the greater induction of hepatic protein expressions of CYP3A enzymes in ARF rats than in control rats.The hepatic protein expression process for CYP3A23/3A1 and 3A2 responds well to dexamethasone treatment in ARF rats, indicating that the translation/polypeptide formation process is not impaired in the presence of ARF.

In Vivo Study on Mechanism Underlying Increased Pharmacological Effects of Phenobarbital in Rats with Glycerol-Induced Acute Renal Failure.

The mechanism underlying the increased pharmacological effects of phenobarbital in rats with glycerol-induced acute renal failure (ARF) was examined. In the experiments, a surgical cannula was inserted in the lateral ventricle of the rats for phenobarbital infusion, and the ARF induction was performed by intramuscular administration of 50% glycerol. The onset time of anesthesia by phenobarbital was determined with the tail flick method. In addition, cerebral microsomes were prepared from excised cerebral cortices of sham and ARF rats, and the cerebral expression of the γ-aminobutyric acid (GABA)A receptor and two cation-chloride transporters, KCC2 and NKCC1, was evaluated by Western blotting, as their functions are involved in the anesthetic effects of phenobarbital. When phenobarbital was infused in the ventricle, anesthesia was induced 2.2-times faster in ARF rats than in sham rats, and there was no detectable increase in the cerebral expression of the GABAA receptor in ARF rats. It was additionally noted that the cerebral expression of KCC2 decreased, whereas that of NKCC1 was unaltered in ARF rats. These findings indicated that the anesthetic effects of phenobarbital are potentiated in ARF rats, probably due to imbalanced cerebral expression of KCC2 and NKCC1, suggesting that altered cation-chloride handling in nerve cells is associated.

Altered hepatic drug-metabolizing activity in rats suffering from hypoxemia with experimentally induced acute lung impairment.

1. Hepatic drug-metabolizing activity was investigated in vitro with liver microsomes prepared from rats suffering from hypoxemia with experimentally induced acute lung impairment (ALI). 2. Male Wistar rats received an intrabronchial administration of dilute hydrochloride solution for ALI induction. Pooled liver microsomes were prepared for the normal and ALI rats, and the hepatic drug metabolism mediated by cytochrome P450 (CYP) 3 A was examined in an incubation study with the microsomes. 3. The NADPH-dependent metabolism of midazolam significantly increases in ALI rats as compared with that in normal rats. Testosterone 6ß-hydroxylation was also observed to significantly increase in ALI rats. 4. When the hepatic expression of CYP3A proteins was examined, the protein expression of CYP3A1 was shown to significantly increase and that of CYP3A2 remained unaltered in ALI rats. The hepatic expression of NADPH-cytochrome P450 reductase (POR), a protein mediating electron transfer in CYP-mediated drug metabolism, was also revealed to significantly increases in ALI rats. 5. With the findings regarding the midazolam elimination, the hepatic drug-metabolizing activity seems to increase in response to acute hypoxemia, partly due to an altered expression of the CYP3A enzymes, and an augmented electron transfer with an increased POR expression is probably involved in the increase.

Similarities of Water-soluble Vitamin Components among Non-prescription Pharmaceutical Vitamin Products Generally Available on the Domestic Market.

Similarities among non-prescription pharmaceutical vitamin products generally available in community pharmacies were examined based on their vitamin components, and a chart was constructed to differentiate products to assist in appropriate product choice. In the analysis of the similarities, two hundred and seventy-six data entries on vitamin products were extracted from the database on the package inserts of the pharmaceutical products provided by the Pharmaceuticals and Medical Devices Agency, and they were reviewed for the amounts of vitamins they contained, in which the B vitamins, or vitamin B1, B2, B6, B12, and niacin, were considered as well as vitamins C and E. Pantothenic acid and L-Cysteine that are frequently used in combination with those vitamins are also taken into consideration. The data entries were then processed by classical multi-dimensional scaling to evaluate the inter-product similarities. As a result, it was shown that the products categorized as pharmaceutical nutrients and tonics containing vitamins (NTcV) are similar to one another, reflecting the fact that they are less characteristic regarding their vitamin components. As for the products in other categories, they were generally found to be featured for their unique content of vitamin components, and thereby, each category includes products with a wide range of variation. It was also indicated that some products categorized as vitamin B1, B2, and C products are less distinguishable from those categorized as NTcV. These findings will assist pharmacists to decide on an appropriate product for a customer following consultation.

Correlation between the Efficacy of Lamotrigine and the Serum Lamotrigine Level during the Remission Phase of Acute Bipolar II Depression: A Naturalistic and Unblinded Prospective Pilot Study.

Lamotrigine has acute antidepressant effects in patients with bipolar disorder. However, there is little information regarding appropriate serum levels of lamotrigine and the time until remission after the start of lamotrigine therapy in patients with bipolar II depression. This was a naturalistic and unblinded prospective pilot study. Twelve patients' depressive symptoms were evaluated using the Montgomery-Åsberg Depression Rating Scale (MADRS) at the start of treatment and at the time of remission, and blood samples were obtained at the time of remission. Mahalanobis distance was used to analyze the relationship between the MADRS improvement rate and the serum lamotrigine level. Furthermore, we calculated the Spearman's rank correlation coefficient for the relationship between the MADRS improvement rate and the serum lamotrigine level, and produced box plots of the serum lamotrigine level at remission and the time until remission. The Mahalanobis distance for the patient that was co-administered lamotrigine and valproic acid differed significantly from those of the other patients (p<0.001). There was no linear relationship between the serum lamotrigine level and the MADRS improvement rate among the patients that did not receive valproic acid. The median time from the start of lamotrigine therapy until remission was 6 weeks. The serum lamotrigine level does not have an important impact on the acute therapeutic effects of lamotrigine on bipolar II depression. In addition, we consider that different treatment options should be considered for non-responders who do not exhibit any improvement after the administration of lamotrigine for approximately 6 weeks.

Bortezomib combined with standard induction chemotherapy in Japanese children with refractory acute lymphoblastic leukemia.

Bortezomib has been shown to be effective and well-tolerated in patients with refractory acute lymphoblastic leukemia (ALL) in the Therapeutic Advances in Childhood Leukemia trial. However, the safety and efficacy of bortezomib have not been evaluated in Japanese pediatric patients. Here, we report the results of a clinical trial designed to evaluate the safety of bortezomib combined with induction chemotherapy in Japanese children with refractory ALL. A total of six patients with B-precursor ALL were enrolled in this study. Four-dose bortezomib (1.3 mg/m2/dose) combined with two standard induction chemotherapies was used. Prolonged pancytopenia (grade 4) was observed in all patients. Four of the six patients developed severe infectious complications. Peripheral neuropathy (grade 2) occurred in five patients. The individual plasma bortezomib concentration-time profiles were not related to toxicity and efficacy. Five patients were evaluable for response, and four patients achieved complete response (CR) or CR without platelet recovery (80%). In conclusion, four-dose bortezomib (1.3 mg/m2/dose) combined with standard re-induction chemotherapy was associated with a high risk of infectious complications induced by prolonged neutropenia, although high efficacy has been achieved for Japanese pediatric patients with refractory ALL. Attention must be given to severe infectious complications when performing re-induction chemotherapy including bortezomib.

In vivo application of chitosan to improve bioavailability of cyanocobalamin, a form of vitamin B12, following intraintestinal administration in rats.

The effect of chitosan on the intestinal absorption of cyanocobalamin (VB12), a stable form of vitamin B12, was investigated in vivo in rats, with the aim of improving the oral bioavailability of VB12 for anemia treatment in patients with gastrectomy. The bioavailability was evaluated based on the plasma concentration profile of VB12 following intraintestinal administration of the VB12 solution containing chitosan at various concentrations. The bioavailability of VB12 was 0.6±0.2% when the chitosan-free VB12 solution was administered, while it increased to 10.5±3.3% when chitosan was dissolved in the VB12 solution at a concentration of 1%. The bioavailability of VB12 increases with the chitosan concentration, in which chitosan seems to augment the amount of VB12 absorbed without affecting the absorption rate constant of VB12. It was also shown that the bioavailability of VB12 does not increase further when the degree of chitosan deacetylation is increased from 83 to 100% by substitutively employing the fully deacetylated chitosan. These findings suggest that the oral administration of VB12 with readily available chitosan may be a practical approach for anemia treatment in patients with gastrectomy.

Pharmaceutical properties of a low-substituted hydroxypropyl cellulose (L-HPC) hydrogel as a novel external dressing.

Controlling the moisture balance between exudates and their transpiration from the surface of wounded skin is important for healing. Low-substituted hydroxypropyl cellulose (L-HPC) hydrogel sheets (HGSs) possessing high water retention and water vapor transmission properties were prepared by neutralizing the highly viscous alkaline liquid of 7-10% L-HPC. Glycerol-impregnated L-HPC hydrogel sheets (L-HPC G-HGSs) were obtained by exchanging aqueous liquid in L-HPC HGSs. The physical characteristics required for wound dressings, i.e., mechanical strength, adhesive strength, and water retention properties, as well as the water vapor transmission (WVT) properties of L-HPC HGSs and L-HPC G-HGSs were evaluated. The mechanical strengths of L-HPC HGSs were enhanced with increases in the L-HPC content. The impregnation of glycerol in L-HPC HGSs yielded a significantly elasticated sheet. The adhesive strengths of L-HPC HGSs were significantly lower than those of commercial medical dressings. Water retention in L-HPC HGSs after being stored for 2h at 37°C was approximately 50%. The WVT rate of 7% L-HPC HGS was approximately 40g/m(2)/h, which was markedly higher than that of silicone gel type medical dressings. In conclusion, L-HPC HGSs are promising dressings that maintain an adequate moisture balance by transpiring excessive wound exudates with less damage to the healing wound.

Effect of carrageenan-induced acute peripheral inflammation on the pharmacokinetics and hepatic metabolism of midazolam in rats.

The effect of carrageenan-induced acute peripheral inflammation (API) on the pharmacokinetics of the hepatically metabolizing compound midazolam (MDZ) was investigated in rats. Rats were subcutaneously treated with λ-carrageenan in the hind paw to induce API. When MDZ was intravenously administered in male rats, it was demonstrated that the plasma concentration profile of MDZ slightly alters in API rats compared with that in normal rats, while the plasma concentrations of its metabolites, 4-hydroxy and 1'-hydroxy MDZ, are markedly reduced with delayed appearances in API rats. In the incubation study with rat liver microsomes, it was clearly indicated that the generation rates of the two metabolites decrease in API rats. Western blot analysis revealed that hepatic CYP3A1 expression increases, while CYP3A2 expression decreases in API rats. In female rats, in which CYP3A2 is barely expressed in the liver, MDZ metabolism is little affected by API. These findings indicate that the hepatic handling of a therapeutic compound varies with API, largely due to altered hepatic expression of the drug-metabolizing enzyme.

Effects of peritoneal dialysis on pharmacotherapy: a deductive pharmacokinetic-model approach to predict drug concentration profiles in plasma and peritoneal fluid.

The aim of this study was to present a deductive compartment pharmacokinetic (PK) model to predict the concentration profiles of drugs in plasma and peritoneal fluid in peritoneal dialysis (PD) rats. PK parameters of model drugs in normal and experimentally induced acute renal failure (ARF) rats not undergoing PD were obtained inductively in a common regression manner with a two-compartment model. In PD normal and ARF rats, PK parameters relating to the transfer of drugs to the peritoneal dialysate and the progress of renal failure were deductively modified to simulate the drug concentration-time profiles in plasma and in the peritoneal fluid in PD rats. The deductively introduced modifiers were the volume of distribution in the peripheral compartment, plasma protein binding, and solvent movement factor to the peritoneal fluid. Predicted profiles of tolbutamide, propranolol and cefazolin in PD normal and ARF rats were compared with the corresponding observed data. This minimal deductive approach yielded satisfactory accuracy in the prediction of both the plasma and peritoneal fluid concentrations of tolbutamide and propranolol.

Interspecies comparison of hepatic metabolism of six newly synthesized retinoid X receptor agonistic compounds possessing a 6-[N-ethyl-N-(alkoxyisopropylphenyl)amino]nicotinic acid skeleton in rat and human liver microsomes.

OBJECTIVE: The hepatic metabolism of six compounds newly synthesized as retinoid X receptor agonists was characterized in rat and human liver microsomes to examine the relationship between their hepatic metabolism profiles and side chain structures, considering the interspecies difference. MATERIALS AND METHODS: The compounds used have a 6-[N-ethyl-N-(3-alkoxy-4-isopropylphenyl)amino]nicotinic or 6-[N-ethyl-N-(4-alkoxy-3-isopropylphenyl)amino]nicotinic acid skeleton, in which the isopropoxy, isobutoxy or cyclopropylmethoxy group is employed for the alkoxy group. These compounds were incubated with the microsomes, and their Michaelis--Menten parameters were determined. The incubation study was also performed with various cytochrome P450 (CYP) inhibitors to examine their susceptibilities to the inhibitors. In addition, a molecular docking simulation was conducted to assess the compound's spatial configuration with the CYP isoform when necessary. RESULTS: The Michaelis--Menten parameters determined are comparable between rats and humans for the compounds having 3-isobutoxy, 4-isobutoxy, 4-isopropoxy and 4-cyclopropylmethoxy groups. However, it was indicated that all compounds except that having the 3-isobutoxy group are metabolized in a different manner between rats and humans. That is, the extent of the contribution of each CYP isozyme is different between those two species. A molecular docking simulation showed that the spatial configuration of the compound to be associated with CYP2D6 markedly changes depending on whether the isobutoxy group is situated at the 3- or 4-position. CONCLUSION: A slight difference in the side chain structures markedly alters the compound's metabolic profile, which amplifies the interspecies difference regarding the profile, increasing the difficulty in characterizing the profile in humans with the structural-property relationship and interspecies extrapolation.

Effect of carrageenan-induced acute peripheral inflammation on the electrolyte disposition to cerebrospinal fluid in rats.

To clarify whether peripheral inflammation has a remote effect on the central nervous system, the electrolyte disposition between the circulating blood and central nervous system was evaluated in rats with carrageenan-induced acute peripheral inflammation (API). λ-Carrageenan was subcutaneously injected in the hind paw of the rat, and lithium was utilized as a surrogate marker of sodium. When the plasma and cerebrospinal fluid (CSF) concentrations of lithium were examined following lithium being intravenously administered, it was revealed that the CSF concentration of lithium in API rats is reduced compared to that in normal rats, while the plasma concentration profile of lithium in API rats is indistinguishable from that in normal rats. The pharmacokinetic analysis showed that the lithium disposition from the plasma to CSF markedly decreased by 35.8% in API rats compared to that in normal rats. On the other hand, when lithium was immediately administered into the lateral ventricle, its elimination profiles in CSF were not different between normal and API rats. It is therefore probable that the lithium disposition from the plasma to CSF alters in API rats, reflecting the entry process of electrolytes from the circulating blood to brain tissue being suppressed in response to peripheral inflammation.

In vivo application of chitosan to facilitate intestinal acyclovir absorption in rats.

The effect of chitosan on the intestinal absorption of acyclovir (ACV) was evaluated in rats, and factors influencing its facilitative effect on the ACV absorption were examined. When ACV solution containing 1% chitosan with an average molecular weight of 150 kDa was administered into the upper jejunum, a significant increase in the plasma ACV concentration was observed, with the peak ACV concentration being eight times greater than that observed with the chitosan-free solution. The chitosan-free ACV solution, whose viscosity was adjusted to remain unchanged with polyethylene glycol, did not cause an increase in the plasma concentration, and neither did the chitosan-free solutions substitutionally containing low molecular cationic compounds, triethanolamine and kanamycin. When chitosan was digested with chitosanase to shorten its polycationic polysaccharide structure, chitosan subjected to 150-min digestion retained its facilitative effect on ACV absorption, but that subjected to 420-min digestion no longer caused facilitation, in which its average molecular weight was reduced to around 10 kDa. It is therefore indicated that intestinal ACV absorption can be facilitated with chitosan, and that it is necessary for chitosan to have a certain length of polycationic polysaccharide structure to exert such facilitation.

Comparative study on altered hepatic metabolism of CYP3A substrates in rats with glycerol-induced acute renal failure.

To examine the mechanism accounting for the diverse alteration of hepatic metabolism of CYP3A substrates observed with renal function being severely impaired, the hepatic drug metabolizing activity was evaluated using liver microsomes prepared from rats with glycerol-induced acute renal failure (ARF). Midazolam, nifedipine and rifabutin were employed as representative CYP3A substrates. When the Michaelis-Menten parameters, K(m) and V(max) , were examined in the incubation study, the K(m) values of midazolam and nifedipine in ARF rats were shown to decrease by 50.9% and 29.9% compared with the normal value, respectively. The V(max) values of midazolam and nifedipine in ARF rats also decreased by 49.3% and 28.0%, respectively, showing that their decreased K(m) values accompanied the decreased V(max) values. The parameters of nifedipine seemed to alter to a lesser extent than those of midazolam. As for rifabutin metabolism, the decrease in the K(m) value was observed in ARF rats, but it did not accompany the decrease in the V(max) value. Then, the hepatic expressions of the CYP3A subfamily were examined with western blotting using anti-CYP3A1 and anti-CYP3A2 antibodies. It was revealed that the hepatic expression of CYP3A2 decreased, while that of CYP3A1 was unaffected. Additionally, a band signal deduced to originate from CYP3A9 was clearly detected in ARF, but not in normal rats. Considering each substrate having different specificities for CYP3A subfamily member proteins, individual alterations of hepatic CYP3A subfamily expression seem to underlie the diverse alterations of hepatic metabolism of CYP3A substrates in ARF rats.

Pharmacodynamic characterization of nitric oxide-mediated vasodilatory activity in isolated perfused rat mesenteric artery bed.

Vasodilation profiles following a short-term infusion of nitric oxide (NO), acetylcholine (ACh), and sodium nitroprusside (SNP) into an isolated perfused mesenteric artery bed were analyzed in rats to examine their vasodilatory efficacy under physiological conditions. These compounds commonly increase the intracellular NO concentration to exert vasodilatory activity. In an experiment with exogenous NO infusion where 100 µl of 1 : 300 diluted NO-saturated solution (approx. 53 pmol of NO) was applied, the infusion caused transient vasodilation in a dose-dependent manner, with the peak vasodilation value being 74.7% of the maximum relaxation value. In experiments with ACh, the peak vasodilation value was 81.5% of the maximum at a dose of 60 pmol. The vasodilation profile of ACh was similar to that of NO infusion, but the ACh-induced vasodilation reduced at a slower rate than that induced by NO infusion. The vasodilatory activity of SNP was less potent than that of ACh, and its peak value was 62.8% of the maximum at a dose of 2000 pmol. However, SNP activity was augmented by removing the vascular endothelia of the mesenteric artery bed, and the peak value reached 67.3% of the maximum at a dose of 60 pmol. Pharmacodynamic analysis indicated that NO and ACh are equivalent regarding their vasodilatory efficacy, while the efficacy of SNP was less than 1% of theirs, as the arterial vascular endothelium impeded intracellular SNP-related NO generation, by which 95% of SNP's vasodilatory efficacy was negated. These findings will be helpful to understand factors influencing the therapeutic efficacy of vasodilators.

Pharmacokinetic properties of newly synthesized retinoid X receptor agonists possessing a 6-[N-ethyl-N-(3-alkoxy-4-isopropylphenyl)amino]nicotinic acid skeleton in rats.

OBJECTIVE: The pharmacokinetic properties of three newly synthesized retinoid X receptor (RXR) agonists were evaluated in rats to elucidate the structural factor influencing their pharmacokinetic properties. MATERIAL AND METHODS: Three RXR agonists possessing a common 6-[N-ethyl-N-(3-alkoxy-4-isopropylphenyl)amino]nicotinic acid skeleton and side chain structures that are slightly different from each other were prepared as we previously reported (Takamatsu et al., ChemMedChem, 2008; 3:780-787). The plasma concentration profiles of these compounds were evaluated following the intravenous and intra-intestinal administrations. Their hepatic metabolism was characterized using rat liver microsomes. RESULTS: Based on the plasma concentration profile, NEt-3IP (3-isopropoxy) was shown to have a distribution volume of 4.53 L/kg, and to be cleared from the body with an elimination half-time of 0.95 h. The bioavailability of NEt-3IP is 16.4%, whereas those of the isobutoxy analog NEt-3IB and the cyclopropylmethoxy analog NEt-3cPM are 46.5% and 22.6%, respectively. Subsequently, in the experiments using rat liver microsomes, the K(m) and V(max) values of NEt-3IP were determined as 7.85 µM and 0.48 nmol/min/mg protein, respectively. This K(m) value is nearly the same as those of NEt-3IB and NEt-3cPM, but the V(max) value is noticeably smaller. Additionally, it was revealed that the CYP family mainly metabolizing NEt-3IP is different from those metabolizing the other analogs. CONCLUSION: Based on these findings, the pharmacokinetic properties of the compounds possessing this type of the skeleton seem to be largely influenced by a slight modification of the side chain structure.

Empirical approach for improved estimation of unbound serum concentrations of valproic acid in epileptic infants by considering their physical development.

The unbound serum concentration of valproic acid (VPA) is closely related to its therapeutic efficacy. In epileptic infants, the unbound VPA concentration varies largely from patient to patient, being difficult to predict using the reported equations for older children. To establish an equation to estimate the unbound concentration in infants, we empirically characterized the relationship between total and unbound VPA concentrations, taking their growth and development into consideration. Data were retrospectively collected from archived clinical records of 30 epileptic infants aged 0-11 months old. The relationship between total and unbound VPA concentrations was analyzed according to the Langmuir equation, in which the patient's body weight, height, and body surface area were considered as physical development indices. Inter- and intra-individual variabilities in the VPA concentrations were also considered. It was shown that the unbound VPA concentration in infants is properly estimated when their body weights are taken into account, in which the parameter for the maximum binding site concentration (Bm) increases as the body weight increases, while that for the dissociation constant (Kd) is unaltered. Additionally, the relationship was shown to slightly change when the infants are concomitantly treated with VPA and the other antiepileptics. These findings provide useful information to adjust the VPA dosage to achieve optimal therapeutic efficacy in epileptic infants.

Altered electrolyte handling of the choroid plexus in rats with glycerol-induced acute renal failure.

The altered electrolyte handling of the choroid plexus was investigated in rats with acute renal failure (ARF) using lithium and rubidium as surrogate markers for sodium and potassium, respectively. Firstly, the transport of these two markers from the plasma to cerebrospinal fluid (CSF) was evaluated after they were concurrently injected into the femoral vein. As a result, their disposition from the plasma to CSF was shown to decrease in ARF rats, but the relationship profile between those two markers was not different from that observed in normal rats, indicating that the decreased disposition of lithium and rubidium occurs without affecting the stoichiometric balance. To clarify the mechanisms accounting for the decreased disposition, an inhibition study was then performed. When bumetanide, an inhibitor of the Na(+) /K(+) /2Cl(-) co-transporter, was directly introduced into the cerebroventricle prior to lithium and rubidium being intravenously administered, a marked increase in the markers' disposition was observed. However, such an increased disposition did not occur when bumetanide was injected into the femoral vein. Other inhibitors, such as amiloride for the Na(+) /H(+) exchanger and ouabain for Na(+) /K(+) -ATPase, did not show any effects on marker disposition regardless of the inhibitor being administered into either the cerebroventricle or femoral vein. These findings suggest that the decreased marker disposition in ARF rats is due to an increased efflux process of the choroid plexus mediated by the Na(+) /K(+) /2Cl(-) co-transporter. That is, electrolyte efflux from the CSF to plasma increases, and thereby the electrolyte influx from the plasma to CSF is counteracted.