Evaluation of Carbamazepine Pharmacokinetic Profiles in Mice with Kainic Acid-Induced Acute Seizures
Department of Biopharmaceutics, Faculty of Pharmaceutical Sciences, Doshisha Women's College of Liberal Arts, Kodo Kyotanabe, Kyoto 610-0395, Japan. Biological & Pharmaceutical Bulletin
(Impact Factor: 1.83).
01/2009; 31(12):2302-8. DOI: 10.1248/bpb.31.2302
The purpose of the present study was to evaluate the effect of kainic acid (KA)-induced acute seizures on the pharmacokinetic profiles of antiepileptic drug, carbamazepine (CBZ) in mice. Experimental acute seizure in mice was induced by intraperitoneal injection of KA (30 mg/kg), and mice were provided for experiments after 48 h of KA treatment. The portal plasma concentrations of CBZ and its metabolite carbamazepine-10,11-epoxide (CBZ-epo) had trends to decrease as compared to the control mice, whereas the brain CBZ and CBZ-epo concentrations was actually lower in KA treated mice. On the other hand, the exsorption of CBZ from blood to the intestinal lumen via P-glycoprotein (P-gp) in KA treated-mice was significantly increased in parallel with that of Rhodamine-123 (Rho123), a P-gp substrate. Western blotting analysis for intestinal and cerebral P-gp showed that the P-gp expression was induced in the KA-treated mice. The apparent brain-to-plasma concentration ratio (Kp) of CBZ in the KA-treated mice showed significant decrease but that of CBZ-epo did not. Moreover, in the KA-treated mice, the percentage of protein binding was significantly increased, and found to be an inverse proportion in the relationship between the Kp and protein binding of CBZ. In conclusion, the mechanism responsible for a decreased brain CBZ concentration in the KA-induced seizure mice is based on the up-regulation of P-gp function in tissues and plasma protein binding of CBZ.
Available from: Xiao-Dong Liu
- "Rho123, a typical substrate of P-GP, has been widely used as an index of P-GP mediated transport in in vitro and in vivo studies34, 35, 36, 37, 38, 39, 40. In the present study, Rho123 also served as a marker for evaluating P-GP function. "
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ABSTRACT: To investigate the changes of expression and function of P-glycoprotein (P-GP) in cerebral cortex, hippocampus, liver, intestinal mucosa and kidney of streptozocin-induced diabetic rats.
Diabetic rats were prepared via a single dose of streptozocin (65 mg/kg, ip). Abcb1/P-GP mRNA and protein expression levels in tissues were evaluated using quantitative real time polymerase chain reaction (QRT-PCR) analysis and Western blot, respectively. P-GP function was investigated via measuring tissue-to-plasma concentration ratios and body fluid excretion percentages of rhodamine 123.
In 5- and 8-week diabetic rats, Abcb1a mRNA levels were significantly decreased in cerebral cortices and intestinal mucosa, but dramatically increased in hippocampus and kidney. In liver, the level was increased in 5-week diabetic rats, and decreased in 8-week diabetic rats. Abcb1b mRNA levels were increased in cerebral cortex, hippocampus and kidney, but reduced in liver and intestinal mucosa in the diabetic rats. Western blot results were in accordance with the alterations of Abcb1a mRNA levels in most tissues examined. P-GP activity was markedly decreased in most tissues of diabetic rats, except kidney tissues.
Alterations in the expression and function of Abcb1/P-GP under diabetic conditions are tissue specific, Abcb1 specific and diabetic duration-dependent.
Available from: Dan Yao
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ABSTRACT: The multidrug resistance of epilepsy may result from the overexpression of P-glycoprotein, but the mechanisms are unclear. We investigated whether the overexpression of P-glycoprotein in the brains of subjects with pharmacoresistant epilepsy resulted from both drug effects and seizure activity.
Kindled rats were developed by injecting a subconvulsive dose of pentylenetetrazole (33 mg.kg(-1).day(-1), i.p.) for 28 days. Groups were then treated with an oral dose of phenobarbital (45 mg x kg(-1) x day(-1)) for 40 days. In accord with behavioural observations, P-glycoprotein activity in brain was assessed using brain-to-plasma concentration ratios of rhodamine 123. P-glycoprotein levels in the brain regions were further evaluated using RT-PCR and Western blot analysis. The distribution of phenobarbital in the brain was assessed by measuring phenobarbital concentrations 1 h following its oral administration.
The kindling significantly increased P-glycoprotein activity and expression. Good associations were found among P-glycoprotein activity, expression and phenobarbital concentration in the hippocampus. Short-term treatment with phenobarbital showed good anti-epileptic effect; the maximum effect occurred on day 14 when overexpression of P-glycoprotein was reversed. Continuous treatment with phenobarbital had a gradually reduced anti-epileptic effect and on day 40, phenobarbital exhibited no anti-epileptic effect; this was accompanied by both a re-enhancement of P-glycoprotein expression and decreased phenobarbital concentration in the hippocampus. P-glycoprotein function and expression were also increased in age-matched normal rats treated with phenobarbital.
The overexpression of P-glycoprotein in the brain of subjects with pharmacoresistant epilepsy is due to a combination of drug effects and epileptic seizures.
Available from: Shilpa D. Kadam
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ABSTRACT: Rodents eliminate antiepileptic drugs (AEDs) faster than humans, creating challenges for designing clinically relevant protocols. Half-lives of AEDs in immature mice are unknown. The pharmacokinetics of commonly used AEDs were examined in CD1 mice using a single-dose protocol at postnatal day 19. After intraperitoneal therapeutic dosing, blood serum concentrations spanning 1-48 h post-administration and corresponding brain tissue concentrations at 4 h were analyzed. Half-lives of valproate, phenobarbital, diazepam (and metabolites), phenytoin, and levetiracetam were 2.6, 15.8, 22.3, 16.3, and 3.2 h, respectively, compared to 0.8, 7.5, 7.7, 16.0, and 1.5 h reported for adult mice. Brain-to-blood ratios were comparable with adult ratios. AEDs tested had longer half-lives and maintained therapeutic plasma concentrations longer than reported in mature mice, making clinically relevant protocols feasible.
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