Journal of pharmaceutical sciences
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The purpose of this study was to assess the effect of mild heat and heat preconditioning on the uptake and permeability of a P-glycoprotein (P-gp) substrate, rhodamine 123 (R123), in a cell culture model of the blood-brain barrier (BBB). An immediate goal was to determine whether prior mild heat treatment could render brain microvessel endothelial cells more resistant to future heat stress and affect BBB drug permeation by future ultrasound-induced mild heat (USMH) treatment. To address this issue, the expression level of two proteins, P-gp and heat shock protein 70 (Hsp70), and their effects on uptake of R123 and permeability of R123 and [14C]-sucrose in combination with mild heat and P-gp modulator PSC833 during and after mild heat treatment in heat-preconditioned and heat-unconditioned bovine brain microvessel endothelial cell (BBMEC) monolayers were studied. ⋯ However, heat preconditioning is not sufficient to override the permeation-enhancing effects of mild heat because mild heat caused a significant increase in R123 uptake and permeability of R123 and [14C]-sucrose in both heat-preconditioned and heat-unconditioned cells. Because Hsp70 is known to play a major role in cellular repair and protective mechanisms, our results would imply a relative benign nature of mild heat treatment. Because heating produced by ultrasonic waves can be controlled and localized to a small volume within the tissue, the present results also suggest that USMH could play a pivotal role in the treatment of brain tumors and other brain-related diseases.
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Recently, our laboratory reported that intravenous immunoglobulin (IVIG) treatment increased antiplatelet antibody (7E3) clearance in a rat model of immune thrombocytopenic purpura (ITP). However, due to the multifaceted nature of IVIG therapy, the contribution of this increase in antiplatelet antibody clearance to the total therapeutic effect of IVIG was unclear. The purposes of the present study were to (1). develop a new, mechanistic model of immune gamma globulin (IgG) pharmacokinetics, (2). develop a pharmacokinetic/pharmacodynamic (PK/PD) model relating 7E3 concentrations to the platelet count time course observed following 7E3 treatment, and (3). use these mathematical models to gain insight into the significance of increased 7E3 clearance relative to the total effect of IVIG on 7E3-induced thrombocytopenia. ⋯ The model accurately captured antiplatelet antibody concentration versus time data in the presence and absence of IVIG therapy, in the rat, in 'wild-type' mice, and in 'knockout' mice lacking expression of the FcRn receptor. An indirect response PK/PD model was also developed, which accurately characterized 7E3 effects on platelet counts. Using these models, it was estimated that 50 +/- 11% of the total protective effect of IVIG in this acute model of ITP can be accounted for by IVIG effects on 7E3 disposition.
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Topical lidocaine has been recently marketed as a new treatment for post-herpetic neuralgia. The aim of our study was to characterize the absorption profile of and systemic exposure to lidocaine from patch and gel formulations in normal volunteers, patients with post-herpetic neuralgia, and patients with acute herpes zoster. ⋯ Systemic exposure to lidocaine and monoethylglycinexylidide (MEGX), the primary active metabolite of lidocaine, after application of lidocaine gel or patches was minimal in normal volunteers, patients with post-herpetic neuralgia, and patients with acute herpes zoster. Considering the benefit versus risk of topical lidocaine, systemic absorption and toxicity of lidocaine seems not to be a significant risk.
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Randomized Controlled Trial Clinical Trial
Effect of dexmedetomidine on propofol requirements in healthy subjects.
Dexmedetomidine-propofol pharmacodynamic interaction was evaluated in nine healthy subjects in a crossover design. Dexmedetomidine/placebo was infused using a computer-controlled infusion pump (CCIP) to maintain a pseudo-steady-state plasma concentration of 0.66 +/- 0.080 or 0 ng/mL, respectively. Forty-five minutes after the dexmedetomidine/placebo infusion was started, propofol was infused using a second CCIP to achieve a stepwise logarithmically ascending propofol concentration (1.00 to 13.8 microg/mL) profile. ⋯ The apparent EC50 values of propofol (EC50APP; concentration of propofol at which the probability of achieving a pharmacodynamic endpoint is 50% in the presence of dexmedetomidine concentrations observed in the current study; dexmedetomidine treatment) were 0.273, 0.544-0.643, and 3.89 microg/mL for the ability to hold a syringe, sedation scores, and motor response, respectively. Dexmedetomidine reduced propofol concentrations required for sedation and suppression of motor response. Therefore, the propofol dose required for sedation and induction of anesthesia may have to be reduced in the presence of dexmedetomidine.
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Comparative Study
Comparative effects of (SBE)7m-beta-CD and HP-beta-CD on the stability of two anti-neoplastic agents, melphalan and carmustine.
The purpose of this study was to evaluate and compare the potential use of two parenterally safe beta-cyclodextrins derivatives, (SBE)7m-beta-CD and HP-beta-CD, as solubilizers and stabilizers for melphalan and carmustine, two very unstable antineoplastic agents. Phase solubility and chemical stability of the compounds in the presence of the cyclodextrins were studied. UV, fluorescence, and several NMR techniques were used to probe the potential causes for the differences observed. ⋯ Qualitatively, however, the solubilizing potential was similar for the two cyclodextrins. The chemical stability studies indicate that both of the drugs had similar binding constants for both cyclodextrins; however, the intrinsic reactivities in the complexes were significantly lower with (SBE)7m-beta-CD than for HP-beta-CD. The main cause for this distinct difference appeared to correlate with differences in the site of binding and the polarity of the binding site.