Effect of chitosan glutamate,carbomer 974P,and EDTA on the in vitro Caco-2 permeability and oral pharmacokinetic profile of acyclovir in rats

Background: Chitosan glutamate and polyacrylic acid (e.g., carbomer 974P) are known to modulate the tight junctions in the intestinal wall and increase permeability and blood exposure of drugs absorbed orally by the paracellular route. Aim: To assess the impact of chitosan glutamate and carbomer 974P on the absorption of paracellularly absorbed model drug, acyclovir, in vitro and in rat in vivo. Methods: The influence of chitosan glutamate and carbomer 974P (alone and in combination with EDTA–Na2) on the in vitro Caco-2 permeability and oral pharmacokinetic profile in the rat of acyclovir was investigated. Results: In the presence of chitosan glutamate, the apparent permeability of acyclovir across Caco2 monolayer increased 4.1 times relative to control. This increase was accompanied by a significant (～60%) decrease in transepithelial electrical resistance values indicating opening of the tight junctions in the cell monolayer. In rat, chitosan glutamate doubled oral bioavailability of acyclovir and tripled the amount of acyclovir excreted unchanged into urine. In contrast, the effect of carbomer 974P was not statistically significant at 5% level. Conclusions: In conclusion, chitosan glutamate (1–3%) and chitosan glutamate (1%)/EDTA–Na2 (0.01%) are effective excipients to increase permeability of acyclovir across Caco-2 cell monolayers and the oral absorption in the rat in vivo.     

阿昔洛韦在超临界CO2中的溶解度与关联

药物微粒化可改善其溶出度,提高生物利用度。为应用超临界流体技术制备阿昔洛韦(Acyclovir)微粒,用静态法测定了在313．15～413．15K,10．0～30．0MPa下阿昔洛韦在超临界CO2中的溶解度。阿昔洛韦的溶解度较小,在10^-5～10^-7(摩尔分率)之间,溶解度随着温度和压力的升高而增大,不存在文献报道的反向区。采用P-R方程对溶解度数据进行关联,平均相对误差为10．0％。     

Formulation and Pharmacokinetic Studies of Acyclovir Controlled-Release Capsules

Acyclovir controlled-release capsules (CRCs) were prepared by a three-step process: [1] melt granulation of acyclovir; [2] coating of granules with ethylcellulose; [3] incorporation of coated granules into hard gelatin capsules. In vitro release experiments showed that the main factors affecting the release rate were the mean particle size of the acyclovir raw material and the amount of coating material applied. Release of acyclovir from the capsules was in accordance with the Higuchi equation. Pharmacokinetic studies in dogs after oral administration of acyclovir controlled-release capsules showed that the formulation was successful in providing slow release of acyclovir and was superior to a commercially available controlled-release formulation.     

Mucoadhesive plasticized system of branched poly(lactic-co-glycolic acid) with aciclovir

Commercially available antibacterial semisolid preparations intended for topical application provide only short-term drug release. A sustained kinetics is possible by exploitation of a biodegradable polymer carrier. The purpose of this work is to formulate a mucoadhesive system with aciclovir (ACV) based on a solid molecular dispersion of this drug in poly(lactic-co-glycolic acid) branched on tripenterythritol (PLGA/T). The ACV incorporation into PLGA/T was carried out either by solvent method, or melting method, or plasticization method using various plasticizers. The drug–polymer miscibility, plasticizer efficiency and content of residual solvent were found out employing DSC. Viscosity was measured at the shear rate range from 0.10 to 10.00?s^?1 at three temperatures and data were analyzed by Newtonian model. The mucoadhesive properties were ascertained in the tensile test on a mucin substrate. The amount of ACV released was carried out in a wash-off dissolution test. The DSC results indicate a transformation of crystalline form of ACV into an amorphous dissolved in branched polyester carrier, and absence of methyl formate residuals in formulation. All the tested plasticizers are efficient at T_g depression and viscosity decrease. The non-conventional ethyl pyruvate possessing supportive anti-inflammatory activity was evaluated as the most suitable plasticizer. The ACV release was strongly dependent on the ethyl pyruvate concentration and lasted from 1 to 10 days. The formulated PLGA/T system with ACV exhibits increased adhesion to mucosal hydrophilic surfaces and prolonged ACV release controllable by degradation process and viscosity parameters.     

Calculation procedures and HPLC method for analysis of the lipophilicity of acyclovir esters

Acyclovir (ACV) belongs to a class of drugs with low bioavailability. Selected ACV esters including acetyl (Ac-), isobutyryl (iBut-), pivaloyl (Piv-), ethoxycarbonyl (Etc-) and nicotinoyl (Nic-) were synthesized, and their lipophilicity was determined by the high-performance liquid chromatography (HPLC) RP method. Statistical analyses of the comparative values of log?P and clog?P were carried out using computational methods. It was proved that the AC log?P algorithm can be useful for the analysis of these compounds and has a statistically justified application in the assessment of the quantitative structure–activity relationship. Moreover, the lipophilicity determined by the HPLC method appears as follows: ACV?相似文献   

抗病毒药阿昔洛韦的合成改进

鸟嘌呤、六甲基二硅氮烷和（NH4）2SO4回流反应18h,浓缩,溶于苯,过滤后与AcOCH2CH2OCH2Br在Hg(CN)2的催化作用下缩合,水解得9－[（2－乙酰氧乙氧基）甲基]鸟嘌呤（1）,1最后与CH2NH2反应制得阿昔洛韦。总收率为72．3％。     

Effects of Triton X-100 and Acyclovir on Human Serum Albumin Structure

The effects of acyclovir and Triton X-100 on the behavior of human serum albumin (HSA) in a acyclovir/HSA/H₂O system were studied by UV spectroscopy, fluorescence spectroscopy and polarization, conductivity, zeta potential, and circular dichroism. Both acyclovir and Triton X-100 affect the structure and behavior of HSA. The intrinsic fluorescence intensity, net charge of HSA and the conductivity of the system increase initially with increased acyclovir concentration, and the zeta potential of HSA decreases initially. The effects of Triton X-100 are similar to those of acyclovir except for the non-radiant energy transfer in the quenching process of Triton X-100 to HSA. The associating site of HSA with acyclovir is the same as that of HSA with Triton X-100.

Release Kinetics of Acyclovir from a Suspension of Acyclovir Incorporated in a Cubic Phase Delivery System

Acyclovir is a widely used agent in the treatment of herpes virus infections of the skin, but owing to its poor physicochemical properties in terms of bioavailability and suboptimal formulations, the treatment is far from optimal. The liquid crystalline cubic phase system has been reported to act as a bioadhesive drug delivery system. In the present study, acyclovir was suspended in a cubic phase of glycerol monooleate (GMO) and water 65%:35% w/w, and the phase behavior and release kinetics were examined. X-ray diffraction and differential scanning calorimetry (DSC) measurements demonstrated that the cubic phase containing 1%-10% (w/w) acyclovir retains its phase condition in the temperature range investigated (20°C-70°C). Acyclovir can be incorporated in high amounts (∼40% w/w) without causing phase transition, as is shown in polarized light. This is probably because of its low solubility (∼0.1% w/w) in the cubic phase. The release characteristics of acyclovir incorporated as a suspension (1%-5% w/w) into a cubic phase were investigated using Franz diffusion cells. Acyclovir was quantified by high-performance liquid chromatography (HPLC). The drug was readily released from the system, and the release increased with the initial drug load concentration. About 25%-50% was released after 24 h. The release is dependent on the square root of time, and the kinetics can be described by the Higuchi theory. The rate-limiting step in the release process is most likely diffusion. The suggested theory is further supported by identical release data obtained for micronized and nonmicronized acyclovir. The fluxes for 1% and 5% w/w were 380 and 900 μg/h^1/2, respectively. Comparison of the release rates of acyclovir delivered from a cubic phase and from the commercial product, Zovir® cream, showed the rate to be six times faster from the cubic phase. The results indicate that the cubic phase is a promising drug delivery system for acyclovir.     

Improved Dissolution Behavior of Fenbufen by Spherical Crystallization

Fenbufen is an analgesic, antipyretic and anti-inflammatory drug that is characterized by poor water solubility, a defect increased by very low wettability. Poor water solubility, particularly at low pH, could decrease absorption in the upper part of the gastrointestinal tract, which would be inconvenient for good bioavailability. Different spherical crystallization processes have been considered as methods to improve fenbufen dissolution behavior. A two-solvent system, in the presence of a bridging liquid, is the only method capable of producing spherical fenbufen crystals. In a first step, fenbufen solubility was considered in different solvents. The drug crystals formed were typically needle shaped. This characteristic was considered as a favorable parameter to obtain spherical crystals. After the selection of the best fenbufen solvent, several ratios of solvent (S)–nonsolvent (NS) (tetrahydrofuran [THF]–demineralized water) were studied. The addition of a bridging liquid (isopropyl acetate) improved spherical crystallization. The results from this method were reproducible batch to batch. The spherical crystals obtained showed a clear improvement in dissolution capacity, probably due to better wettability. Dissolution studies were then carried out on these spherical crystals stored for 1 month at different relative humidities (RHs). The dissolution profiles remained unchanged.     

Comparative Permeability of Some Acyclovir Derivatives Through Native Mucus and Crude Mucin Dispersions

The permeability of some guanine derivatives (acyclovir [ACV], deoxyacyclovir [DCV], and their N-acetyl congeners) through native porcine mucus and crude porcine mucin dispersions (30% and 50% w/v) was investigated in two-compartment dialysis cells. High correlation between apparent permeability coefficients P_app of tested substances determined in these two models was observed, although the examined compounds permeated faster through the native mucus. It was also established that P_app values decrease with increasing hydrophilicity and molecular mass of the tested substances. Furthermore, the influence of some substances that affect mucus structure (cysteine, N-acetylcysteine [NCY], sodium taurocholate [ST], and sodium chloride) on the permeation rate of the examined compounds through mucus and mucin dispersions was examined. It was shown that the P_app values of guanine derivatives were generally lower after the addition of these substances to the native mucus and mucin dispersions, although the lowering effect was more pronounced in the case of native mucus.