- Topical iontophoretic delivery of ionizable, biolabile aciclovir prodrugs: A rational approach to improve cutaneous bioavailability
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The objective was to investigate the topical iontophoretic delivery of a series of amino acid ester prodrugs of aciclovir (ACV-X, where ACV = aciclovir and X = Arg, Gly, Ile, Phe, Trp and Val) as a means to enhance cutaneous delivery of ACV. The newly synthesized prodrugs were characterized by 1H NMR and high resolution mass spectrometry. Analytical methods using HPLC-UV were developed for their quantification and each method was validated. Investigation of solution stability as a function of pH showed that all ACV-X prodrugs were relatively stable in acid conditions at pH 2.0 and pH 5.5 for up to 8 h but susceptible to extensive hydrolysis at pH 7.4 and under alkaline conditions (pH 10). No ACV-X hydrolysis was observed after contact for 2 h with the external surface of porcine stratum corneum. However, there was significant hydrolysis following contact with the dermal surface of dermatomed porcine skin, in particular, for ACV-Arg. Passive transport of ACV and ACV-X prodrugs from aqueous solution after 2 h was below the limit of detection. Iontophoresis of ACV at 0.5 mA/cm2 for 2 h led to modest ACV skin deposition (QDEP,ACV) of 4.6 ± 0.3 nmol/cm2. In contrast, iontophoresis of ACV-X prodrugs under the same conditions produced order of magnitude increases in cutaneous deposition of ACV species, that is, QDEP,TOTAL = QDEP,ACV + QDEP,ACV-X. QDEP,TOTAL for ACV-Gly, ACV-Val, ACV-Ile, ACV-Phe, ACV-Trp and ACV-Arg was 412.8 ± 44.0, 358.8 ± 66.8, 434.1 ± 68.2, 249.8 ± 81.4, 156.1 ± 76.3, 785.9 ± 78.1 nmol/cm2, respectively. The extent of bioconversion of ACV-X to ACV in the skin was high and the proportion of ACV present ranged from 81% to 100%. The skin retention ratio, a measure of the selectivity of ACV species for deposition over permeation after iontophoretic delivery of ACV-X prodrugs, was dependent on both the rate of transport and the susceptibility to hydrolysis of the prodrugs. Skin deposition of ACV and its six prodrugs were investigated further as a function of current density (0.125, 0.25 and 0.5 mA/cm2); the effect of duration of current application (5, 10, 30, 60 and 120 min) was evaluated using ACV-Arg and ACV-Ile. Iontophoresis of ACV-Arg and ACV-Ile at 0.25 mA/cm2 for only 5 min resulted in the deposition of appreciable amounts of ACV (36.4 ± 5.7 nmol/cm2 and 40.3 ± 6.1 nmol/cm2, respectively), corresponding to supra-therapeutic average concentrations in skin against HSV-1 or HSV-2. The results demonstrated that cutaneous bioavailability of ACV could be significantly improved after short-duration iontophoresis of ionizable, biolabile ACV-X prodrugs.
- Chen, Yong,Alberti, Ingo,Kalia, Yogeshvar N.
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p. 103 - 113
(2016/01/15)
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- Liquid chromatographic resolution of amino acid esters of acyclovir including racemic valacyclovir on crown ether-based chiral stationary phases
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Valacyclovir, a potential prodrug for the treatment of patients with herpes simplex and herpes zoster, and its analogs were resolved on two chiral stationary phases (CSPs) based on (3,3′-diphenyl-1,1′-binaphthyl)-20-crown-6 covalently bonded to silica gel. In order to find out an appropriate mobile phase condition, various mobile phases consisting of various organic modifiers in water containing various acidic modifiers were applied to the resolution of valacyclovir and its analogs. When 30% acetonitrile in water containing any of 0.05 M, 0.10 M, or 0.15 M perchloric acid was used as a mobile phase, valacyclovir and its analogs were resolved quite well on the two CSPs with the separation factors (α) in the range of 2.49~6.35 and resolutions (RS) in the range of 2.95 ~ 12.21. Between the two CSPs, the CSP containing residual silanol protecting n-octyl groups on the silica surface was found to be better than the CSP containing residual silanol groups.
- Ahn, Seong Ae,Hyun, Myung Ho
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p. 268 - 273
(2015/03/18)
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- Crystalline forms of valacyclovir hydrochloride
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Provided are novel crystalline forms of valacyclovir hydrochloride, in particular a novel hydrated form of valacyclovir hydrochloride having about 6% to about 10% by weight water. Also provided are methods for making the novel crystalline forms.
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- Crystalline forms of valacyclovir hydrochloride
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Provided are novel polymorphs and pseudopolymorphs of valacyclovir hydrochloride and pharmaceutical compositions containing these. Also provided are methods for making the novel polymorphs and pseudopolymorphs, which include valacyclovir hydrochloride monohydrate and valacyclovir hydrochloride dihydrate.
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- Azetidinone derivatives for the treatment of HCMV infections
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A compound of formula 1: wherein Y is S or O; R1is C1-6alkyl; (C0-6alkyl)aryl; (C0-6alkyl)Het; or R1is an amino acid analog or dipeptide analog of the formula: wherein R2is H, C1-10alkyl; or an amide or ester group; A is C6-10aryl, Het or CH—R3wherein R3is C1-6alkyl or (C0-4alkyl)aryl; and Z is H, C1-6alkyl, or an acyl; R4is hydrogen, lower alkyl, methoxy, ethoxy, or benzyloxy; and R5is alkyl, cycloalkyl, carboxyl group; an aryl; Het or Het(lower alkyl); or R4and R5together with the nitrogen atom to which they are attached form a nitrogen containing ring optionally substituted with phenyl or C(O)OCH2-phenyl, said phenyl ring optionally mono- or di-substituted with among others C(O)OR7wherein R7is lower alkyl or phenyl(lower alkyl); or a therapeutically acceptable acid addition salt thereof which compounds are useful in the treatment of HCMV infections.
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- Therapeutic valine esters of acyclovir and pharmaceutically acceptable salts thereof
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The present invention relates to certain amino acid exters of the purine nucleoside acyclovir, pharmaceutically acceptable salts thereof and their use in the treatment of herpes virus infections. The invention also includes pharmaceutical formulations and processes for the preparation of such compounds.
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