Drugs online research references
Tierarztl Prax. 1994 Dec;22(6):542-53.
[A herpesvirus-caused enzootic--Pacheco's parrot disease--in a psittacine collection]
[Article in German]
Eskens U, Kaleta EF, Unger G.
Staatlichen Medizinal-, Lebensmittel- und Veterinaruntersuchungsamt Mittelhessen, Justus-Liebig-Universitat, Giessen.
After the official confirmation of psittacosis in a collection of psittacine birds a total of 40 of them died during treatment with tetracycline. 36 of them underwent post mortem examination. From 33 birds the causative herpesvirus of Pacheco's parrot disease (PPD) was isolated and/or a non-purulent hepatitis diagnosed, the latter a characteristic for PPD. The cause of the outbreak was assumed to be a latent herpesvirus infection of individual birds which was activated by various stress factors during the psittacosis treatment. The macroscopic and histologic lesions, the results of virological investigations and the in vitro effect of acyclovir on the multiplication of the isolated herpes virus are described.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7716752&dopt=Abstract
J Pharm Sci. 2001 May;90(5):617-24.
Chemical stability, enzymatic hydrolysis, and nasal uptake of amino acid ester prodrugs of acyclovir.
Yang C, Gao H, Mitra AK.
Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri, 5005 Rockhill Road, Kansas City, Missouri 64110, USA.
The objective of this work was to improve nasal absorption of relatively impermeable small drug molecules via an amino acid prodrug approach. Acyclovir was selected as a model drug. L-Aspartate beta-ester, L-lysyl, and L-phenylalanyl esters of acyclovir were synthesized to investigate their effectiveness in enhancing nasal absorption of acyclovir. A stability study was conducted in phosphate buffer under various pH conditions at 25 and 37 degrees C. Enzymatic hydrolysis in rat nasal washings and plasma was conducted at 37 degrees C. A rat in situ nasal perfusion technique was utilized in this investigation to examine the rate and extent of nasal absorption of amino acid prodrugs. The remaining analyte concentrations in the nasal perfusate were quantitated by reversed-phase high-performance liquid chromatography. The results revealed that the L-lysyl and L-phenylalanyl esters were less stable than L-aspartate beta-ester. The stability of all three esters decreased with increasing pH and temperature. L-phenylalanyl ester is highly susceptible to plasma esterases, with an in vitro half-life 1.33 min. The rat in situ nasal perfusion study revealed that the extent of nasal absorption of acyclovir, L-lysyl and L-phenylalanyl esters was not significant (p < 1%). L-Aspartate beta-ester was absorbed to the extent of approximately 8% over 90 min of perfusion at an initial drug concentration of 100 microM. Nasal absorption of L-aspartate beta-ester of acyclovir was inhibited by L-asparagine but not by a dipeptide glycylsarcosine (Gly-Sar). The enhancement of acyclovir nasal absorption from the L-aspartate beta-ester prodrug suggests that nasal uptake of this prodrug probably involves an active transport system. Copyright 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11288106&dopt=Abstract
alpharma.dk
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 degrees C-70 degrees C). Acyclovir can be incorporated in high amounts (approximately 40% w/w) without causing phase transition, as is shown in polarized light. This is probably because of its low solubility (approximately 0.11% 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 microg/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.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11794810&dopt=Abstract
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