J Pharm Pharmacol. 1999 May;51(5):565-76.
Characterization and in-vivo ocular absorption of liposome-encapsulated acyclovir.

Fresta M, Panico AM, Bucolo C, Giannavola C, Puglisi G.

Department of Pharmaceutical Sciences, University of Catania, Italy.

The potential of liposomes as an in-vivo ophthalmic drug delivery system for acyclovir was investigated. The drug-membrane interaction was evaluated by means of differential scanning calorimetry analysis. These experiments showed that acyclovir is able to interact with both positively and negatively charged membranes via electrostatic or hydrogen bonds. No interaction was observed with neutral membranes made up of dipalmitoylphosphatidylcholine. Different liposome preparation procedures were carried out to encapsulate acyclovir. The drug encapsulation mainly depends on the amount of water which the liposome system is able to entrap. In the case of multilamellar vesicles, charged systems showed the highest encapsulation efficiency. No particular difference in the encapsulation efficiency was observed for oligolamellar vesicles prepared with the reverse-phase evaporation technique. Oligolamellar liposomes showed the highest acyclovir encapsulation parameters and had release profiles similar to those of multilamellar liposomes. In-vivo experiments using male New Zealand albino rabbits were carried out to evaluate the aqueous humour concentration of acyclovir bioavailability. The most suitable ophthalmic drug delivery system was oligolamellar systems made up of dipalmitoylphosphatidylcholine-cholesterol-dimethyldioctadecyl glycerole bromide (7:4:1 molar ratio), which presented the highest encapsulation capacity and were able to deliver greater amounts of the drug into the aqueous humour than a saline acyclovir solution or a physical liposome/drug blend.

Online pharmacy ref source - acyclovir: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10411216&dopt=Abstract acyclovir Zovirax




New Microbiol. 1999 Oct;22(4):309-14.
Acyclovir treatment prevents varicella-zoster virus replication in PBMC during viremia.

Wolff MH, Schunemann S.

Institute of Microbiology and Virology, University of Witten/Herdecke, Germany.

The most effective antiviral therapy of varicella and zoster has become acyclovir. Using polymerase chain reaction specific for VZV ORF 14, ORF 29, ORF 63 as well as nucleic acid sequence-based amplification (ORF 63, ORF 68) we tested PBMC of patients with VZV-associated diseases for the presence of viral DNA and RNA, respectively. In PBMC of patients treated with acyclovir neither DNA nor RNA was detectable already one day after the onset of therapy. In three blood sample pairs from zoster patients we were able to detect viral nucleic acid before but not after acyclovir treatment. These results confirm clinical and epidemiological data. It can be concluded that treatment with acyclovir prevents VZV replication in peripheral blood mononuclear cells.

Online pharmacy ref source - acyclovir: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10555200&dopt=Abstract acyclovir Zovirax

ucsd.edu

Acyclovir triphosphate is a potent inhibitor of hepatitis B virus DNA polymerase, but acyclovir treatment provides no benefit in patients with hepatitis B virus infection. This is due in part to the fact that hepatitis B virus, unlike herpes simplex virus, does not code for a viral thymidine kinase which catalyzes the initial phosphorylation of acyclovir. We synthesized 1-O-octadecyl-sn-glycero-3-phospho (3-P)-acyclovir and found that it was highly active in reducing hepatitis B virus replication in 2.2. 15 cells, while acyclovir was inactive. The greater antiviral activity of 1-O-octadecyl-sn-glycero-3-P-acyclovir appeared to be due to liver cell metabolism of the compound to acyclovir monophosphate (K. Y. Hostetler et al., Biochem. Pharmacol. 53:1815-1822, 1997). However, a closely related compound without a hydroxyl group at the sn-2 position of glycerol, 1-O-hexadecylpropanediol-3-P-acyclovir, was more active and selective in 2.2.15 cells in vitro. In this study, we treated woodchucks chronically infected with woodchuck hepatitis virus with increasing oral doses of 1-O-hexadecylpropanediol-3-P-acyclovir and assessed the response to therapy versus acyclovir or a placebo. At a dosage of 10 mg/kg of body weight twice a day, the test compound significantly inhibited viral replication in vivo, as indicated by a 95% reduction in serum woodchuck hepatitis virus DNA levels and by a 54% reduction in levels of woodchuck hepatitis virus replicative intermediates in the liver. Higher doses were somewhat less effective. In contrast, 20 mg of acyclovir/kg twice daily, a 5. 3-fold-higher molar dosage, had no demonstrable activity against woodchuck hepatitis virus. Oral 1-O-hexadecylpropanediol-3-P-acyclovir appeared to be safe and effective in chronic woodchuck hepatitis virus infection.

Online pharmacy ref source - acyclovir: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10858362&dopt=Abstract acyclovir Zovirax

UNM.edu

During childhood chickenpox, varicella-zoster virus becomes latent in neurons of the dorsal root or trigeminal ganglia. Shingles results years to decades later from a breakdown of viral latency within a ganglion and subsequent virus spread to the skin producing a unilateral dermatomal vesicular rash accompanied by segmental pain. Treatment with famciclovir, valacyclovir, and high dose acyclovir is beneficial if started within the first 3 days of the rash. All three drugs can be given orally, are equally effective, shorten the duration of viral shedding and time to healing of the rash by 1 to 2 days, and lessen the intensity and duration of the acute neuritic pain. Famciclovir and valacyclovir have more convenient dosing schedules (three times daily) compared to acyclovir (five times daily). Mild cases of shingles in younger healthy individuals often do not require any antiviral treatment. Pain in shingles may have burning, lancinating, or allodynic qualities, ranges in intensity from mild to unbearable, and lasts 2 to 8 weeks. Pain treatment varies on the type and intensity of pain experienced. In a few patients, post-herpetic neuralgia develops and the dermatomal pain persists for months to years. Effective treatment of post-herpetic pain is often difficult.

Online pharmacy ref source - acyclovir: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11487454&dopt=Abstract acyclovir Zovirax[PubMed - as supplied by publisher]




J Microencapsul. 2001 Sep-Oct;18(5):559-65.
In vitro modified release of acyclovir from ethyl cellulose microspheres.

Cheu SJ, Chen RR, Chen PF, Lin WJ.

School of Pharmacy, College of Medicine, National Taiwan University, Taipei.

The aim of this study was to demonstrate a sustained-release microparticulate dosage form for acyclovir via an in vitro study. Ethyl cellulose was selected as a model encapsulation material. All of the microspheres were prepared by an oil-in-water solvent evaporation technique. A 2(3) full factorial experiment was applied to study the effects of the viscosity of polymer, polymer/drug ratio, and polymer concentration on the drug encapsulation efficiency and the dissolution characteristics. The encapsulation efficiency of acyclovir in microspheres was in the range of 20.0-56.6%. Increase in the viscosity of ethyl cellulose and the ratio of CH2Cl2/ethyl cellulose increased drug encapsulation efficiency. The drug continuously released from microspheres for at least 12 h, and the release rate depended on the pH of the release medium. The sustained release characteristic was more prominent in the simulated intestine fluid than in the simulated gastric fluid. A faster release of drug was observed when a high viscosity polymer was used. The decomposition of acyclovir significantly decreased when encapsulated by ethyl cellulose, especially when stored at 37 and 50 degrees C.

Online pharmacy ref source - acyclovir: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11508761&dopt=Abstract acyclovir Zovirax