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leo-pharma.com

L-Valacyclovir, a prodrug of acyclovir, is a substrate for the peptide transporter (PepT1) in the intestinal mucosa, which accounts for its higher than expected oral bioavailability. The substrate activity of L-valacyclovir for PepT1 is surprising, particularly when one considers that the molecule has the structural features of a nucleoside rather than a peptide. In an attempt to better understand the structure-transport relationships (STR) for the interactions of L-valacyclovir with PepT1, analogs of this molecule with structural changes in the guanine moiety were synthesized and their substrate activity for PepT1 in Caco-2 cell monolayers was determined. The analogs synthesized include those that had the guanine moiety of L-valacyclovir substituted with purine, benzimidazole, and 7-azaindole. All three analogs (purine, benzimidazole, and 7-azaindole) exhibited affinity for PepT1 in binding studies, but only the purine analog (as the L-valine ester) showed PepT1-associated transcellular transport across Caco-2 cell monolayers. The benzimidazole and 7-azaindole analogs (as their L-valine esters) were rapidly metabolized by esterase when applied to the apical surface of Caco-2 cells, which probably explains their low penetration as the intact prodrugs via PepT1.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12113886&dopt=Abstract




Clin Infect Dis. 2002 Aug 1;35(3):254-60. Epub 2002 Jul 10.
Outcome of and prognostic factors for herpes simplex encephalitis in adult patients: results of a multicenter study.

Raschilas F, Wolff M, Delatour F, Chaffaut C, De Broucker T, Chevret S, Lebon P, Canton P, Rozenberg F.

Laboratoire de Virologie, Hopital Saint-Vincent-de-Paul, and Service de Reanimation des Maladies Infectieuses, Hopital Bichat-Claude Bernard, Paris, France.

Management of herpes simplex encephalitis (HSE) has been considerably improved by the availability of acyclovir therapy and rapid polymerase chain reaction (PCR)-based diagnostic assays. Prognostic factors for this rare affliction are, however, misestimated. We conducted a large retrospective multicenter study that included 93 adult patients in whom HSE was diagnosed by PCR from 1991 through 1998 and who were treated with intravenous acyclovir. Among the 85 patients assessed at 6 months, 30 (35%) had a poor outcome, which led to death in 13 patients (15%) and severe disability in 17 (20%). The outcome was favorable for 55 patients (65%). A multivariate analysis identified 2 factors that were found to be independently associated with poor outcome: a Simplified Acute Physiology Score II >/=27 at admission and a delay of >2 days between admission to the hospital and initiation of acyclovir therapy. Early administration of antiviral therapy is the only parameter that can be modified to improve the prognosis of patients with HSE.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12115090&dopt=Abstract




J Neurovirol. 2000 Feb;6(1):25-32.
Herpes simplex replication and dissemination is not increased by corticosteroid treatment in a rat model of focal Herpes encephalitis.

Thompson KA, Blessing WW, Wesselingh SL.

Infectious Diseases Unit, School of Medicine, Monash University, Victoria, Australia.

Neurological damage in Herpes simplex type 1 encephalitis results from neuronal cell death secondary to viral invasion, and from inflammatory changes and cerebral oedema secondary to the immune response to the virus. Corticosteroids could have an important role in the management of Herpes simplex encephalitis because their anti-inflammatory action reduces cerebral oedema. However their use has been limited by concerns that their immunosuppressive actions could increase viral replication and spread. The present study examined this issue in a rat model in which injection of HSV-1 into the cervical vagus nerve produced a well-defined focal encephalitis, characterised by an orderly progression of the virus through central neural pathways connected with vagal afferent termination sites in the medulla oblongata. After injection of HSV-1, rats were treated twice a day, either with vehicle (saline, 400 microl i.p.), with acyclovir (30 mg/kg i.p.), with dexamethasone (5 mg/kg i.p.), or with both acyclovir and dexamethasone. Animals were sacrificed after 72 h, and viral load in different brain regions was quantified by computer-assisted measurement of the area occupied by immunohistochemical reaction product. Treatment with acyclovir reduced viral load to 17 +/- 5% of the saline value (P < 0.01). After dexamethasone treatment, the viral load (63 +/- 13% of the saline value) was also reduced (P < 0.05). Treatment with both acyclovir and dexamethasone reduced viral load to 26 +/- 8% of the saline value (P < 0.01 compared with saline, and P > 0.05 compared to acyclovir alone). Our results confirm the effectiveness of acyclovir in a new model of HSV-1 infection, and provide evidence that corticosteroids do not inhibit the antiviral action of acyclovir. In addition corticosteroids may decrease the extent of infection in their own right. The acute time course studied in our model parallels the time course of acute Herpes simplex encephalitis in humans. Our data suggests that corticosteroids are not detrimental when combined with acyclovir in the management of this condition.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10786994&dopt=Abstract













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