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Multiple oral dosing of valacyclovir in horses and ponies
Author(s) -
GARRÉ B.,
BAERT K.,
NAUWYNCK H.,
DEPREZ P.,
DE BACKER P.,
CROUBELS S.
Publication year - 2009
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.2008.01025.x
Subject(s) - dosing , mucus , cerebrospinal fluid , horse , medicine , nasal administration , regimen , pharmacokinetics , pharmacology , oral administration , chemistry , gastroenterology , biology , ecology , paleontology
The aim of the current study was to investigate whether multiple oral dosing of valacyclovir could result in plasma concentrations exceeding the EC 50 ‐value of acyclovir against equine herpesvirus 1 (EHV1) during the majority of the treatment period. Additionally, we wanted to determine the concentration of acyclovir in nasal mucus and cerebrospinal fluid (CSF). Valacyclovir was administered to four horses and two ponies, three times daily, at a dosage of 40 mg/kg, for four consecutive days. Blood was collected prior to each administration and 1 h after dosing. Nasal mucus samples and CSF were collected once during treatment; 1 h after the last administration. This dosage regimen resulted in plasma concentrations that were higher than the EC 50 ‐value of 1.7 μg/mL, i.e. EC 50 of an isolate highly susceptible to acyclovir, for 80% of the treatment period; and higher than the EC 50 ‐value of 3.0 μg/mL, i.e. EC 50 of an isolate less susceptible to acyclovir, for 60% of the treatment period. Concentration in nasal mucus samples and CSF was 0.36–1.17 μg/mL and 0.11–0.23 μg/mL, respectively. This study illustrates that multiple dosing of valacyclovir may result in a therapeutic benefit as plasma concentrations could be maintained above the EC 50 ‐value of acyclovir against EHV1 for more than 50% of the treatment period. Acyclovir could be detected in both nasal mucus samples and CSF. However, these concentrations were lower than the EC 50 .