Pharmacokinetics of a single oral dose of acyclovir and valacyclovir in North American box turtles (Terrapenesp.)

Advances in Reptile Clinical Therapeutics

“…The elimination half-life was 8.9 Ϯ 3.8 hours, and the authors proposed that a higher milligram dose be administered every 12 to 24 hours. A recently published study 113 on the pharmacokinetics of acyclovir in North American box turtles (Terrapene carolina) after a single oral dose of 40 mg/kg valacyclovir (the esterified form that is rapidly converted to acyclovir after oral administration) found the elimination half-life to be 14.6 hours, and the C max of 1.94 μg/mL was reached 13.0 Ϯ 7 hours after administration. Prolonged lethargy was noted in 1 turtle after receiving the dose of valacyclovir.…”

“…Valacyclovir may also have some effect on iridoviruses, consequently further research is warranted. 113 Ganciclovir Ganciclovir is a synthetic guanine derivative that is active against human cytomegalovirus and herpesvirus. 118 Ganciclovirs mechanism of action is similar to acyclovir and has a solubility of 2.6 mg/mL in water at 251C (771F) and pKa values of 2.2 and 9.4.…”

“…Antiviral agents that have been evaluated in reptiles include acyclovir, ganciclovir, and valacyclovir. [112][113][114] Acyclovir Acyclovir is a synthetic purine nucleoside analogue that interferes with nucleic acid synthesis and is active against herpes viruses. 115 The inhibitory activity of acyclovir is highly selective because of an affinity for thymidine kinase encoded by herpes viruses, which phosphorylates acyclovir into a nucleotide analogue that is further converted by a series of enzymes into acyclovir triphosphate.…”

“…Acyclovir triphosphate stops replication of herpes virus DNA by competitive inhibition of viral DNA polymerase, incorporation into and termination of the growing DNA chain, and inactivation of viral DNA polymerase. 113,115 Acyclovir is available in tablets, capsules, oral suspension, and by injection. Acyclovir 0 s average bioavailability after oral administration in humans is 10% to 20%, and food does not affect absorption of the drug.…”

In vitro and in vivo assessment of eprociclovir as antiviral treatment against testudinid herpesvirus 3 in Hermann's tortoise (Testudo hermanni)

“…The half-life of EPV in tortoises is shorter than that of ACV in turtles (Terrapene carolina) (Allender et al, 2013). However, it is important to note that EPV is a nucleoside analogue which accumulates in the cytoplasm of cells after its conversion into a triphosphate active form (Jordheim et al, 2013).…”