Zovirax aciclovir (acyclovir) 200mg 25 tablets — Made in Poland — Free Delivery

Acyclovir is a synthetic analogue of a purine nucleoside with high inhibitory activity in vitro and in vivo against herpes viruses, including herpes simplex virus types 1 and 2, varicella zoster virus, Epstein-barr virus and cytomegalovirus. in cell culture, acyclovir is most active against herpes simplex virus type 1, less active against herpes simplex virus type 2, varicella zoster virus, epstein-barr virus and cytomegalovirus. the antiviral activity of acyclovir is highly selective. the inhibitory activity of acyclovir against these viruses is highly selective. the enzyme thymidine kinase in a normal uninfected cell does not use acyclovir as a substrate, therefore toxicity to the host cells is minimal. nevertheless, thymidine kinase, encoded in herpes simplex viruses, varicella zoster virus, herpes zoster virus and Epstein-barr virus, converts acyclovir to acyclovir monophosphate, a nucleoside analogue, which is then sequentially converted to diphosphate and triphosphate using cell enzymes. after incorporation into the viral DNA of acyclovir, triphosphate interacts with viral DNA polymerase and disrupts viral DNA replication.

With prolonged or repeated courses of treatment of seriously ill patients with reduced immunity, cases of resistance of certain viral strains to acyclovir are possible. Most clinical cases of resistance are associated with viral thymidine kinase deficiency, but there are reports of damage to thymidine kinase and DNA. In vitro interactions of certain herpes simplex viruses with acyclovir can also lead to the formation of less sensitive strains. The relationship between the sensitivity of individual herpes simplex viruses in vitro and the clinical results of treatment with acyclovir is not fully understood.

Pharmacokinetics. Acyclovir is only partially absorbed in the intestine. The average peak stable concentration (Cssmax) in blood plasma after applying a dose of 200 mg with a 4-hour interval is 3.1 μmol (0.7 μg / ml), respectively, Cssmin - 1.8 μmol (0.4 μg / ml) ... Cssmax after applying doses of 400 and 800 mg with a 4-hour interval are 5.3 μmol (1.2 μg / ml) and 8 μmol (1.8 μg / ml), equivalent to Cssmin - 2.7 μmol (0.6 μg / ml) and 4 μmol (0.9 μg / ml).

In adults, T½ with the on / in the introduction of acyclovir is about 2.9 hours. Most of the preparation is excreted unchanged by the kidneys. The renal clearance of acyclovir is significantly higher than the clearance of creatinine, which indicates that the excretion of the preparation by the kidneys is carried out not only by glomerular filtration, but also by tubular secretion.

9-carboxymethoxymethylguanine, the only important metabolite of acyclovir that can be detected in urine, accounts for about 10-15% of the dose. If acyclovir is administered 1 hour after taking 1 g of probenecid, T½ and AUC increase by 18 and 40%, respectively.

In patients with chronic renal failure, the average T½ is 19.5 hours. The average T½ of acyclovir during hemodialysis is 5.7 hours. The concentration of acyclovir in blood plasma during dialysis decreases by about 60%.

The CSF concentration is about 50% of the corresponding plasma concentration. The degree of binding to blood plasma proteins is relatively low (from 9 to 33%) and does not change when interacting with other preparations.

With the simultaneous use of acyclovir and zidovudine for the treatment of HIV-infected patients, no changes in the pharmacokinetics of these preparations have been revealed.