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DRUGS & SUPPLEMENTS
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PHL-Valacyclovir
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PHL-Valacyclovir uses
Pharmacological action
PHL-Valacyclovir is an antiviral agent of nucleosides group. Valacyclovir is the L-valine ester of acyclovir being thus a prodrug.
After absorption into the blood valacyclovir almost completely converted to acyclovir under the influence of hepatic enzyme valacyclovir-hydrolase. In turn Acyclovir formed from valacyclovir affected by the virus penetrates cells where under the influence of the viral enzyme thymidine kinase converted into a monophosphate, then under the influence of cellular kinases - in the active diphosphate and triphosphate. Acyclovir triphosphate inhibits DNA polymerase and thus violates the replication of virus DNA. In addition the violation of the replication of viral DNA may be a result of incorporation of acyclovir into its structure. Thus the high selectivity of valacyclovir for tissues infected with a virus, because the stage I reaction chain phosphorylation mediated by the enzyme produced by the virus.
This drug is active against Herpes Simplex virus types 1 and 2, Varicella Zoster, cytomegalovirus, Epstein-Barr virus, human herpes virus 6.
Pharmacokinetics
After oral administration PHL-Valacyclovir is well absorbed from the gastrointestinal tract rapidly and almost completely converted to acyclovir and L-valine by the enzyme valacyclovir-hydrolase.
After a single dose of 0.25-2 g of valacyclovir Cmax of acyclovir in healthy volunteers with normal renal function is an average of 10-37 mmol (2.2-8.3 mg / ml) and achieved in 1-2 hours.
Bioavailability of acyclovir when receiving from 1 g of valaciclovir is 54% and is independent of ingestion.
Cmax of valaciclovir in plasma is only 4% of the acyclovir and achieved an average of 30-100 minutes after ingestion, after 3 h Cmax level remains unchanged or declines.
Binding of valaciclovir to plasma proteins is very low - 15%.
Why is PHL-Valacyclovir prescribed?
PHL-Valacyclovir is used for the treatment and prevention of infectious diseases caused by Herpes Zoster.
Prevention of cytomegalovirus infection developing in organ transplantation.
Dosage and administration
For oral administration a single PHL-Valacyclovir dose for adults is 0.25-2 g. Frequency of admission and length of treatment depend on the evidence.
For patients with severely impaired renal function requires correction dosing regimen.
PHL-Valacyclovir side effects, adverse reactions
Digestive system: nausea, discomfort, abdominal pain, vomiting, diarrhea, anorexia; rare - transient increase of indicators of liver samples.
CNS: headache, fatigue, dizziness, confusion, hallucinations; rare - impaired consciousness, in some cases - coma.
Allergic reactions: rarely - rash, urticaria, pruritus, angioedema, anaphylaxis.
Other: rarely - thrombocytopenia, dyspnea, renal dysfunction, photosensitivity.
PHL-Valacyclovir contraindications
Hypersensitivity to valacyclovir (valaciclovir), acyclovir.
Using during pregnancy and breastfeeding
There are no adequate and well-controlled studies safety of valaciclovir in pregnancy and lactation. Prescription of PHL-Valacyclovir for this category of patients is possible in cases where the expected benefits of therapy to the mother outweighs the potential risk to the fetus or infant. It is known that acyclovir is excreted in breast milk at concentrations of 0.6-4.1 times higher than its concentration in plasma. T1/2 of acyclovir in breast milk is 2.8 h, comparable to the T1/2 from blood plasma.
In experimental studies, valacyclovir had no teratogenic effects in rats and rabbits. For oral administration valacyclovir did not cause impaired fertility in male and female rats.
Special instructions
It is necessary to increase fluid intake for elderly patients during treatment.
Patients with kidney failure have an increased risk of neurological complications while taking PHL-Valacyclovir.
This drug used with caution in patients with liver disease.
Clinical experience in children is missing.
PHL-Valacyclovir drug interactions
Clinically significant drug interactions valacyclovir with other drugs is not established.
Acyclovir comes as unchanged in the urine through active tubular secretion. Any drugs prescribed with it at the same time and compete for the mechanism of elimination, can cause high concentrations of valaciclovir in plasma. Cimetidine and drugs that block tubular secretion in the appointment after receiving valacyclovir at a dose of 1 g of acyclovir enhance AUC rate and decrease its renal clearance.
Simultaneous administration of acyclovir with the inactive metabolite of mycophenolate mofetil observed an increase in AUC of acyclovir and mycophenolate mofetil.
Simultaneous administration of PHL-Valacyclovir with drugs violating renal function (including cyclosporine, tacrolimus) possibly worsening renal function.
PHL-Valacyclovir in case of emergency / overdose
Symptoms: sedimentation of acyclovir in renal tubules.
Treatment: dialysis (when acute renal failure and anuria).
PHL-Valacyclovir pharmaceutical active ingredients containing related brand and generic drugs:
PHL-Valacyclovir available forms, composition, doses:
Composition is the list of ingredients which combinedly form a medicine. Both active ingredients and inactive ingredients form the composition. The active ingredient gives the desired therapeutic effect whereas the inactive ingredient helps in making the medicine stable.
Doses are various strengths of the medicine like 10mg, 20mg, 30mg and so on. Each medicine comes in various doses which is decided by the manufacturer, that is, pharmaceutical company. The dose is decided on the severity of the symptom or disease.