Antivirals:
DEFINITION:
Antivirals are medications that directly attack VIRUSES. They are not
ANTIBIOTICS, which attack BACTERIA. Antivirals are also much newer than antibiotics. Until recently,
antivirals were mainly used against severe life-threatening viral conditions. However, modern antivirals
exist against FLU, GENITAL HERPES, HIV, VIRAL HEPATITIS, and other VIRAL CONDITIONS.
DESCRIPTION:
Antiviral drugs are medicines that cure or control virus infections. Exclusive of the antiretroviral agents
used in HIV (AIDS) therapy, there are currently only 11 antiviral drugs available, covering four types of
virus. Acyclovir (Zovirax), famciclovir (Famvir), and valacyclovir (Valtrex) are effective against
herpesvirus, including herpes zoster and herpes genitalis. They may also be of value in either conditions
caused by herpes, such as CHICKENPOX and SHINGLES. These drugs are not curative, but may
reduce the pain of a herpes outbreak and shorten the period of viral shedding.Amantadine (Symmetrel),
oseltamivir (Tamiflu), rimantidine (Flumadine), and zanamivir (Relenza) are useful in treatment of
INFLUENZA virus. Amantadine, rimantadine, and oseltamivir may be administered throughout the flu
season as preventatives for patients who cannot take influenza virus vaccine.Cidofovir (Vistide), foscarnet
(Foscavir), and ganciclovir (Cytovene) have been beneficial in treatment of cytomegalovirus in
immunosupressed patients, primarily HIV-positive patients and transplant recipients. Ribavirin (Virazole)
is used to treat respiratory syncytial virus. In combination with interferons, ribavirin has shown some
efficacy against HEPATITIS C, and there have been anecdotal reports of utility against other types of viral
infections.As a class, the antivirals are not curative, and must be used either prophylactically or early in
the development of an infection. Their mechanism of action is typically to inactivate the enzymes needed
for viral replication. This will reduce the rate of viral growth, but will not inactive the virus already present.
Antiviral therapy must normally be initiated within 48 hours of the onset of an infection to provide any
benefit. Drugs used for influenza may be used throughout the influenza season in high risk patients, or
within 48 hours of exposure to a known carrier. Antiherpetic agents should be used at the first signs of an
outbreak. Anti-cytomegaloviral drugs must routinely be used as part of a program of secondary
prophylaxis (maintenance therapy following an initial response) in order to prevent reinfection in
immunocompromised patients.
INDICATIONS:
any of the conditions for which a particular drug treatment may be
Prescribed.
SHINGGLES:
Shingles: Introduction
Herpes zoster is an infectious viral infection that is believed to
be caused by the re-activation of a previous chickenpox infection, often
from many years before. Shingles is a painful condition characterized by
the appearance of a skin rash. When the immune system of the body
becomes weak the virus may get reactivated and this can result in
appearance of shingles symptoms.
Any individual who has suffered from chicken pox can develop
shingles. However the shingles symptoms are most often seen in
individuals who are around 60 years old.
Causes of Shingles:
FOLLOWING IS A LIST OF CAUSES OR UNDERLYING
CONDITIONS THAT COULD POSSIBLY CAUSE SHINGLES.
* VARICELLA-ZOSTER VIRUS
This condition is caused by the VARICELLA-ZOSTER VIRUS, and this virus also causes chicken pox disease.
In fact once a person has had the chicken pox this virus remains within the body in a dormant or latent
condition. When the immune system of the body becomes weak the virus may get reactivated and this
can result in appearance of shingles symptoms.
Symptoms of Shingles:
The shingles symptoms begin with increased sensitivity of skin along with a burning
pain. Some patients may also experience tickling or tingling along with numbness in the areas. In such a
stage it is often difficult to determine the reason for the pain. The areas that are typically affected
include the head, abdomen, neck, face and arm or leg. In rare cases areas of the face like the nose and
eyes may also be affected. Along with tingling of skin patients also tend to experience other problems
like stomach ache, chills, diarrhea along with fe
Treatments for Shingles:
The list of treatments mentioned in various sources for Shingles includes the following
list:
ZIVORAX is the brand name for acyclovir, a synthetic nucleoside
analogue active against herpesviruses. ZOVIRAX Capsules, Tablets, and
Suspension are formulations for oral administration. Each capsule of
ZOVIRAX contains 200 mg of acyclovir and the inactive ingredients corn
starch, lactose, magnesium stearate, and sodium lauryl sulfate. The
capsule shell consists of gelatin, FD&C Blue No. 2, and titanium dioxide.
May contain one or more parabens. Printed with edible black ink.
Each 800-mg tablet of ZOVIRAX contains 800 mg of acyclovir and each 400-mg tablet of ZOVIRAX
contains 400 mg of acyclovir.
Acyclovir is a white, crystalline powder with the molecular formula C8H11N5O3 and a molecular
weight of 225. The maximum solubility in water at 37°C is 2.5 mg/mL. The pka's of acyclovir
are 2.27 and 9.25.
The chemical name of acyclovir is 2-amino-1,9-dihydro-9-[(2-hydroxyethoxy)methyl]-6H-purin6-one; it has the following structural formula:
VALCYCLOVIR
FAMCICLOVIR
Valacyclovir hydrochloride is rapidly converted to acyclovir
which has demonstrated antiviral activity against herpes simplex virus
types 1 ( HSV-1 ) and 2 ( HSV- 2 ) and varicella-zoster virus ( VZV ) both
in vitro and in vivo. In cell culture, acyclovirُ s highest antiviral activity is
against HSV-1, followed in decreasing order of potency against HSV-2
and VZV.
The inhibitory activity of acyclovir is highly selective due to its affinity
for the enzyme thymidine kinase (TK) encoded by HSV, VZV , and EBV.
This is accomplished in three ways: 1) competitive inhibition of viral
DNA polymerase,2) incorporation and termination of the growing viral
Disease.
Famvir is an oral antiviral prescription medication used to treat
certain viral infections caused by herpes viruses include genital herpes,
cold sores, shingles, and chicken pox, symptoms of herpes zoster (also
known as shingles), a herpes virus infection of the skin and suppress
recurrent episodes of genital herpes infection of the mucous
membranes (lips and mouth) and genitals in HIV-infected patients.
Although famciclovir will not cure genital herpes or herpes zoster, it
does help relieve the pain and discomfort and helps the sores heal
faster. Famvir is the first and only herpes medicine proven to stop or
shorten a recurrent genital herpes outbreak with just a single day of
treatment.
Famvir slows the growth and spread of the herpes virus so that the body can fight off the infection.
Famciclovir is not a cure for the infections, but treating an outbreak can speed up healing of the sores,
decrease pain, and lower the risk of complications from the virus (e.g., whole body infection, brain
infection, persistent pain after sore healing). Famciclovir is used in the treatment of some of the various
forms of the herpes virus as well as the virus responsible for causing the symptoms of shingles.
Treatment with Famvir should be started as soon as possible after the first appearance of symptoms
(such as tingling, burning, blisters). Take this medication by mouth with or without food, usually 2-3
times daily. Famvir is most effective if started within the first 48 hours after shingles first appears,
treatment should be started at the first sign or symptom of genital herpes. Famvir treatment may not be
effective if it is delayed more than 72 hours after the herpes zoster rash first appears or more than 6
hours after genital herpes becomes evident.