Chapter 40: Antivirals pg650 Flashcards
Viruses can enter the body through at least four routes:
inhalation
through the respiratory tract, ingestion via the gastrointestinal
(GI) tract, transplacentally via mother to infant, and
inoculation via skin or mucous membranes.
changes in the cell associated
with viral replication are known as the
cytopathic effect and
usually result in the destruction of the host cell.
Drugs that actually destroy virions include
disinfectants and immunoglobulins. Disinfectants such
as povidone-iodine (Betadine) are virucides and are commonly
used to disinfect medical equipment
Many drugs for the treatment of HIV are approved by the
U.S. Food and Drug Administration (FDA) via an
accelerated
process, which means that they are approved faster than other
drugs, because of the nature of the illness.
All virions contain a genome that consists
of either DNA or RNA
antiviral
drugs interfere with viral nucleic acid synthesis. Other antiviral
drugs work by preventing the fusion process
opportunistic
infections
infections caused by organisms
that would not normally harm an immunocompetent person
Most antiviral drugs
are
synthetic purine or pyrimidine nucleoside or nucleotide
analogues
Antiretroviral drugs
are indicated specifically for
the treatment of infections caused by HIV, the virus that causes
AIDS.
Herpes simplex virus type 1 HSV 1
causes mucocutaneous herpes—usually in the form of perioral
blisters (“fever blisters” or “cold sores”).
Herpes simplex
virus type 2 (HSV-2)
causes genital herpes
Human herpesvirus
3 (HHV-3)
causes both chickenpox and shingles. This virus is
more commonly known as herpes zoster virus or varicella-zoster
virus (VZV)
Human herpesvirus 4 (HHV-4),
known as Epstein-Barr virus, is associated with illnesses such
as infectious mononucleosis (“mono”) and chronic fatigue
syndrome.
Human herpesvirus 5 (HHV-5)
known as cytomegalovirus (CMV) and is the cause of CMV retinitis
(a serious viral infection of the eye) and CMV disease, which
is most commonly seen in immunocompromised patients
Human herpesvirus
8
known as Kaposi’s sarcoma herpesvirus, is an oncogenic
(cancer-inducing) virus believed to cause Kaposi’s sarcoma, an
AIDS-associated cancer
Chickenpox, highly contagious
spread by either direct contact with weeping lesions or via
droplet inhalation
Zoster lesions are
often quite painful
opioids for
pain control. In addition, postherpetic neuralgias (long-term
nerve pain) remain following shingles outbreaks in up to 50%
of elderly patients
vaccines…
varicella virus vaccine was approved in 1995, older than 1 yr old, never had chicken pox
Zostavax, is available for prevention of herpes shingles in
patients 50 years of age or older
Because viruses reproduce in human cells
selective killing is
difficult
healthy human cells, in addition
to virally infected cells, may be killed in the process, which
results in more serious toxicities for these drugs
Amantadine (Symmetrel) narrow antiviral spectrum…
influenza A viruses
rimantadine
Valacyclovir is a
prodrug that is metabolized to acyclovir
in the body
greater oral bioavailability
A common
site of CMV infections in the immunocompromised patient
the eye, and it can result in CMV retinitis, a devastating viral
infection that can lead to blindness
Ganciclovir
The dose-limiting toxicity of ganciclovir treatment
is bone
marrow suppression, whereas that of foscarnet and cidofovir
is renal toxicity.
For example, a heart transplant recipient who contracts CMV
retinitis is immunocompromised because of immunosuppressant
drug therapy and is most likely taking cyclosporine
which
is nephrotoxic. Therefore, using foscarnet in this patient may
be more dangerous than using ganciclovir
a patient who contracts a CMV infection and is immunocompromised
because of a bone marrow transplant might be better
treated using
fosarnet
Ribavirin (Virazole) is a synthetic nucleoside analogue of guanosine
It interferes with both RNA
and DNA synthesis and as a result inhibits both protein synthesis
and viral replication overall.
stages of HIV
The most recent WHO model
lists four stages as follows:
- Stage 1: asymptomatic infection
- Stage 2: early, general symptoms of disease
- Stage 3: moderate symptoms
- Stage 4: severe symptoms, often leading to death
CD4 refers to the
protein on the cell surface of helper
T lymphocytes, to which HIV virions attach themselves
(HAART) refers to
Highly active antiretroviral therapy combinations of antiretroviral drugs (“cocktails”) that are now standard for treating HIV-infected patients.
Zidovudine (Retrovir), also known as azidothymidine or AZT
is given to HIV-infected pregnant
women and even to newborn babies to prevent maternal transmission
of the virus to the infant
Ribavirin
is contraindicated
in pregnant women and in their male
sexual partners due to its teratogenic properties; it must also
not be handled by health care personnel who are or might
be pregnant
Ganciclovir is associated
with bone marrow
suppression; therefore, assess blood counts prior to and
during use.
With use of HIV antivirals or antiretrovirals,
Bone demineralization is yet another adverse effect
with long-term use, so assessment of calcium and vitamin
D levels is crucial
Instruct the patient to take oral antivirals
with meals to help
minimize GI upset. Also advise the patient to store capsules at
room temperature and not to crush or break the capsules
Amantadine and other antivirals need to be taken for the
entire course of therapy, and, if a dose is missed, instruct the
patient to take the dose as soon as it is remembered or contact
the prescriber for further instructions
How is the effectiveness of antiviral drugs administered to treat HIV infection assessed and evaluated?
All antiretroviral drugs work to reduce the viral load, which is the number of viral RNA copies per milliliter of blood.
Viruses can enter the body through at least four routes:
inhalation through the respiratory tract, ingestion via the GI tract, transplacentally via mother to infant, and inoculation via skin or mucous membranes. The inoculation route can take several forms, including sexual contact, blood transfusions, sharing of syringes or needles, organ transplantation, and animal bites (including human, animal, insect, spider, and others).
