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Antiretroviral drugs are medications
for the treatment of infection by
retroviruses, primarily HIV. When
several such drugs, typically three or
four, are taken in combination, the
approach is known as highly active
antiretroviral therapy.
The American National Institutes of
Health and other organizations recommend
offering antiretroviral treatment to all
patients with AIDS. Because of the
complexity of selecting and following a
regimen, the severity of the
side-effects and the importance of
compliance to prevent viral resistance.
What is antiretroviral drug
treatment?
This is the main type of treatment for
HIV or AIDS. It is not a cure, but it
can stop people from becoming ill for
many years. The treatment consists of
drugs that have to be taken every day
for the rest of a person’s life.
The aim of antiretroviral treatment is
to keep the amount of HIV in the body at
a low level. This stops any weakening of
the immune system and allows it to
recover from any damage that HIV might
have caused already.
The drugs are often referred to as:
* Antiretrovirals
* Anti-HIV or anti-AIDS drugs
* HIV antiviral drugs
* ARVs
The life cycle of HIV can be as short
as about 1.5 days from viral entry into
a cell, through replication,
assembly, and release of additional
viruses, to infection of other cells HIV
lacks proofreading enzymes to correct
errors made when it converts its RNA
into DNA via reverse transcription. Its
short life-cycle and high error rate
cause the virus to mutate very rapidly,
resulting in a high genetic variability
of HIV. Most of the mutations either are
inferior to the parent virus (often
lacking the ability to reproduce at all)
or convey no advantage, but some of them
have a natural selection superiority to
their parent and can enable them to slip
past defenses such as the human immune
system and antiretroviral drugs. The
more active copies of the virus the
greater the possibility that one
resistant to antiretroviral drugs will
be made, so antiretroviral combination
therapy defends against resistance by
suppressing HIV replication as much as
possible.
Combinations of antiretrovirals create
multiple obstacles to HIV replication to
keep the number of offspring low and
reduce the possibility of a superior
mutation. If a mutation that conveys
resistance to one of the drugs being
taken arises, the other drugs continue
to suppress reproduction of that
mutation. With rare exceptions, no
individual antiretroviral drug has been
demonstrated to suppress an HIV
infection for long; these agents must be
taken in combinations in order to have a
lasting effect. As a result, the
standard of care is to use combinations
of antiretroviral drugs. Combinations
usually comprise two nucleoside-analogue
RTIs and one non-nucleoside-analogue RTI
or protease inhibitor.This three drug
combination is commonly known as a
triple cocktail.
Combinations of antiretrovirals are
subject to positive and negative
synergies, which limits the number of
useful combinations. For example,
Didanosine and AZT inhibit each other,
so taking them together is less
effective than taking either one
separately. Other issues further limit
some people's treatment options from
antiretroviral drug combinations,
including their complicated dosing
schedules and often severe side-effects.
In recent years, drug companies have
worked together to combine these complex
regimens into simpler formulas, termed
fixed-dose combinations. For instance,
two pills containing two or three
medications each can be taken twice
daily. This greatly increases the ease
with which they can be taken, which in
turn increases adherence, and thus their
effectiveness over the long-term. Lack
of adherence is a primary cause of
resistance development in
medication-experienced patients.
Patients able to adhere at this rate and
higher can maintain one regimen for up
to a decade without developing
resistance. This greatly increases
chances of long-term survival, as it
leaves more drugs available to the
patient for longer periods of time. |
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