144
P A R T 2
Chemotherapeutic agents
KEY POINTS
■■
The HIV virus infects helper T cells, leading to a
loss of immune function and the development of
opportunistic infections.
■■
Drugs used to treat HIV are usually given in
combination to affect the virus at various points
in the body: non-nucleoside and nucleoside reverse
transcriptase inhibitors block RNA and DNA activity
in the cell; protease inhibitors prevent maturation
of the virus; fusion inhibitors prevent the entry of
the virus into the cell; CCR5 coreceptor antagonists
prevent the virus from reacting with the receptor on
the cell membrane, preventing its entry into the cell;
and integrase inhibitors block an enzyme essential for
formation of the provirus within the cell, leading to
decrease in the number of viruses.
■■
People taking drugs to treat HIV need to take all of
the medications continuously as prescribed and take
precautions to prevent the spread of the disease to
others.
ANTI-HEPATITIS B AND C AGENTS
Hepatitis B
and C are serious-to-potentially fatal viral
infections of the liver. The hepatitis B and C virus can
be spread by blood or blood products, sexual contact
or contaminated needles or instruments. Healthcare
workers are at especially high risk for contracting hepa-
titis infection due to needle stick injuries. Hepatitis B has
a higher mortality than other types of hepatitis. Individ-
uals infected may also develop a chronic condition or
KEY POINTS
become a carrier. In the past, hepatitis B and C were
treated with interferons (see Chapter 17). In 2004 and
2005, adefovir (
Hepsera
) and entecavir (
Baraclude
) were
approved specifically for treating chronic hepatitis B.
In 2006, another nucleoside reverse transcriptase inhib-
itor, telbivudine (
Sebivo
), was found to be very effective
in preventing viral replication in people with active
hepatitis B. More recently, two drugs specifically for
hepatitis C, boceprevir (
Victrelis
) and telaprevir (
Incivo
)
have become available.
Therapeutic actions and indications
Adefovir, entecavir and telbivudine are indicated for the
treatment of adults with chronic hepatitis B who have
evidence of active viral replication and either evidence
of persistent elevations in serum aminotransferases or
histologically active disease. The drugs inhibit reverse
transcriptase in the hepatitis B virus and cause DNA
chain termination, leading to blocked viral replication
and decreased viral load (see Table 10.4). Boceprevir and
telaprevir block the HCV NS3 serine protease essential
for replication of the hepatitis C virus.
Pharmacokinetics
These drugs are rapidly absorbed from the GI tract, with
peak effects occurring in 0.5 to 1.5 hours (entecavir),
0.5 to 4 hours (adefovir) and 1 to 4 hours (telbivudine).
Entecavir and adefovir are metabolised in the liver and
excreted in the urine. Telbivudine is excreted unchanged
in the urine. Adefovir has a half-life of 7.5 hours; ente-
cavir has a half-life of 128 to 149 hours; and telbivudine
has a half-life of 40 to 49 hours. It is not known whether
to stop the replication of HIV, to control AIDS and to
maintain the functioning of your immune system.
A schedule will be plotted out to show exactly when to
take each of the drugs. It is very important that you take
all of the drugs and that you adhere to this schedule to
ensure that the drugs can be effective and reduce the
development of resistant strains of the virus.
These drugs are not a cure for HIV, AIDS or ARC.
Opportunistic infections may occur and regular medical
follow-up should be sought to deal with the disease.
These drugs do not reduce the risk of transmission of
HIV to others by sexual contact or by blood contamination;
use appropriate precautions.
Common effects of these drugs include the following:
•
Dizziness, weakness and loss of feeling:
Change positions
slowly. If you feel drowsy, avoid driving and dangerous
activities.
•
Headache, fever, muscle aches:
Analgesics may be ordered
to alleviate this discomfort. Consult with your healthcare
provider.
•
Nausea, loss of appetite, change in taste:
Small, frequent
meals may help. It is important to try to maintain good
nutrition. Consult your healthcare provider if this becomes
a severe problem.
• Report any of the following to your healthcare provider:
excessive fatigue, lethargy, severe headache, difficulty
breathing or skin rash.
• Avoid over-the-counter medications and herbal therapies;
many of them interact with your drugs and may make
them ineffective. If you feel that you need one of these,
check with your healthcare provider first.
• Schedule regular medical evaluations, including
blood tests, which are needed to monitor the effects
of these drugs on your body and to adjust doses as
needed.
• Tell any doctor, nurse, or other healthcare provider that
you are taking these drugs.
• Keep these drugs and all medications out of the
reach of children. Do not share these drugs with other
people.
