C H A P T E R 9
Antibiotics
121
KEY POINTS
■■
The mycobacteria have an outer coat of mycolic
acid that protects them from many disinfectants
and allows them to survive for long periods in the
environment. These slow-growing bacteria may need
to be treated for several years before they can be
eradicated. They cause tuberculosis and leprosy.
■■
Antituberculosis drugs are used in combination to
increase effectiveness and decrease the emergence of
resistant strains. These drugs are divided into first-
line and second-line drugs. Adverse effects include
rashes, an orange tint to body fluids and GI reactions.
■■
Dapsone is the only antibiotic now used on its own to
treat leprosy. Thalidomide was recently reintroduced
to treat an unusual reaction many people develop
after being on dapsone.
KEY POINTS
NEW CLASSES OF ANTIBIOTICS AND
ADJUNCTS
Research is constantly being done to develop new
antibiotics to affect the emerging resistant strains of
bacteria. New classes of antibiotics are daptomycin
(
Cubicin
), linezolid (
Zyvox
) and tigecycline (
Tygacil
)
.
See the following for additional information about each
of these agents.
Adjuncts to antibiotic therapy include clavulanic
acid and thalidomide (see Box 9.6).
Daptomycin was introduced in 2003 as a cyclic
lipopeptide antibiotic. This class of drug binds to bac-
terial cell membranes, causing a rapid depolarisation of
membrane potential. The loss of membrane potential
leads to the inhibition of protein and DNA and RNA
synthesis, which results in bacterial cell death. Dapto-
mycin is approved for treating complicated skin and skin
structure infections caused by susceptible gram-posi-
tive bacteria, including MRSA
.
It must be given IV over
30 minutes, once each day for 7 to 14 days, which makes
its use inconvenient. People should be monitored for
pseudomembranous colitis and myopathies.
Linezolid (
Zyvox
) was introduced in 2000. This
drug is indicated specifically for treatment of infections
caused by vancomycin-resistant and methicillin-resistant
strains of bacteria. It is available in intravenous and oral
forms. The usual adult dosage is 600 mg PO, or it may
be administered IV q 12 hours for 10 to 14 days. This
drug must also be used cautiously and only when a sen-
sitive bacterial species has been clearly identified. It is
the first oral drug approved for the treatment of diabetic
foot ulcers. These drugs are part of a wide variety of
compounds that are being investigated to deal with the
increasing problem of resistant bacteria.
Tigecycline (
Tygacil
) was the first drug of a new
class of antibiotics called glycylcyclines. This antibiotic
inhibits protein translation on ribosomes of certain
bacteria, leading to their inability to maintain their
integrity and culminating in the death of the bacterium.
It is used in the treatment of complicated skin and skin
structure infections and intra-abdominal infections
caused by susceptible bacteria. Caution should be used
with a known allergy to tetracycline antibiotics because
a cross-sensitivity may occur. Women should be advised
to use a barrier form of contraceptive when on this
drug. People should be monitored for pseudomembra-
nous colitis, rash and superinfections.
Tygacil
is given
as 100 mg IV followed by 50 mg IV every 12 hours,
infused over 30 to 60 minutes for 5 to 14 days.
■
■
Provide the following teaching:
–– Try to drink a lot of fluids to maintain nutrition
(very important) even though nausea, vomiting
and diarrhoea may occur.
–– Use barrier contraceptives and understand
that oral contraceptives may not be effective if
antimycobacterials are being used.
–– Understand that normally some of these drugs
impart an orange stain to body fluids. If this
occurs, the fluids may stain clothing and tears
may stain contact lenses.
–– Report difficulty breathing, hallucinations,
numbness and tingling, worsening of condition,
fever and chills or changes in colour of urine or
stool.
Evaluation
■
■
Monitor person’s response to the drug (resolution
of mycobacterial infection).
■
■
Monitor for adverse effects (GI effects, CNS
changes and hypersensitivity reactions).
■
■
Evaluate the effectiveness of the teaching plan
(person can name the drug, dosage, possible
adverse effects to expect and specific measures
to help avoid adverse effects).
■
■
Monitor the effectiveness of comfort and safety
measures and compliance with the regimen.
