106
P A R T 2
Chemotherapeutic agents
KEY POINTS
■■
Lincosamides are similar to macrolides but are
more toxic. They are used to treat severe infections.
Monitor the person for pseudomembranous colitis,
bone marrow depression, pain and CNS effects.
■■
Macrolides are in a class of older antibiotics that
can be bactericidal or bacteriostatic. They are used
to treat URTIs and UTIs, and are often used when
people are allergic to penicillin. Monitor the person
for nausea, vomiting, diarrhoea, dizziness and other
CNS effects.
■■
The monobactam antibiotic aztreonam is effective
against only gram-negative enterobacteria; it is
safely used when people are allergic to penicillin
or cephalosporins. Monitor the person taking
aztreonam for GI problems, liver toxicity and pain
at the injection site.
FLUOROQUINOLONES
The fluoroquinolones (Table 9.4) are a relatively new
synthetic class of antibiotics with a broad spectrum
of activity. Fluoroquinolones include ciprofloxa-
cin (
Ciproxin, Ciprol
), which is the most widely used
fluoroquinolone; moxifloxacin (
Avelox
), norfloxacin
(
Noroxin, Nufloxib
) and ofloxacin (
Ocuflox
).
Therapeutic actions and indications
The fluoroquinolones enter the bacterial cell by passive
diffusion through channels in the cell membrane. Once
inside, they interfere with the action of DNA enzymes
necessary for the growth and reproduction of the
bacteria (see Figure 9.1). This leads to cell death because
the bacterial DNA is damaged and the cell cannot be
maintained. The fluoroquinolones have the advantage
of a unique way of disrupting bacterial activity. There
KEY POINTS
is little cross-resistance with other forms of antibiotics.
However, misuse of these drugs in the short time the
class has been available has led to the existence of
resistant strains of bacteria (see contraindications and
cautions).
The fluoroquinolones are indicated for treating
infections caused by susceptible strains of gram-negative
bacteria, including
E. coli
,
P. mirabilis
,
K. pneumoniae
,
Enterobacter cloacae
,
Proteus vulgaris
,
Proteus rettgeri
,
Morganella morganii
,
Moraxella catarrhalis
,
H. influ-
enzae
,
H. parainfluenzae
,
P. aeruginosa
,
Citrobacter
freundii
,
S. aureus
,
Staphylococcus epidermidis
, some
Neisseria gonorrhoeae
and group D streptococci. These
infections frequently include urinary tract, respiratory
tract and skin infections. Ciprofloxacin is effective
against a wide spectrum of gram-negative bacteria. In
2001, it was approved for prevention of anthrax infec-
tion in areas that might be exposed to germ warfare. It
is also effective against typhoid fever. See Table 9.4 for
usual indications for each of these agents.
Pharmacokinetics
The fluoroquinolones are absorbed from the GI tract,
metabolised in the liver and excreted in the urine and
faeces. These drugs are widely distributed in the body
and cross the placenta and enter breast milk (see contra
indications and cautions).
Ciprofloxacin is available in injectable, oral and
topical forms. Moxifloxacin is available in oral and IV
forms. Norfloxacin is only available in an oral form.
Ofloxacin is available as an ophthalmic agent for the
treatment of ocular infections caused by susceptible
bacteria.
Contraindications and cautions
Fluoroquinolones are contraindicated in people with
known allergy to any fluoroquinolone and in pregnant
or breastfeeding women
because potential effects on
the fetus and infant are not known.
Use with caution
in the presence of renal dysfunction,
which could inter-
fere with the metabolism and excretion of the drug
,
and seizures,
which could be exacerbated by the drugs’
effects on cell membrane channels.
Because so many resistant strains are emerging,
always perform culture and sensitivity tests of infected
tissue
to determine the exact bacterial cause and sensi-
tivity.
These drugs have been associated with lesions in
developing cartilage and therefore are not recommended
for use in children younger than 18 years of age.
Adverse effects
These drugs are associated with relatively mild adverse
reactions. The most common are headache, dizziness,
insomnia and depression related to possible effects
–– Report difficulty breathing, severe headache,
severe diarrhoea, severe skin rash, and mouth or
vaginal sores.
Evaluation
■
■
Monitor person’s response to the drug (resolution
of bacterial infection).
■
■
Monitor for adverse effects (orientation and affect,
GI effects, superinfections).
■
■
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.
