C H A P T E R 9
Antibiotics
97
KEY POINTS
■■
Aminoglycosides inhibit protein synthesis in
susceptible strains of gram-negative bacteria.
■■
These drugs are reserved for use in serious
infections because of potentially serious adverse
effects. Monitor for ototoxicity, renal toxicity,
GI disturbances, bone marrow depression and
superinfections.
CARBAPENEMS
The carbapenems (Table 9.2) are a relatively new
class of broad-spectrum antibiotics effective against
gram-positive and gram-negative bacteria. Meropenem,
the first drug of the class, was discussed in Chapter 8
and has limited use because of the severe risk for poten-
tially fatal GI toxicities. Newer carbapenems are not as
toxic. Carbapenems discussed here include doripenem
(
Doribax
), ertapenem (
Invanz
) and imipenem-cilastatin
(
Primaxin
).
Therapeutic actions and indications
The carbapenems are bactericidal. They inhibit cell
membrane synthesis in susceptible bacteria, leading to
cell death (Figure 9.2). These drugs are used to treat
serious infections caused by susceptible strains of
Streptococcus pneumoniae
,
Haemophilus influenzae
,
Moraxella catarrhalis
,
Staphylococcus aureus
,
Strepto-
coccus pyogenes
,
Escherichia coli
,
Peptostreptococcus
,
Klebsiella pneumoniae
,
Clostridium clostridioforme
,
Eubacterium lentum
,
Bacteroides fragilis
,
Bacteroides
distasonis
,
Bacteroides ovatus
,
Bacteroides thetaio-
tamicron
,
Bacteroides uniformis
,
Proteus mirabilis
,
Pseudomonas aeruginosa
,
Acinetobacter baumannii
,
Streptococcus agalactiae
,
Porphyromonas asaccharo-
lytica
,
Prevotella bivia
and other susceptible bacteria.
They are indicated for treating serious intra-abdominal,
urinary tract, skin and skin structure, bone and joint
and gynaecological infections. See Table 9.2 for usual
indications for each of these drugs.
Pharmacokinetics
These drugs are rapidly absorbed if given IM and reach
peak levels at the end of the infusion if given IV. They
are widely distributed throughout the body, although it
is not known whether they cross the placenta or enter
breast milk (see contraindications and cautions). Carb
apenems are excreted unchanged in the urine and have
an average half-life of 1 to 4 hours.
Doripenem is given IV every 8 hours by a 1-hour IV
infusion for 5 to 14 days.
Ertapenem can be given IV or IM. It is given once a
day for 5 to 14 days, depending on the infection.
KEY POINTS
■
■
Monitor the infection site and presenting signs
and symptoms (e.g. fever, lethargy) throughout
the course of drug therapy.
Failure of these signs
and symptoms to resolve may indicate the need to
reculture the site.
Arrange to continue drug therapy
for at least 2 days after all signs and symptoms
resolve
to decrease the development of resistant
strains of bacteria.
■
■
Monitor regularly for signs of nephrotoxicity,
neurotoxicity and bone marrow suppression
to
effectively arrange for discontinuation of drug
or decreased dose, as appropriate, if any of
these toxicities occurs.
Provide safety measures
to protect the person if CNS effects, such as
confusion, disorientation or numbness and
tingling, occur.
■
■
Provide small, frequent meals as tolerated; frequent
mouth care; and ice chips or sugarless lollies to
suck if stomatitis and sore mouth are problems
to
relieve discomfort.
■
■
Provide
adequate fluids to replace fluid lost with
diarrhoea
.
■
■
Ensure that person is hydrated at all times during
drug therapy
to minimise renal toxicity from drug
exposure.
■
■
Instruct the person about the appropriate dosage
regimen and possible adverse effects
to enhance
knowledge about drug therapy and to promote
compliance.
■
■
Provide the following teaching:
–– Take safety precautions, such as changing
position slowly and avoiding driving and
hazardous tasks, if CNS effects occur.
–– Try to drink a lot of fluids and to maintain
nutrition (very important) even though nausea,
vomiting and diarrhoea may occur.
–– Avoid exposure to other infections (e.g. crowded
areas, people with known infectious diseases).
–– Report difficulty breathing, severe headache, loss
of hearing or ringing in the ears, or changes in
urine output.
Evaluation
■
■
Monitor response to the drug (resolution of
bacterial infection).
■
■
Monitor for adverse effects (orientation and affect,
hearing changes, bone marrow suppression, renal
toxicity, hepatic dysfunction, GI effects).
■
■
Evaluate effectiveness of the teaching plan (person
can name drug, dosage, possible adverse effects
to watch for and specific measures to help avoid
adverse effects).
■
■
Monitor effectiveness of comfort and safety
measures and compliance with the therapeutic
regimen.
