C H A P T E R 9
Antibiotics
103
KEY POINTS
■■
Cephalosporins are a large group of antibiotics,
similar to penicillin, that are effective against a wide
range of bacteria.
■■
Monitor for GI upsets and diarrhoea,
pseudomembranous colitis, headache, dizziness and
superinfections.
KEY POINTS
MACROLIDES
The macrolides (Table 9.9) are antibiotics that inter-
fere with protein synthesis in susceptible bacteria.
Macrolides include erythromycin (
Erythrocin
,
Eryc
and others), azithromycin (
Zithromax
), clarithromycin
(
Clarac, Kalixocin, Klacid
) and roxithromycin (
Rulide
).
Therapeutic actions and indications
The macrolides, which may be bactericidal or
bacteriostatic, exert their effect by binding to the bac-
terial cell membrane and changing protein function
(see Figure 9.1). This action can prevent the cell from
dividing or cause cell death, depending on the sensitivity
of the bacteria and the concentration of the drug.
Macrolides are indicated for treatment of the
following conditions: acute infections caused by suscep-
tible strains of
S. pneumoniae
,
M. pneumoniae
,
Listeria
monocytogenes
and
Legionella pneumophila
; infections
caused by group A betahaemolytic streptococci; pelvic
inflammatory disease caused by
N. gonorrhoeae
;
upper
respiratory tract infections caused by
H. influenzae
(with sulfonamides); infections caused by
Corynebacte-
rium diphtheriae
and
Corynebacterium minutissimum
(with antitoxin); intestinal amoebiasis; and infections
caused by
C. trachomatis.
See Table 9.9 for usual indi-
cations for each of these agents.
In addition, macrolides may be used as prophylaxis
for endocarditis before dental procedures in people
with valvular heart disease who are allergic to penicil-
lin. Topical macrolides are indicated for the treatment of
ocular infections caused by susceptible organisms and for
acne vulgaris, and they may also be used prophylactically
against infection in minor skin abrasions and for the treat-
ment of skin infections caused by sensitive organisms.
Pharmacokinetics
The macrolides are widely distributed throughout the
body; they cross the placenta and enter the breast milk
(see contraindications and cautions). These drugs are
absorbed in the GI tract.
Erythromycin is metabolised in the liver, with
excretion mainly in the bile to faeces. The half-life of
erythromycin is 1.6 hours.
Azithromycin and clarithromycin are mainly
excreted unchanged in the urine, making it necessary
to monitor renal function when people are taking these
drugs. The half-life of azithromycin is 68 hours, making
it useful for people who have trouble remembering to
take pills because it can be given once a day. The half-
life of clarithromycin is 3 to 7 hours.
Contraindications and cautions
Macrolides are contraindicated in people with known
allergy to any macrolide
because cross-sensitivity
■
■
Monitor injection sites regularly
to provide warm
compresses and gentle massage to injection sites
if they are painful or swollen.
If signs of phlebitis
occur, remove the IV line and reinsert in a different
vein.
■
■
Initiate safety measures, including adequate
lighting, side rails on the bed and assistance with
ambulation
to protect the person from injury if
CNS effects occur.
■
■
Instruct the person about the appropriate dosage
schedule and about possible side effects
to enhance
knowledge about drug therapy and to promote
compliance.
■
■
Provide the following teaching:
–– Take safety precautions, including 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.
–– Report difficulty breathing, severe headache,
severe diarrhoea, dizziness or weakness.
–– Avoid consuming alcoholic beverages while
receiving cephalosporins and for at least 72 hours
after completing the drug course because serious
side effects could occur.
Evaluation
■
■
Monitor person’s response to the drug (resolution
of bacterial infection).
■
■
Monitor for adverse effects (orientation and affect;
renal toxicity; hepatic dysfunction; GI effects; and
local irritation, including phlebitis at injection and
IV sites).
■
■
Evaluate effectiveness of the teaching plan (person
can name drug, dosage, possible adverse effects to
expect and specific measures to help avoid adverse
effects).
■
■
Monitor effectiveness of comfort and safety
measures and the person’s compliance with the
regimen.
