C H A P T E R 9
Antibiotics
107
on the CNS membranes. GI effects include nausea,
vomiting, diarrhoea and dry mouth, related to direct
drug effect on the GI tract and possibly to stimulation of
the chemoreceptor trigger zone (CTZ) in the CNS.
Immunological effects include bone marrow depres-
sion, which may be related to drug effects on the cells
of the bone marrow that rapidly turn over. Other
adverse effects include fever, rash and photosensitivity,
a potentially serious adverse effect that can cause severe
skin reactions. Advise people to avoid sun and ultra
violet light exposure and to use protective clothing and
sunscreens.
Clinically important drug–drug interactions
When fluoroquinolones are taken concurrently with iron
salts, sucralfate, mineral supplements or antacids, the
therapeutic effect of the fluoroquinolone is decreased.
If this drug combination is necessary, administration of
the two agents should be separated by at least 4 hours.
If fluoroquinolones are taken with drugs that
increase the QTc interval or cause torsades de pointes
(quinidine, procainamide, amiodarone, sotalol, ery
thromycin, pentamidine, tricyclics, phenothiazines),
severe-to-fatal cardiac reactions are possible. These
combinations should be avoided, but if they must be
used, the person should be hospitalised with continual
cardiac monitoring.
Combining fluoroquinolones with theophylline
leads to increased theophylline levels because the
two drugs use similar metabolic pathways. The theo
phylline dose should be decreased by half and serum
theophylline levels monitored carefully. In addition,
when fluoroquinolones are combined with non-steroidal
anti-inflammatory drugs (NSAIDs), an increased risk of
CNS stimulation is possible. If this combination is used,
closely monitor the person, especially those who have a
history of seizures or CNS problems.
TABLE 9.4
DRUGS IN FOCUS Fluoroquinolones
Drug name
Dosage/route
Usual indications
ciprofloxacin (Ciproxin,
Ciprol)
Adult: 100–500 mg b.d. PO for up to 6 weeks;
reduce dose in renal failure
Paediatric: not recommended because of
potential effects on developing cartilage
Treatment of infections caused by a wide
spectrum of gram-negative bacteria
moxifloxacin (Avelox)
Adult: 400 mg/day PO or IV for 5–10 day;
reduce dose in renal impairment
Treatment of adults with sinusitis,
bronchitis, or community-acquired
pneumonia
norfloxacin (Noroxin,
Nufloxib)
Adult: 400 mg PO q 12 hours for up to 28 days;
reduce dose in renal impairment
Treatment of various urinary tract
infections
ofloxacin (Ocuflox)
Adult: 1–2 gutte into affected eye every
30 mins to q 6 hours
Treatment of corneal ulcers, bacterial
conjunctivitis
Prototype summary: Ciprofloxacin
Indications:
Treatment of respiratory,
dermatological, urinary tract, ear, eye, bone and
joint infections; treatment after anthrax exposure,
typhoid fever.
Actions:
Interferes with DNA replication in
susceptible gram-negative bacteria, preventing cell
reproduction.
Pharmacokinetics:
Route Onset
Peak
Duration
Oral
Varies
60–90 minutes 4–5 hours
IV 10 minutes 30 minutes
4–5 hours
T
1/2
:
3.5 to 4 hours; metabolised in the liver,
excreted in bile and urine.
Adverse effects:
Headache, dizziness, hypotension,
nausea, vomiting, diarrhoea, fever, rash.
Care considerations for
people receiving fluoroquinolones
Assessment: History and examination
■
■
Assess for
possible contraindications or cautions
:
known allergy to any fluoroquinolone (obtain
specific information about the nature and
occurrence of allergic reactions); history of renal
disease,
which could interfere with excretion of
the drug
; and current pregnancy or breastfeeding
status
because of potential adverse effects on the
fetus or infant.
■
■
Perform physical assessment
to establish baseline
data for assessing the effectiveness of the drug and
the occurrence of any adverse effects associated
with drug therapy.
■
■
Examine the skin for any rash or lesions
to provide
a baseline for possible adverse effects.
