C H A P T E R 1 2
Antiprotozoal agents
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and could have severe adverse effects on the infant.
The
safety and efficacy of pentamidine in children have not
been established. Tinidazole and metronidazole should
never be combined with alcohol and should be used with
caution in people with renal dysfunction,
which could
interfere with excretion of the drug.
Adverse effects
Adverse effects that can be seen with these antiprotozoal
agents include CNS effects such as headache, dizziness,
ataxia, loss of coordination and peripheral neuropathy
related to drug effects on the neurons. GI effects include
nausea, vomiting, diarrhoea, unpleasant taste, cramps
and changes in liver function. Superinfections can also
occur when the normal flora are disrupted.
Clinically important drug–drug interactions
Tinidazole and metronidazole should not be combined
with alcohol, which could cause severe adverse effects;
individuals are advised to avoid alcohol for at least 3 days
TABLE12.2
DRUGS IN FOCUS Other antiprotozoals
Drug name
Dosage/route
Usual indications
atovaquone (Wellvone)
Prevention:
Adult and paediatric (>13 years): 1500 mg/day
PO
Treatment:
Adult and paediatric (>13 years): 750 mg PO
b.d. with meals for 12 days (treatment)
Prevention and treatment of Pneumocystis
carinii pneumonia; used in combination
with proguanil for treatment of
chloroquine-resistant malaria
metronidazole (Flagyl,
Metronide)
Amebiasis:
Adult: 750 mg PO t.d.s. for 5–10 days
Paediatric: 35–50 mg/kg per day PO in three
divided doses for 10 days
Trichomoniasis:
Adult: 2 g PO as one dose, or divided into two
doses given on the same day or 250 mg PO
t.d.s. for 7 days
Paediatric: 5 mg/kg per dose PO t.d.s. for
7 days
Treatment of amoebiasis, trichomoniasis,
giardiasis
pentamidine (DBL
Pentamidine, Isethionate
for Injection)
Injection: 4 mg/kg per day IM or IV for 14 days
As inhalation treatment of P. carinii
pneumonia; as a systemic agent in
the treatment of trypanosomiasis and
leishmaniasis
pyrimethamine (Daraprim)
Adult: 50–75 mg/day PO with 1–4 g of a
sulfonamide for 4–5 weeks
Paediatric (>6 years): same as adult
Paediatric: 1 mg/kg/day PO, divided into two
equal doses, for 2–4 days; then cut dose in
half and continue for 1 month
Treatment of toxoplasmosis
tinidazole (Fasigyn,
Simplotan)
Trichomoniasis, giardiasis:
Adult: 2 g PO as a single dose with food
Paediatric (≥3 years): 50 mg/kg PO as a single
dose with food
Amoebiasis:
Adult: 2 g/day PO with food for 3 days
Paediatric (≥3 years): 50 mg/kg per day PO
with food, do not exceed 2 g/days
Treatment of trichomoniasis, giardiasis,
amoebiasis
Prototype summary: Metronidazole
Indications:
Acute intestinal amoebiasis, amoebic
liver abscess, trichomoniasis, acute infections
caused by susceptible strains of anaerobic bacteria,
and preoperative and postoperative prophylaxis for
people undergoing colorectal surgery.
Actions:
Inhibits DNA synthesis of specific
anaerobes, causing cell death; mechanism of action
as an antiprotozoal and amoebicidal is not known.
Pharmacokinetics:
Route
Onset
Peak
Oral
Varies
1–2 hours
IV
Rapid
1–2 hours
T
1/2
:
6 to 8 hours; metabolised in the liver and
excreted in the urine and faeces.
Adverse effects:
Headache, dizziness, ataxia, nausea,
vomiting, metallic taste, diarrhoea, darkening of
the urine.
