McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 1 2  Antiprotozoal agents

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) 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 Injection: 4 mg/kg per day IM or IV for 14 days 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 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

Prevention and treatment of Pneumocystis carinii pneumonia; used in combination

with proguanil for treatment of chloroquine-resistant malaria

Treatment of amoebiasis, trichomoniasis, giardiasis

metronidazole (Flagyl, Metronide)

pentamidine (DBL Pentamidine, Isethionate for Injection)

As inhalation treatment of P. carinii pneumonia; as a systemic agent in the treatment of trypanosomiasis and leishmaniasis

pyrimethamine (Daraprim)

Treatment of toxoplasmosis

tinidazole (Fasigyn, Simplotan)

Treatment of trichomoniasis, giardiasis, amoebiasis

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

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.