McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 1 2  Antiprotozoal agents

TABLE 12.1

DRUGS IN FOCUS Antimalarials

Drug name

Dosage/route

Usual indications

artemether-lumefantrine (Riamet)

Adults, adolescents and children over 35 kg or 12 years of age: six doses of four tablets over 60 hours 25 to <35 kg: 18 tablets over 60 hours 15 to <25 kg: 12 tablets over 60 hours 5 to <15 kg: 6 tablets over 60 hours Suppression: Adult and paediatric (>8 years and 50 kg): 100 mg PO daily, beginning 2 days prior to entering malaria area, continued throughout stay in the area, then for 2 weeks after leaving Suppression: Adult: 310 mg PO every week, beginning 1–2 week before exposure and continuing for 4 weeks after leaving endemic area Paediatric: 5 mg/kg/week, following adult schedule Acute attack: Adult: 800 mg PO, followed by 400 mg PO in 6–8 hours on two consecutive days Treatment: Adult: 1250 mg PO as a single dose Prevention: Adult: 250 mg PO once weekly, starting 1 week before travel and continuing for 4 weeks after leaving endemic area Paediatric: 15–19 kg,1/4 tablet; 20–30 kg, 1/2 tablet; 31–45 kg, 3/4 tablet; >45 kg, 1 tablet; once a week, starting 1 week before travel and continuing until 4 weeks after leaving area Adult: 800 mg PO, followed by 400 mg PO in 6–8 hours on consecutive days.

Treatment of acute, uncomplicated malaria due to Plasmodium falciparum

doxycycline (Doryx, Frakas)

Prevention of Plasmodium falciparum malaria Prevention of Plasmodium vivax malaria in combination

Treatment of Plasmodium malaria in combination with other drugs, particularly primaquine

hydroxychloroquine (Plaquenil)

mefloquine (Lariam)

Prevention and treatment of Plasmodium malaria in combination with other drugs

primaquine (Primacin)

Prevention of relapses of P. vivax and P. malariae infections; radical cure of P. vivax malaria Treatment of malaria due to strains of P. falciparum resistance to 4-amnoquinolones

quinine (Quinbisul)

600 mg PO t.d.s. for 7–14 days

treatment of malaria caused by these resistant strains. Box 12.3 lists the antibiotics used to treat malaria. See Table 12.1 for usual indications. Mechanisms of action are as follows: • Hydroxychloroquine inhibits parasite reproduction, and by blocking the synthesis of protein production, it can cause the death of the Plasmodium . This drug is used in combination therapy, usually with primaquine, for greatest effectiveness. • Mefloquine increases the acidity of plasmodial food vacuoles, causing cell rupture and death. In combination therapy, mefloquine is used in malarial prevention, as well as treatment. • Primaquine, another very old drug for treating malaria, similar to quinine, disrupts the mitochondria of the Plasmodium . It also causes death of gametocytes and

exoerythrocytic (outside of the red blood cell) forms and prevents other forms from reproducing.

Pharmacokinetics Chloroquine is readily absorbed from the gastrointesti- nal (GI) tract, with peak serum levels occurring in 1 to 6 hours. It is concentrated in the liver, spleen, kidney and brain and is excreted very slowly in the urine, pri- marily as an unchanged drug. Hydroxychloroquine is readily absorbed from the GI tract, with peak serum levels occurring in 1 to 6 hours. It is excreted slowly in the urine, primarily as an unchanged drug. Mefloquine is a mixture of molecules that are absorbed, metabolised and excreted at different rates. The terminal half-life is 13 to 24 days. Metabolism