(2) Secondary tissue schizonticides. These drugs destroy the secondary
tissue schizonts in the liver and thus prevent the relapsing fevers characteristic of P.
vivax, P. malariae, and P. ovale (but not characteristic of P. falciparum, the most lethal
form of malaria). Primaquine serves this purpose also.
(3) Blood schizonticides. These drugs destroy the schizonts and
merozoites in the red blood cells and thus relieve the symptoms of malarial infection.
They include quinine, quinacrine, and chloroquine. These drugs are often capable of
curing malaria because of P. falciparum.
b. Drugs Useful in the Prevention of Transmission of Malaria. The following
two categories of drugs do not necessarily help the immediate client, but they do help
prevent transmission to other people by way of mosquitoes.
(1) Gametocides. These drugs (primaquine is an example of this category
too) prevent mosquitoes from acquiring the infection from a client by destroying the
gametocytes in the client's blood.
(2) Sporontocides. The sporontocidal drugs (for example, pyrimethamine)
act inside the mosquito after it has ingested the client's blood. There they prevent the
reproduction of the zygote, the formation of sporozoites.
6-19. CHLOROQUINE AND PRIMAQUINE PHOSPHATE TABLETS
a. Action and Uses. The standard chloroquine-primaquine (CP) tablet is used
for malaria prophylaxis in all geographic areas where malaria is endemic. Each tablet
contains 500-mg of chloroquine phosphate (equivalent to 300-mg of chloroquine base),
which is a blood schizonticide for all four types of malaria mentioned above. It is thus
used to prevent the appearance of symptoms of malaria. The 79-mg of primaquine
phosphate (equivalent to 45 mg of primaquine base) in each tablet acts to destroy the
primary tissue schizonts of P. falciparum or P. vivax and the secondary tissue schizonts
of the malarias characterized by relapses, that is, P. vivax, P. malariae, and P. ovale.
(Thus, primaquine can be used to cure malaria as well as to prevent it or treat its
symptoms. However, CP tablets should NOT be used for therapy of acute attacks of
malaria. The toxic effects of taking more than one CP tablet in 1 day are severe.)
b. Usual Dosage.
(1) Adults and children over 100 pounds: One tablet weekly on the same
day of each week, starting at least 1 day before entering the area. After leaving the
area, continue this schedule (one tablet weekly) for 8 weeks.