It is a slowacting erythrocytic schizontocide which also inhibits the preerythrocytic stage of falciparum. Gametocytes exposed to proguanil are not killed but fail to develop properly in the mosquito.
BIGUANIDES
Proguanil (Chloroguanide)
It is a slowacting
erythrocytic schizontocide which also inhibits the preerythrocytic stage of falciparum. Gametocytes exposed to
proguanil are not killed but fail to develop properly in the mosquito. It is
cyclized in the body to a triazine derivative (cycloguanil) which inhibits plasmodial
DHFRase in preference to the mammalian enzyme. Resistance to proguanil develops
rapidly due to mutational changes in the plasmodial DHFRase enzyme.
Proguanil is slowly but adequately absorbed from the gut; is
partly metabolized and excreted in urine; t½ is 16–20 hr; noncumulative. It is
very well tolerated; side effects are less compared to chloroquine; mild
abdominal upset, vomiting, occasional stomatitis, haematuria, rashes and
transient loss of hair are reported.
In the late 1940s and early 1950s it was extensively used as a
clinical curative for vivax malaria. Such use is discouraged by its slow
response (cannot be depended upon in the nonimmune subject), and chances of
rapid resistance. Current use of proguanil is restricted to prophylaxis of
malaria in combination with chloroquine in areas of low level chloroquineresistance
among P. falciparum. It can be
employed during pregnancy.
Dose for malaria
prophylaxis: 200 mg daily with chloroquine
300 mg weekly till 4 weeks after exposure; LAVERAN, PROGUNAL 100
mg tab.
Because it potentiates atovaquione, a combination of the two has
been used in Thailand and some other countries for treatment of multi-drugresistant
falciparum malaria.
Chlorproguanil
It is proguanil with an additional chlorine substitution,
but with similar properties. Combined with dapsone, it has been used for
prophylaxis and treatment of chloroquine-resistant malaria. Along with
artesunate, the combination is being evaluated as ACT.
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