Biguanides - Proguanil

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Chapter: Essential pharmacology : Antimalarial Drugs

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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