These are drugs used for prophylaxis, treatment and prevention of relapses of malaria.
ANTIMALARIAL DRUGS
These are drugs used
for prophylaxis, treatment and prevention of relapses of malaria.
Malaria, caused by 4
species of the protozoal parasite Plasmodium,
is endemic in most parts of India and other tropical countries. It is one of
the major health problems. As per latest WHO estimates there are 300–500
million new clinical cases globally and >1 million deaths occur due to
malaria each year, 90% of which are in Africa. In India the National Malaria
Eradication Programme (NMEP), started in 1958, achieved near complete
disappearance of the disease in 1960s (from 75 million cases in 1950s to 0.1 million
cases in 1960s). However, due to the development of insecticide resistance
among mosquitoes and other factors, it staged a comeback in the mid 1970s (6.47
million cases in 1976), and continues to prevail in endemic/subendemic
proportions in different areas. Conceding that eradication of malaria is not
possible, NMEP was renamed National Antimalaria Programme (NAMP). Its scope has
now been widened to include other vector borne diseases, and it is called
‘National vector borne diseases control programme’ (NVBDCP). For the year 2005,
the NVBDCP has reported 1.8 million slide proven malaria cases in India, out of
which ~ 44% were falciparum malaria with 963 deaths. The WHO estimates that
actual number of malaria cases in India is 6 times more, i.e. ~12 million.
The bark of Cinchona tree, growing in Peru, was
introduced in Europe in the early 17th century as a cure for fevers. Later it
was realized to be a specific remedy for malaria. Quinine, isolated from
Cinchona bark in 1820, replaced the crude
preparation and continued to be the major antimalarial drug till 1942. The
world’s supply of Cinchona bark for
producing quinine was met by Java and neighbouring countries. This was cut off
from the Germans during World War I and from the Allies during World War II.
Due to enormous military importance of malaria and its treatment, intense
activity was initiated for the development of antimalarial drugs. Mepacrine was produced in Germany in
1926 and extensively field tested by the Allies during World War II. Chloroquine was produced in USA soon
after as a less toxic alternative to mepacrine. It had already been synthesized
and used by Germans in 1934 as ‘Resochin’. Proguanil
was introduced in 1945 by the British as a well tolerated clinical curative.
None of the above
drugs were found to be capable of preventing relapses in vivax malaria. Pamaquine was the first 8aminoquinoline
to be tested in Germany in the 1920s. However, no attention was paid to it
because of its poor schizontocide action. This class of drugs was retested
during World War II as radical curative and Primaquine
emerged as the most desirable drug. Pyrimethamine
was produced in 1951 under a planned postwar research programme for antimalarial
drugs. The important additions of the recent years are Mefloquine, Artemisinin and its derivatives/congeners, pyronaridine and few other synthetic
compounds for resistant falciparum malaria.
Classification
1. 4-Aminoquinolines: Chloroquine, Amodiaquine, Piperaquine.
2. Quinoline-methanol: Mefloquine.
3.
Cinchona alkaloid: Quinine, Quinidine
4.
Biguanides:
Proguanil (Chloroguanide), Chlorproguanil
5. Diaminopyrimidines:
Pyrimethamine
6. 8-Aminoquinoline:
Primaquine, Bulaquine
7. Sulfonamides
and sulfone: Sulfadoxine, Sulfamethopyrazine, Dapsone
8.
Tetracyclines: Tetracycline, Doxycycline
9.
Sesquiterpine Lactones : Artesunate, Artemether, Arteether
10.Amino
Alcohols: Halofantrine,
Lumefantrine
11.
Mannich Base: Pyronaridine
12.
Naphthoquinone: Atovaquone
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