| DRUG
RESISTANT MALARIA |
- Literally speaking, drug resistant malaria means malaria
caused by a plasmodium resistant to usual antimalarial drugs.
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- Although chloroquine resistant strains of P. vivax have
been described, drug resistance poses a serious clinical
problem only with P. falciparum, which accounts for over
70% of cases and much of the mortality of human malaria.
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| Global
Scenario of Drug Resistant Malaria |
| P.
falciparum resistance |
- Chloroquine resistant strains of P. falciparum are found
now in nearly all areas of chloroquine use including South
America, Central America east of the Panama Canal, the Western
Pacific, East Asia and many regions of Africa south of the
Sahara.
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- Resistance to the combination of pyrimethamine and sulfadoxine
is prevalent in some areas of Southeast Asia, the Amazon
Basin of South America and many foci in sub-Saharan Africa.
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- Variable degrees of decreased responsiveness
to quinine and quinidine have been reported, though rarely,
in Southeast Asia and Oceania and apparently in sub-Saharan
Africa
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| P.
vivax resistance |
- Recent reports from Indonesia (Irian Jaya, Sumatra) and
Papua New Guinea indicate high levels of P. vivax schizonts
resistant to chloroquine. Decreased susceptibility may also
be appearing in the Solomon Islands, Myanmar, Brazil, Colombia.
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- Resistance of P. vivax blood schizonts to pyrimethamine
and sulfadoxine has been reported in many areas of the world,
particularly Southeast Asia.
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| P.
ovale and P. malariae resistance |
- P. ovale and P. malariae forms have not shown resistance
to chloroquine
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| Indian
Scenario of Drug Resistant Malaria |
- Of the two plasmodia which cause malaria in India, incidence
of drug resistance is more common with P. falciparum.
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- Occasionally, P. vivax may also be drug resistant and
this occurs specially as a result of improper treatment
and inadequate dosage.
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- Originally, both the Plasmodia - vivax and falciparum
- were sensitive to chloroquine, but, in recent years, more
and more P. falciparum are developing resistance against
chloroquine.
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- To overcome this problem of chloroquine resistance, Sulfadoxine
+ Pyrimethamine combination was used. But, very soon, some
strains of falciparum developed resistance to this combination
also.
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- P. falciparum resistant to traditional drugs like Quinine
have also been reported.
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- Incidence in India will be difficult to know because in
many cases it may not be recorded.
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- In India, the first confirmed report of chloroquine resistance
in P. falciparum was reported in Diphu area of Karbianglong
district of Assam in 1973.
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- A study carried out by the Clinical Pharmacological and
Research Services Unit, in KEM hospital in Mumbai, confirmed
the existence of chloroquine resistance in P. falciparum
cases in Mumbai, incidence being 5% to full dose chloroquine.
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- Resurgence of P. falciparum resistant to chloroquine has
been noticed in several regions of India. Earlier reports
indicated chloroquine resistance to P. falciparum in North
Eastern parts of the country with new foci of drug resistance
being added.
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| However for all practical purposes,
drug resistant malaria in the Indian context means malaria
caused by strains of P. falciparum which are resistant
to chloroquine. |
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| Types
of Drug Resistance |
- In defining criteria for resistance to the aminoquinoline
antimalarial drugs, the WHO has described three grades of
resistance following treatment
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- (Low grade) R1 : Recrudescence of infection between 7
and 28 days of completing treatment following initial resolution
of symptoms and parasite clearance.
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- (High grade) R2 : Reduction of parasitaemia by > 75%
at 48 hours but failure to clear parasites within 7 days.
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- R3 : Parasitaemia does not fall by >75% within 48 hours.
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| Causes
of Drug Resistance |
- Resistance occurs most commonly due to improper treatment
and inadequate dosage of antimalarial.
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- The possible mechanisms of development of resistance are
as follows:
i. Parasite does not allow the entry of drug.
ii. After entry of drug, the malarial parasite does not
retain it and throws it out.
iii. May be a combination of both.
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