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Mefloquine was born during the Vietnam war, as a result of
research into newer anti malarials, to protect the American soldiers from the multi drug
resistant falciparum malaria. Nothing much has happened after that and hence this 'new'
drug should be restricted for use against multi drug resistant falciparum only.
Anti malarial activity: Mefloquine has been
found to produce swelling of the P. falciparum food vacuoles. It may act by forming toxic
complexes with free heme that damage membranes and interact with other plasmodial
components. It is effective against the blood forms of falciparum malaria, including the
chloroquine resistant types.
Absorption, fate and excretion:
Mefloquine is available for oral administration only because parenteral preparations cause
severe local reactions. It is absorbed rapidly and is extensively bound to plasma
proteins. Elimination half-life is about 2-3 weeks. It is mainly excreted in the faeces.
Toxicity: It is generally well
tolerated in therapeutic doses up to 1500 mg. Nausea, vomiting, abdominal pain and
dizziness can occur in doses exceeding 1 g. Less frequently it can cause nightmares,
sleeping disturbances, dizziness, ataxia, sinus bradycardia, sinus arrhythmia, postural
hypotension, and an 'acute brain syndrome' consisting of fatigue, asthenia, seizures and
psychosis. Mefloquine should be used with caution in patients with heart block, patients
taking beta blockers, patients with history of epilepsy and psychiatric disease. It should
be avoided in first trimester of pregnancy and pregnancy should be avoided within 3 months
of taking the drug.
Contraindications: It should not
be used for prophylaxis in pregnancy, particularly during the first trimester. It is
contraindicated in patients with history of seizures, severe neuropsychiatric
disturbances, or adverse reactions to quinoline antimalarials like chloroquine and
quinine. It should not be used concomitantly with these drugs for increased risk of
cardiotoxicity and risk of convulsions. Mefloquine is reported to increase the risk of
seizures in patients taking valproate. It may compromise adequate immunisation by live
typhoid vaccine. Patients taking mefloquine should refrain from driving or operating
machinery.
Availability: It is available as
250 mg tablets.
Dose: 15 mg/kg in a single dose.
If the dose exceeds 1000 mg, the second dose can be given after 4-8 hours to minimise
gastric irritation. Total dose should not exceed 1500 mg.
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