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Classification of Antimalarial Drugs
Antimalarial drugs are classified based on their mechanisms of action and the stages at which they act on the malarial parasite.
Tissue Schizonticides
- Drug Example: Primaquine
- Mechanism: Acts on hepatic forms of Plasmodium, preventing relapse in P. vivax and P. ovale malaria.
- Therapeutic Uses: Radical cure and prevention of relapse.
- Adverse Effects: Nausea, abdominal cramps, hemolysis in G6PD deficiency.
- Contraindications: G6PD deficiency, pregnancy, severe hepatic impairment.
Blood Schizonticides
- Chloroquine
- Mechanism: Inhibits heme polymerase in Plasmodium.
- Therapeutic Uses: Treatment of uncomplicated malaria, prophylaxis.
- Adverse Effects: GI upset, pruritus, headache, visual disturbances.
- Contraindications: Psoriasis, epilepsy, retinal disease.
- Mefloquine
- Mechanism: Disrupts parasite's hemoglobin metabolism.
- Therapeutic Uses: Effective for chloroquine-resistant malaria.
- Adverse Effects: Neuropsychiatric symptoms, dizziness, GI upset.
- Contraindications: Psychiatric or seizure disorders.
- Quinine
- Mechanism: Interferes with hemoglobin digestion by the parasite.
- Therapeutic Uses: Severe and chloroquine-resistant malaria.
- Adverse Effects: Cinchonism, hypoglycemia, cardiac toxicity.
- Contraindications: G6PD deficiency, hypersensitivity.
- Artemisinin and Derivatives
- Mechanism: Produces free radicals damaging parasite proteins.
- Therapeutic Uses: First-line for severe malaria.
- Adverse Effects: Mild GI symptoms, fever.
- Contraindications: Hypersensitivity; caution in early pregnancy.
Gametocytocides
- Primaquine
- Mechanism: Destroys gametocytes, preventing transmission of P. falciparum.
- Therapeutic Uses: Reduces malaria spread.
- Adverse Effects: Hemolysis in G6PD deficiency, GI disturbances.
- Contraindications: G6PD deficiency, pregnancy.
- Artemisinin Derivatives
- Mechanism: Kills gametocytes of P. falciparum.
- Therapeutic Uses: Reduces transmission in combination therapies.
- Adverse Effects: Mild GI symptoms, dizziness.
- Contraindications: Hypersensitivity.
Prophylactic Drugs
- Doxycycline
- Mechanism: Inhibits protein synthesis in the parasite.
- Therapeutic Uses: Prophylaxis in areas with high resistance.
- Adverse Effects: Photosensitivity, GI upset, esophageal irritation.
- Contraindications: Pregnancy, children under 8 years.
- Proguanil
- Mechanism: Inhibits dihydrofolate reductase, blocking parasite DNA synthesis.
- Therapeutic Uses: Prophylaxis, often combined with atovaquone.
- Adverse Effects: GI upset, mouth ulcers, mild headache.
- Contraindications: Severe renal impairment.
