Anti Malarial Drugs
8:58 AM Edit This 0 Comments »#General Classification:
1. According to anti malarial activity:
1.Tissue schizonticides for causal prophylaxis: These drugs act on the primary tissue forms of the plasmodia which after growth within the liver, initiate the erythrocytic stage. By blocking this stage, further development of the infection can be theoretically prevented. Pyrimethamine and Primaquine have this activity. However since it is impossible to predict the infection before clinical symptoms begin, this mode of therapy is more theoretical than practical.
2.Tissue schizonticides for preventing relapse: These drugs act on the hypnozoites of P. vivax and P. ovale in the liver that cause relapse of symptoms on reactivation. Primaquine is the prototype drug; pyrimethamine also has such activity.
3.Blood schizonticides: These drugs act on the blood forms of the parasite and thereby terminate clinical attacks of malaria.These are the most important drugs in anti malarial chemotherapy. These include chloroquine, quinine, mefloquine, halofantrine, pyrimethamine, sulfadoxine, sulfones, tetracyclines etc.
4.Gametocytocides: These drugs destroy the sexual forms of the parasite in the blood and thereby prevent transmission of the infection to the mosquito. Chloroquine and quinine have gametocytocidal activity against P. vivax and P. malariae, but not against P. falciparum. Primaquine has gametocytocidal activity against all plasmodia, including P. falciparum.
5.Sporontocides: These drugs prevent the development of oocysts in the mosquito and thus ablate the transmission. Primaquine and chloroguanide have this action.
Thus in effect, treatment of malaria would include a blood schizonticide, a gametocytocide and a tissue schizonticide (in case of P. vivax and P. ovale). A combination of chloroquine and primaquine is thus needed in ALL cases of malaria.
2. According to the structure:
| Aryl amino alcohols: | Quinine, quinidine (cinchona alkaloids), mefloquine, halofantrine. |
| 4-aminoquinolines: | Chloroquine, amodiaquine. |
| Folate synthesis inhibitors: | Type 1 - competitive inhibitors of dihydropteroate synthase - sulphones, sulphonamides
|
| 8-aminoquinolines: | Primaquine, WR238, 605 |
| Antimicrobials: | Tetracycline, doxycycline, clindamycin, azithromycin, fluoroquinolones |
| Peroxides: | Artemisinin (Qinghaosu) derivatives and analogues - artemether, arteether, artesunate, artelinic acid |
| Naphthoquinones: | Atovaquone |
| Iron chelating agents: | Desferrioxamine |
!!Quick comparison between blood schizonticidal drugs
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| |||||
| Efficacy | ++++ | ++ | +++ | +++ | +++++ |
| Onset of action | Rapid | Slow | Rapid | Rapid | Fastest |
| Use | Prototype drug, first choice for all cases | Only for uncomplicated, resistant
| Only for resistant
| Only for uncomplicated, multi drug resistant
| Reserved for drug resistant
|
| Use in severe
| Parenteral preparation can be used in areas with sensitive strains | Not useful in acute illness; can be co- prescribed with other parenteral antimalarials | Drug of choice for severe malaria; it was the only parenteral drug available for a long time until parenteral chloroquine and artemisinin arrived | Not to be used in acute illness; can be co-prescribed with artemisinin after acute phase is over. | Useful in severe malaria; may be more effective and better tolerated than quinine. |
| Toxicity | ++ | +++ | +++ | +++ | + |
| Contra indications | Almost none, only advanced liver disease | Allergy to sulpha | Prior hypersensitive reactions | Epilepsy, psychosis, heart block, ß blocker use | None |
| Use in pregnancy | Yes | Only in 2nd trimester if warranted | Only if warranted, watch for hypoglycemia | Not in first trimester | Yes, if the situation demands |
| Cost | Cheapest | Cheap | Moderate | Expensive | Expensive |
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