Artemisinin based drugs have in this decade been made the first line antimalarial drugs for Africa3, 8. Artemisinin based antimalarials are therefore consumed daily by millions of Africans. A disturbing feature of malaria treatment with artemisinin drugs is that although they are highly efficacious in eliminating clinical malaria symptoms, malaria treated with artemisinin drugs has high recrudescence rate of sometimes over 50% especially with 7 day oral treatments1, 3. A review of the results we obtained in a study on the effects of dihydroartemisinin 5 days and 7 days oral (DHA) treatments on the blood of Wistar albino rats showed that 5 days treatments produced the maximal effects of DHA on the blood (elevation of the packed cell volume (PCV) and the total white blood cell (WBC) count). The intense physiological effects of 5 days DHA treatments produced an auto-inhibitory feed-back effect on the DHA Effects on the blood cells. This inhibitory feed-back effect of DHA on itself caused all the stimulatory effects of DHA on the blood to be slowed down. The net effect of the negative feed-back effect of DHA on its own maximal effects was that the pharmacological effects of 7 days DHA treatments were lower than those of 5 days DHA treatments and the effects of 80mg/ Kg DHA was lower than those of 60mg/ Kg and 2mg/ Kg DHA. The study also showed that effects of DHA on the PCV and the WBC of treated albino rats were increased by repetition of the same dosage regimen after an interval of one week. Five dosage regimen of DHA were used in the study. The doses of DHA administered were 1mg/Kg, a repeated 1mg/Kg dose, 2 mg/ Kg, 60mg/ Kg and 80 mg/Kg. The response curve for 5 days and 7 days DHA treatments were similar and the maximal response dose for the 5 days and 7 days treatments was the same (2 mg/ Kg). The results of the study showed that the effects of DHA were dose, repetition and time dependent. The findings of the study suggest that a self regulating negative feed-back effect of DHA on its own effects on the body is responsible for the safety and high recrudescence of oral dihydroartemisinin.
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