M. O. Raji & C. O. Bewaji 205 African Scientist Vol. 13, No. 4, December 31, 2012 1595-6881/2012 $5.00 + 0.00 Printed in Nigeria © 2012 Nigerian Society for Experimental Biology http://www.niseb.org/afs AFS 2012086/13407 Drug Resistance in Malaria Treatment Muizdeen Oyebode Raji and Clement O. Bewaji* Department of Biochemistry, University of Ilorin, Ilorin, Nigeria (Received July 6, 2012; Accepted September 8, 2012) ABSTRACT: According to the World Health Organization (WHO), malaria is one of the five leading causes of death in children under five years old. It has been estimated that over 1 million children die every year of malaria. In spite of the various research and control efforts on malaria, it is still one of the most devastating parasitic diseases in the tropics. Strategies that have been adopted to control or eradicate malaria include the use of residual (long-acting) insecticides to control the mosquito vectors and the introduction of new drugs for the prevention and treatment of malaria infection. The various control efforts had a setback as mosquitoes became resistant to insecticides and the malaria parasites became resistant to antimalarial drugs, notably chloroquine. Many other drugs that were introduced to malaria chemotherapy also subsequently became ineffective. The phenomenon of drug resistance and the underlying mechanism is the focus of this review. Keywords: Malaria; Drug resistance; Antimalaria drugs; Plasmodium species. 1.0. Introduction Drug resistance is a term used to describe the loss of effectiveness of antimicrobial or antitumor agents (Rang et al., 2003). It is the reduction in effectiveness of a drug such as antihelminthics, antibacterial, antimalarial, and cytotoxic agents. Antimalarial drug resistance has been defined as the “ability of a Plasmodium strain to survive and/or multiply despite the administration and absorption of a drug given in doses equal to or higher than those usually recommended but within tolerance of the subject”. This definition was later modified to specify that the drug in question must gain access to the parasite or the infected red blood cell for the duration of the time necessary for its normal action (WHO, 2001). 1.1. Overview of Malaria and Human Plasmodial Life Cycle Malaria is a disease caused by plasmodia infection by female anopheline mosquito. Human malaria is caused by four species of Plasmodium: Plasmodium falciparum, Plasmodium malariae, Plasmodium vivax, and Plasmodium ovale. Malaria symptoms include shivering, fever, sweating, anaemia, and death in some cases especially due to cerebral malaria in children and non-immune individuals (Willey et al., 2007). *To whom all correspondence should be addressed. E-mail: cobewaji@unilorin.edu.ng; Tel: +2348033576937