Introduction ORIGINAL ARTICLE. Akihiro Hitani Tetsuya Nakamura Hiroshi Ohtomo Yukifumi Nawa Mikio Kimura

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1 J Infect Chemother (2006) 12: Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases 2006 DOI /s ORIGINAL ARTICLE Akihiro Hitani Tetsuya Nakamura Hiroshi Ohtomo Yukifumi Nawa Mikio Kimura Efficacy and safety of atovaquone-proguanil compared with mefloquine in the treatment of nonimmune patients with uncomplicated P. falciparum malaria in Japan Received: March 1, 2006 / Accepted: July 13, 2006 Abstract Malaria treatment is becoming increasingly difficult due to the widespread drug resistance of Plasmodium falciparum. In Japan, only three antimalarials are approved for treatment: oral quinine, sulfadoxinepyrimethamine, and mefloquine. Recently, however, the Research Group on Chemotherapy of Tropical Diseases introduced atovaquone-proguanil for treating drugresistant P. falciparum malaria. This research group had also introduced mefloquine before it was licensed nationally. Using data obtained from the research group, we analyzed the efficacy and safety of atovaquone-proguanil, as compared with mefloquine, in nonimmune patients with uncomplicated P. falciparum malaria. Cures were attained in all (100%) of 20 atovaquone-proguanil-treated and 49 (98%) of 50 mefloquine-treated adults. The mean fever clearance time (FCT) and parasite clearance time (PCT) appeared to be longer in the atovaquone-proguanil group than in the mefloquine group, but the differences were not statistically significant. Three (15%) of the 20 atovaquone-proguaniltreated adults had adverse events (AEs), all of which were transient elevations of liver enzymes, while 19 (38%) of the 50 mefloquine-treated adults had AEs, including dizziness in A. Hitani Healthcheck, Health Care Center, Medical Institute Zenjinkai, Yokohama, Japan T. Nakamura Department of Infectious Diseases and Applied Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan H. Ohtomo Department of Tropical Medicine, Jikei University School of Medicine, Tokyo, Japan Y. Nawa University of Miyazaki, Miyazaki, Japan M. Kimura (*) Infectious Disease Surveillance Center, National Institute of Infectious Diseases, Toyama , Shinjuku-ku, Tokyo , Japan Tel , ext. 2043; Fax kimumiki@nih.go.jp A. Hitani, T. Nakamura, H. Ohtomo, Y. Nawa, M. Kimura Research Group on Chemotherapy of Tropical Diseases, Japan 8 (16%) and nausea/vomiting in 7 (14%). All 3 children treated with atovaquone-proguanil were cured without developing AEs. Despite the limitations of this study in not being a formal clinical trial, atovaquone-proguanil seemed to be at least equal to, or even better than, mefloquine for the treatment of uncomplicated P. falciparum malaria in nonimmune patients, including children. Its marketing in Japan could be beneficial in offering an alternative therapeutic option. However, vigilance should be maintained on the possible occurrence of rare but severe AEs, and also of the possible spread of drug resistance. Key words Atovaquone-proguanil Mefloquine Plasmodium falciparum Malaria Non-immune patients Drug resistance Introduction Malaria is one of the most important potentially life-threatening infectious diseases among international travelers from industrialized countries to tropical/subtropical countries. An estimated European and North American travelers get malaria annually, 1 and the case fatality rates for Plasmodium falciparum malaria are 1% 2% in most of these countries. 2 Treatment is becoming increasingly difficult due to the widespread drug resistance of P. falciparum; the occasional adverse events (AEs) of existing therapeutic antimalarials also pose a problem. Therefore, the development of more effective antimalarials which patients are more able to tolerate has long been awaited. Atovaquone-proguanil is a fixed-dose combination drug of atovaquone and proguanil hydrochloride developed against drug-resistant P. falciparum malaria, 3 and has been commercially available around the world since the late 1990s. Previous studies conducted on semiimmune individuals with uncomplicated P. falciparum malaria in endemic areas such as Thailand, 4 Philippines, 5 Brazil, 6 and sub-saharan Africa 7,8 showed its excellent efficacy and safety. Recent studies carried out on nonimmune travelers also showed promising results. 9 11

2 278 In Japan, the annual number of malaria cases reported under the national infectious disease surveillance scheme ranged from 50 to 80 during the 1990s. 12 After a peak figure of 154 recorded in 2000, the numbers are declining, with cases reported annually during Only three antimalarials are approved for treatment in Japan: oral quinine, sulfadoxine-pyrimethamine, and mefloquine. Due to the poor toleration of oral quinine and the emerging resistance of P. falciparum to sulfadoxine-pyrimethamine, mefloquine has been used preferentially for uncomplicated P. falciparum malaria, especially since it was licensed in However, concern has been raised about its AEs, and especially about the potentially severe neuropsychiatric AEs, which occur more frequently in treatment than in prophylaxis. 14 The Research Group on Chemotherapy of Tropical Diseases, Japan, introduced mefloquine before it was licensed nationally, and treated a number of patients. 12 Later, in 1999, the research group also introduced atovaquone-proguanil, and to date has used it to treat at least 20 nonimmune adults and 3 nonimmune children with uncomplicated P. falciparum malaria. We evaluated the efficacy and safety of atovaquone-proguanil as compared with mefloquine using data obtained from the research group. Although this study was not a formal clinical trial, and thus the results may have limitations for interpretation, it could contribute to clarifying the role of atovaquoneproguanil for the treatment of imported uncomplicated P. falciparum malaria in Japan. Materials and methods The research group and the use of drugs The Research Group on Chemotherapy of Tropical Diseases was established in 1980 and is currently funded by the Japan Health Sciences Foundation. 12 The group is primarily aimed at importing and distributing drugs for tropical and parasitic diseases that are not licensed in Japan, so that patients with those diseases can receive adequate treatment. The drugs introduced by the research group include several antimalarials as well as drugs for amebiasis, leishmaniasis, trypanosomiasis, fascioliasis, and cryptosporidiosis. The drugs are examined at the National Institute of Health Sciences for their chemical composition, and in particular for whether they meet the Japanese Good Manufacturing Practice standards. Subsequently, they are distributed to 20 medical facilities throughout Japan, so that they can be available in any area without significant delay. In principle, approval is obtained from the ethical committee of the medical facilities concerned for participation in this program. The drugs are used at those facilities after obtaining the patient s informed consent, which clearly states that the drugs are not licensed in Japan, but are licensed in Western countries. In exceptional cases where the patient cannot be referred to one of those medical facilities, e.g., due to the severity of the disease, the drugs can be used outside the designated medical facilities. After performing patient evaluations following treatment, the physicians in charge are asked to fill in the patient records. The patient record sheets were formulated by the research group. Analysis and patients Only patient records with sufficient information were used in this study. When necessary, we contacted the physicians in charge directly to obtain more detailed information. The selection of antimalarials used for the treatment was primarily carried out by the physicians. None of the enrolled cases received antimalarials other than atovaquone-proguanil or mefloquine unless those antimalarials were judged to be ineffective. Uncomplicated P. falciparum malaria was defined as the absence of complications of malaria that constitutes severe P. falciparum malaria, as proposed by the expert committee of the World Health Organization (WHO). 15 Nonimmune individuals were defined as travelers from nonendemic countries (mostly Japan) to endemic countries, or those who had lived in nonendemic countries (mostly Japan) for at least 1 year. 9 We enrolled 20 nonimmune adults with uncomplicated P. falciparum malaria who were treated with atovaquoneproguanil (one tablet = 250 mg atovaquone mg proguanil hydrochloride, Malarone; GlaxoSmithKline, North Carolina, USA), 4 tablets daily for 3 successive days, during In addition, 3 nonimmune children with uncomplicated P. falciparum, aged 1 year and 11 months (12.5kg), 4 years and 1 month (15.7kg), and 5 years and 8 months (19.0 kg), who all had contracted malaria in sub- Saharan countries, were enrolled. They received 1 tablet of atovaquone-proguanil daily for 3 successive days. Atovaquone-proguanil was generally taken together with a meal or with milk products. As another treatment arm, we enrolled 50 nonimmune adults with uncomplicated P. falciparum malaria who had been treated during with mg/kg mefloquine (Mephaquin; Mepha, Aesch- Basel, Switzerland), divided into 1 3 doses. Gastric drugs were usually taken concomitantly with mefloquine to prevent vomiting. Efficacy and safety of antimalarials The efficacy was evaluated as the final outcome of the patients, i.e., the cure rate, as well as the fever clearance time (FCT) and parasite clearance time (PCT). 4 The FCT was the period from the initiation of treatment until the body temperature decreased to 37.0 C or below and remained there for at least 1 day thereafter. The PCT was the period from the initiation of treatment until microscopy of Giemsa-stained blood films became negative for asexual forms of P. falciparum. AEs were evaluated from the physicians description as well as by our judgments on laboratory data described in

3 279 the patient records. The severity and duration of the AEs were also assessed. described after antimalarial treatment varied and were relatively short, mostly 7 10 days. Statistical analyses All statistical procedures were performed with Statcel2 (OMS Publishing). Comparisons between two averages were conducted as follows. If both the groups showed a normal distribution and equal variance, Student s t-test was used, and if both the groups showed a normal distribution but not an equal variance, Welch s test was used. If at least one of the two groups did not show a normal distribution, the Mann Whitney U-test was used. Comparisons between two percentages were conducted with Fisher s exact test. Results Patient characteristics, pretreatment conditions, and follow-ups Demographics (age, body weight, sex, and destination) and pretreatment indicators of disease severity (hemoglobin, platelet count, and parasite count) were compared between 20 atovaquone-proguanil-treated and 50 mefloquinetreated nonimmune adults with uncomplicated P. falciparum malaria (Table 1). The mean age was significantly lower in the atovaquone-proguanil group than in the mefloquine group. However, no statistically significant differences were found in the pretreatment indicators of disease severity. Thus, overall, the two treatment groups were considered to be comparable. For the 3 nonimmune children with uncomplicated P. falciparum malaria, the mean platelet and parasite counts were /µl (range ) and 48700/µl (range ), respectively. Due to the limitations of this study, the follow-up periods Efficacy of antimalarials All (100%) the 20 atovaquone-proguanil-treated and 49 (98%) of the 50 mefloquine-treated adults were cured (Table 1). The mean FCT and PCT in the atovaquoneproguanil group (3.7 and 3.3 days, respectively) appeared to be longer than those of the mefloquine group (2.9 and 2.8 days, respectively), but the differences were not statistically significant. One patient, who fell ill after visiting Ghana, was not cured by treatment with 15 mg/kg mefloquine divided into two doses. Although the parasite count declined on day 2 of treatment, it increased significantly on day 3, with some visible P. falciparum ring forms showing intact morphology. This prompted the physician to judge the case a treatment failure and switch to sulfadoxine-pyrimethamine, which ultimately led to a complete cure. All 3 children were also cured in due course, with a mean FCT of 1.8 days and a mean PCT of 3.7 days. AEs of antimalarials AEs were compared between the 20 and 50 adults treated with atovaquone-proguanil and mefloquine, respectively (Table 2). AEs were reported in 3 (15%) of the 20 patients in the atovaquone-proguanil group, and all of these were transient elevations of liver enzymes. Two patients showed an increase in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels (around 100 IU/l), but not in their total bilirubin level. These abnormal values subsequently subsided within 2 4 weeks. The third patient showed a slightly greater increase in AST (around 160) and ALT (around 190), with a total bilirubin level of 2.0mg/dl (direct, 1.4). However, these values became normalized Table 1. Demographics and pre- and post-treatment data for two treatment groups composed of nonimmune adults with uncomplicated P. falciparum malaria Parameter Subjects who received: P Atovaquone-proguanil Mefloquine (n = 20) (n = 50) Demographics Mean age ± SD (years) 32.4 ± ± Mean body weight ± SD (kg) 65.6 ± ± No. (%) of male patients 15 (75) 42 (84) 0.89 No. (%) of patients infected in sub-saharan Africa 19 (95) 40 (80) 0.11 Pretreatment Mean hemoglobin ± SD (g/dl) 14.3 ± ± Mean platelet count ± SD ( 10 3 /µl) 118 ± ± Mean parasite count (range) (/µl) ( ) ( ) 0.68 Posttreatment No. (%) of patients cured 20 (100) 49 (98) 0.71 Mean fever clearance time ± SD (days) 3.7 ± ± Mean parasite clearance time ± SD (days) 3.3 ± ±

4 280 Table 2. Adverse events (AEs) in two treatment groups composed of nonimmune adults with uncomplicated P. falciparum malaria Indicator Subjects with AEs who received: P Atovaquone-proguanil Mefloquine (n = 20) (n = 50) No. % No. % Any AEs Nausea/vomiting Diarrhea Abdominal pain Dizziness Insomnia Vivid dreams Itching/urticaria Elevated liver enzymes within 2 3 weeks without any specific treatment. In the mefloquine group, AEs were reported in 19 (38%) of the 50 patients, with some having more than one AE. The AEs included dizziness in 8 patients (16%), nausea/vomiting in 7 patients (14%), and diarrhea, vivid dreams, itching/urticaria, or elevated liver enzymes in 2 patients (4%) for each. No AEs were reported in the 3 children. Discussion Efficacy and safety data on the therapeutic use of atovaquone-proguanil for uncomplicated P. falciparum malaria in nonimmune patients have recently been published. A randomized, open-label study on French subjects compared atovaquone-proguanil (n = 25) and halofantrine (n = 23). 9 All assessable patients of the two treatment arms were cured, with the mean PCT being longer in the atovaquone-proguanil group than in the halofantrine group. Vomiting appeared at a significantly higher rate in the atovaquone-proguanil group. A Danish study enrolled 50 patients. 10 Although about half of them were Africans, most were considered to be nonimmune. All these patients were cured with atovaquone-proguanil without developing significant AEs. Interestingly, patients developing breakthrough malaria after chemoprophylaxis with chloroquine plus proguanil were also cured. A second French study showed that all 112 patients who were enrolled in it were cured with atovaquone-proguanil without significant AEs except for occasional, minor gastrointestinal symptoms. 11 Our study has limitations in that the described follow-up periods after treatment varied and were relatively short. However, those periods often reflected hospitalization only, and did not include the follow-ups conducted at an outpatient clinic after the patients were discharged. Furthermore, the physicians in charge had established a close relationship with the patients, enabling them to report any unusual events to the physicians. Accordingly, it is reasonable to assume that possible recrudesced cases or prominent AEs would have been detected. Thus, despite the relatively small number of cases and the limitations of the study, our results appear to be in line with the published data showing the excellent efficacy and safety of atovaquone-proguanil. This antimalarial could potentially be advantageous in cases contracted in border areas of Thailand, where the mefloquine resistance of P. falciparum has become prevalent, as suggested in one of the previously quoted articles. 4 Previous treatment studies have generally shown that atovaquone-proguanil is well tolerated and lacks significant neuropsychiatric AEs. In an extensive review, the most commonly reported AEs experienced in the treatment of adults with this agent included abdominal pain (17%), nausea (12%), vomiting (12%), headache (10%), diarrhea (8%), anorexia (5%), and dizziness (5%), with a few significant neuropsychiatric AEs. 16 Two randomized studies of nonimmune travelers on chemoprophylaxis showed that atovaquone-proguanil had fewer neuropsychiatric AEs than mefloquine. 17,18 Thus, our result of the lower incidence of all AEs due to atovaquone-proguanil, including neuropsychiatric ones such as insomnia, vivid dreams, and dizziness, is consistent with previous findings. Elevations of liver enzymes were reported in the Thai 4 and Zambian 8 studies, but they were mostly self-limiting and/or could also be due to the malaria itself, and not to AEs. Our findings on the three patients with elevated liver enzymes are largely in line with those previous findings. However, a recent report described a traveler on atovaquone-proguanil prophylaxis who developed acute hepatitis, i.e., increased levels of ALT (around 700), AST (around 200), and total bilirubin manifesting jaundice. 19 Due to the relatively short history of its use, we should be alerted to the possible occurrence of rare but severe AEs with atovaquone-proguanil, as its use will increase in future. Unlike quinine, quinidine, and halofantrine, which can alter cardiac conduction, atovaquoneproguanil was reported to have no such cardiotoxicity. 9,20 Children with P. falciparum malaria are likely to develop serious complications such as cerebral malaria, severe anemia, and hypoglycemia, and are less likely to comply with oral medication. Therefore, the availability of effective and tolerable antimalarials is crucial in treating pediatric malaria. Although published data are scarce, it is widely believed that atovaquone-proguanil is effective and safe in children, including those who are nonimmune. 21 Our results

5 281 of the treatment of 3 pediatric patients also support this finding, and details have been published elsewhere. 22 Recently, the United States Centers for Disease Control and Prevention recommended atovaquone-proguanil for the treatment of children weighing 5 kg or more, based on efficacy and safety data obtained in Gabon. 23 Concern has been raised about the potential useful life of atovaquone-proguanil, due to reports of the imported drug-resistant P. falciparum malaria identified in treatment but not in prevention. P. falciparum isolates from those cases had one of the two mutations Tyr268Asn 24 and Tyr268Ser on the cytochrome b gene, which could confer atovaquone resistance. In addition, a single case was reported that showed clinical atovaquone-proguanil resistance in treatment, but did not possess either of the codon 268 mutations. 29 When European investigators conducted a large-scale survey of putative drug resistance mutations using P. falciparum isolates from imported cases, they identified the Tyr268Ser but not the Tyr268Asn mutation in one of 504 isolates, corresponding to one out of 5 atovaquoneproguanil treatment failures. 30 Conceivably, mechanisms other than the mutations of Tyr268 may also be responsible for the development of atovaquone-proguanil resistance. A recent study showed long-lasting low concentrations of atovaquone in human plasma following atovaquoneproguanil administration, even up to the time when proguanil and its cycloguanil metabolite might not be detectable. 31 It is of concern that this pharmacokinetic property could facilitate the selection of P. falciparum that is resistant to atovaquone in the future. Despite the limitations of this study, atovaquoneproguanil seemed at least equal to, or even better than, mefloquine for treatment of uncomplicated P. falciparum malaria in nonimmune patients, including children. Its marketing in Japan could be beneficial in offering an alternative therapeutic option. However, vigilance should be maintained as to the possible occurrence of rare but severe AEs, and also of the possible spread of drug resistance as its use becomes widespread. Acknowledgments None of the authors has a conflict of interest related to this research. This study was supported in part by a research grant (KH42075) for Research on Health Sciences Focusing on Drug Innovation from the Japan Health Sciences Foundation. References 1. Lobel HO, Kozarsky PE. Update on prevention of malaria for travelers. JAMA 1997;278: Muentener P, Schlagenhauf P, Steffen R. Imported malaria ( ): trends and perspectives. Bull World Health Organ 1999;77: Shanks GD. Drugs used in malaria chemoprophylaxis. Atovaquone/proguanil. In: Schlagenhauf P, editor. Travelers malaria. Hamilton: BC Decker 2001: Looareesuwan S, Wilairatana P, Chalermarut K, Rattanapong Y, Canfield CJ, Hutchinson DBA. Efficacy and safety of atovaquone/ proguanil compared with mefloquine for treatment of acute Plasmodium falciparum malaria in Thailand. Am J Trop Med Hyg 1999;60: Bustos DG, Canfield CJ, Canete-Miguel E, Hutchinson DBA. Atovaquone-proguanil compared with chloroquine and chloroquine sulfadoxine-pyrimethamine for treatment of acute Plasmodium falciparum malaria in the Philippines. J Infect Dis 1999;179: de Alencar FEC, Cerutti C Jr, Durlacher RR, Boulos M, Alves FP, Milhous W, et al. Atovaquone and proguanil for the treatment of malaria in Brazil. J Infect Dis 1997;175: Radloff PD, Philipps J, Nkeyi M, Hutchinson D, Kremsner PG. Atovaquone and proguanil for Plasmodium falciparum malaria. Lancet 1996;347: Mulenga M, Sukwa TY, Canfield CJ, Hutchinson DBA. 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J Travel Med 2005;12: Gupta RK, van Vugt M, Paiphun L, Slight T, Looareesuwan S, White NJ, et al. No evidence of cardiotoxicity of atovaquoneproguanil alone or in combination with artesunate. Am J Trop Med Hyg 2005;73: Stauffer W, Fischer PR. Diagnosis and treatment of malaria in children. Clin Infect Dis 2003;37: Mizuno Y, Sato N, Hayakawa E, Matsushita T, Saegusa M, Kuboshima S. Three pediatric patients with falciparum malaria treated with atovaquone-proguanil. J Jpn Pediatr Soc 2006;110: (in Japanese with English abstract). 23. Borrmann S, Faucher JF, Binder RK, Miller GB, Lell B, Kremsner PG. Atovaquone and proguanil versus amodiaquine in the treatment of uncomplicated Plasmodium falciparum malaria in children weighing 5 and <11 kg in Gabon [poster 813]. Program and Abstracts of the 50th Annual Meeting of the American Society of Tropical Medicine and Hygiene (Atlanta). Northbrook, IL. American Society of Tropical Medicine and Hygiene 2001: Fivelman QL, Butcher GA, Adagu IS, Warhurst DC, Pasvol G. Malarone treatment failure and in vitro confirmation of resistance of Plasmodium falciparum isolate from Lagos, Nigeria. Malar J 2002;1: Schwartz E, Bujanover S, Kain KC. Genetic confirmation of atovaquone-proguanil-resistant Plasmodium falciparum malaria

6 282 acquired by a nonimmune traveler to East Africa. Clin Infect Dis 2003;37: David KP, Alifrangis M, Salanti A, Vestergaard LS, Rønn A, Bygbjerg I. Atovaquone/proguanil resistance in Africa: a case report. Scand J Infect Dis 2003;35: Färnert A, Lindberg J, Gil P, Swedberg G, Berqvist Y, Thapar MM, et al. Evidence of Plasmodium falciparum malaria resistant to atovaquone and proguanil hydrochloride: case reports. BMJ 2003; 326: Kuhn S, Gill MJ, Kain KC. Emergence of atovaquone-proguanil resistance during treatment of Plasmodium falciparum malaria acquired by a non-immune North American traveller to West Africa. Am J Trop Med Hyg 2005;72: Wichmann O, Muehlen M, Gruss H, Mockenhaupt FP, Suttorp N, Jelinek T. Malarone treatment failure not associated with previously described mutations in the cytochrome b gene. Malar J 2004;3: Wichmann O, Muehlberger N, Jelinek T, Alifrangis M, Peyerl- Hoffmann G, Mühlen M, et al. Screening for mutations related to atovaquone/proguanil resistance in treatment failures and other imported isolates of Plasmodium falciparum in Europe. J Infect Dis 2004;190: Edstein MD, Kotecka BM, Anderson KL, Pombo DJ, Kyle DE, Rieckmann KH, et al. Lengthy antimalarial activity of atovaquone in human plasma following atovaquone-proguanil administration. Antimicrob Agents Chemother 2005;49: