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Plasmodium falciparum in Thailand is multi-drug resistant. In a previous study it was shown that artesunate and mefloquine were effective, as follow up, we monitored the efficacy of this regimen for six years. During 1997-2002, 516 adult male volunteer patients in Chanthaburi Province were enrolled (50 patients in the first year, 400 patients in 1998-2001 and 66 patients in 2002). The symptom complex and parasite count (thick blood film) were monitored on days 0, 1, 2, 7, 14, 21, 28, 35 and 42. The dosages used were artesunate (ATS) 150 mg and mefloquine (M) 750 mg at hour 0 and ATS 100 mg and M 500 mg at hour 24. Their ages ranged from 30-35 years and their mean body weights were 54-56 kg. The presenting symptoms were fever 100%, headache 97-100%, anorexia 78-90%, and nausea 28-40%. The geometric mean of parasitemia ranged from 7,357-12,750/mm3. Defervescence in one day was found in 42-76% of patients and 85-100% in 2 days. The sensitivity (S) ranged from 87-94% and RI resistance (recrudescence) ranged from 6-13%. Forty patients demonstrated RI type of response, 37 were cured after being retreated with the same dosage and another 3 patients were cured after the third course of treatment. The aggravated adverse effects included vomiting (8-20%), anorexia (1-41%) and diarrhea (0-16%). These side effects were mild and transient. The efficacy of the artesunate and mefloquine combination for the treatment of uncomplicated falciparum malaria was high. The RI type of response was possibly due to re-infection or multiple broods and not to drug resistance. The adverse effects of anorexia, nausea, vomiting and diarrhea were mild and transient for mefloquine. The combination can be used as stand by treatment in areas of multi-drug resistant falciparum malaria.

Twenty-eight male Thai patients with severe falciparum malaria were randomized to receive either artemether for a 5 (300 mg initial dose followed by 100 mg for another 4 days) or a 7 days regimen (160 mg initial dose, followed by 80 mg daily for another 6 days). Thirteen patients received a 5 day regimen and 15 received 7 day regimen. The follow-up period was 28 days. The patients in both groups were comparable in age, body weight, admission parasitemia, hematocrit and white cell count. There were 4 patients in each group who presented with cerebral malaria. The median values of parasite and fever clearance times (PCT and FCT) in the 5 and 7 days regimens were 52 vs 60 hours, and 85 vs 68 hours, respectively. There were 8 and 4 patients, respectively who had recrudescence during days 15 to 25. The cure rates were 38% (95% CI = 14-68%) and 73% (95% CI - 50-96%), respectively for 5 and 7 day regimens. None died in either group. No patients in either group had neurological sequelae after recovery of consciousness. Clinically adverse effects in either group were transient pain at the site of injection. No drug related biochemical or ECG changes were noted in either group. The duration of treatment is the determinant of the cure rate; however, the duration of even 7 days still resulted in high recrudescence rate. It may be necessary to combine artemether with other longer half-life antimalarials to improve the cure rate.

The pharmacokinetic and dynamic interactions among 3 antimalarials, ie quinine, doxycycline and mefloquine was observed in a 26-year-old Thai male patient with falciparum malaria. During the acute episode of the infection, the patient was treated with an intravenous dose of quinine hydrochloride at 600 mg qid, together with an oral dose of doxycycline 100 mg bid. Due to nausea, tinnitus and the persistence of parasitemia in peripheral blood smears, the dose of quinine was reduced 2 days after the first treatment to 300 mg; concurrently oral mefloquine 750 mg was given as 2 divided doses at 24 hours apart. During the course of treatment, the patient developed hearing loss; deafness of the right ear lasted for one week after stopping quinine administration. Higher plasma quinine and lower whole blood mefloquine concentrations than would be expected from the simulation profiles were detected 4 days after the first treatment. However, the concentration of mefloquine was increased upon the cessation of quinine treatment.