Sensitivity of Plasmodium falciparum to antimalarial drugs in Hainan Island, China.

Pyronaridine and artesunate have been shown to be effective in falciparum malaria treatment. However, pyronaridine is rarely used in Hainan Island clinically, and artesunate is not widely used as a therapeutic agent. Instead, conventional antimalarial drugs, chloroquine and piperaquine, are used, explaining the emergence of chloroquine-resistant Plasmodium falciparum. In this article, we investigated the sensitivity of P. falciparum to antimalarial drugs used in Hainan Island for rational drug therapy. We performed in vivo (28 days) and in vitro tests to determine the sensitivity of P. falciparum to antimalarial drugs. Total 46 patients with falciparum malaria were treated with dihydroartemisinin/piperaquine phosphate (DUO-COTECXIN) and followed up for 28 day. The cure rate was 97.8%. The mean fever clearance time (22.5 ± 10.6 hr) and the mean parasite clearance time (27.3 ± 12.2 hr) showed no statistical significance with different genders, ages, temperatures, or parasite density (P > 0.05). The resistance rates of chloroquine, piperaquine, pyronarididine, and artesunate detected in vitro were 71.9%, 40.6%, 12.5%, and 0%, respectively (P < 0.0001). The resistance intensities decreased as follows: chloroquine > piperaquine > pyronarididine > artesunate. The inhibitory dose 50 (IC50) was 3.77 × 10(-6) mol/L, 2.09 × 10(-6) mol/L, 0.09 × 10(-6) mol/L, and 0.05 × 10(-6) mol/L, and the mean concentrations for complete inhibition (CIMC) of schizont formation were 5.60 × 10(-6) mol/L, 9.26 × 10(-6) mol/L, 0.55 × 10(-6) mol/L, and 0.07 × 10(-6) mol/L, respectively. Dihydroartemisinin showed a strong therapeutic effect against falciparum malaria with a low toxicity.

[Efficacy of dihydroartemisinin-piperaquine and artemether-lumefantrine in the treatment of uncomplicated falciparum malaria in Hainan, China].

OBJECTIVE: To assess the therapeutic efficacy of the combinations dihydroartemisinin-piperaquine and artemether-lumefantrine in treating uncomplicated falciparum malaria cases in an area with high level resistance of Plasmodium falciparum to chloroquine in Hainan Province. METHODS: Patients aged 1 to 60 with uncomplicated P. falciparum infection and parasite density 1,000 to 200,000 parasites/microl were enrolled following an informed consent. Eligible patients were randomly assigned to 2 groups for receiving either a 3-day course of dihydroartemisinin-piperaquine (40/320 mg, DP, group A) or 6-dose course of artemether/lumefantrine (20/120 mg tablets, AL, group B) over three days. They were followed up with clinical and laboratory examinations until day 28 using standard WHO in vivo antimalarial drug test protocol. RESULTS: Altogether 107 eligible patients were enrolled but 106 completed the study. Adequate clinical and parasitological response (ACPR) was observed in 51 (100%) and 55 (100%) cases in groups A and B respectively. The mean time of fever clearance and mean time of asexual parasite clearance were (20.99 +/- 11.38) h and (36.45 +/- 12.60) h in AL and (22.35 +/- 13.26)h and (34.99 +/- 12.28) h in DP, respectively. There was no statistical difference on the mean time of fever clearance and asexual parasite clearance between AL and DP (P > 0.05). None of the participants showed recrudescence and serious adverse effect. CONCLUSION: Both combinations artemether-lumefantrine and dihydroartemisinin-piperaquine show a high cure rate and proper tolerability among the patients with uncomplicated falciparum malaria in Hainan.

[Study on the haplotypes of pfcrt polymorphism from Hainan Province].

OBJECTIVE: To develop a method for comparing the haplotypes of pfcrt polymorphism of Hainan Province with those from other areas of the world. METHODS: Nested PCR was used to amplify the polymorphic region including codon 72 to 76 and 97 of pfcrt gene. The PCR products were digested by ApoI restriction endonuclease to determine the allelic types. According to the allelic types, 6 products from each of mutant type and wild type were sequenced to analyze the haplotypes of pfcrt polymorphism. RESULTS: Bands in size of 195 bp appeared in all 19 samples. After ApoI digestion, 11 samples contained one ApoI site when codon 76 of the pfcrt gene codes for lysine (K76), which were visualized by the presence of 98 bp and 97 bp restriction fragments. The DNA sequencing revealed that 6 samples of chloroquine resistant P. falciparum carried pfcrt alleles encoding an amino acid haplotype of CVIET (residues 72-76), and the haplotype of CVMNK was found in other 6 samples with wild type pfcrt gene. CONCLUSION: Haplotypes of pfcrt polymorphism from Hainan were the same as those from southeast Asia and Africa.

[Fluctuation in the resistance of Plasmodium falciparum to chloroquine in China].

OBJECTIVE: To investigate whether chloroquine-resistance of Plasmodium falciparum had changed after stopping or reducing the use of chloroquine as an antimalarial in Hainan and Yunnan provinces. METHODS: WHO standard in vitro microtest and 4-week in vivo test were used, assays were carried out in different time after stopping or reducing the use of chloroquine. RESULTS: In vitro test in Hainan indicated that the rate of chloroquine-resistant P. falciparum was 97.9% in 1981, and dropped to 26.7% in 1997 (P<0.01). The mean concentration of chloroquine for complete inhibition of schizont formation was 10.46 +/- 7.14 pmol/microl blood in 1981, decreased to 1.63 +/- 1.47 pmol/microl blood in 1997 (P<0.01). The proportion of samples taken from malaria cases that required high concentration (>6.4 pmol/microl blood) of chloroquine for complete inhibition of schizont formation was 83.3% in 1981 and only 6.7% in 1997 (P<0.01). In the 4-week in vivo test, the rate of chloroquine-resistant P. falciparum decreased from 84.2% in 1981 to 18.4% in 1997 (P<0.01). RIII cases accounted for 53.1% of the total resistant cases in 1981, and for 14.3% in 1997 (P<0.01). In vitro test in Yunnan revealed that the rate of chloroquine-resistant P. falciparum, the mean concentration of chloroquine for complete inhibition of schizont formation and the proportion of samples taken from malaria cases that required >6.4 pmol/microl blood of chloroquine for complete inhibition of schizont formation were 97.4%, 17.2 +/- 12.6 pmol/microl blood and 58.9% in 1981 respectively, and dropped to 70.4% (P< 0.01), 4.0 +/- 3.3 pmol/microl blood (P<0.01) and 16.6% (P<0.01) in 2002 respectively. CONCLUSION: The resistance of P. falciparum to chloroquine declined progressively after its use had been stopped or reduced in Hainan and Yunnan provinces.

[Therapeutic effect of dihydroartemisinin combined with naphthoquine phosphate in patients with falciparum malaria].

OBJECTIVE: To observe the therapeutic efficacy of dihydroartemisinin combined with naphthoquine phosphate in patients with falciparum malaria. METHODS: Patients with Plasmodium falciparum were selected as the subjects, treated with a single dose of dihydroarteminisinin 160 mg combined with naphthoquine phosphate 400 mg (for adults) and followed up in preselective time by blood and temperature examination for 28 days after drug administration. RESULTS: 37 patients with falciparum malaria were treated and followed up. One patient had recrudescence and the cure rate in 28 days was 97.3%(36/37). The mean fever clearance time was (15.8 +/- 8.7) hours; the mean parasite clearance time was (27.6 +/- 13.2) hours; the mean reduction parasite rate in 24 hours was 96.7% +/- 26.5%. No apparent side effect was observed. CONCLUSION: A combination of dihydroartemisinin and naphthoquine is effective for the treatment of patients with falciparum malaria.

[Study on treatment of multi-drug resistant falciparum malaria by using a combination of dihydroartemisinin and pyronaridine].

OBJECTIVE: To provide a combined medication scheme for the treatment of multi-drug resistant falciparum malaria. METHODS: Combined administration of dihydroartemisinin and pyronaridine was given to the 32 cases of falciparum malaria cases with multi-drug resistance. The indices for evaluation on day 14, 21, and 28 after treatment included the mean fever subsidence time, mean asexual form clearance time, mean recrudescence time of asexual form and recrudescence rate, proportion of gametocyte carriers, mean density of gametocytes and its mean clearance time, cure rate and rate of side-effects. A double blind clinical test was performed with standard schemes of dihydroartemisinin (20 cases) and pyronaridine (25 cases) as control. RESULTS: The mean fever subsidence time of treated patients by dihydroartemisinin/pyronaridine combination, dihydroartemisinin and pyronaridine was 35.7 +/- 24.7 h, 52.6 +/- 38.9 h and 35.8 +/- 16.5 h respectively, showing a significant difference between the combination group and dihydroartemisinin groups (P < 0.01). The mean asexual form clearance time was 23.8 +/- 10.1 h, 22.9 +/- 6.5 h and 49.4 +/- 20.3 h respectively, showing significantly faster in the combination group than the pyronaridine group (P < 0.01). The recrudescence rate was 0, 4.2% and 0 respectively. The proportion of gametocyte carriers was 20.0%, 16.7% and 60.9% respectively, with a significantly higher rate in the group of pyronaridine than the group of combination (P < 0.01). CONCLUSION: The combination of dihydroartemsinin and pyronaridine is an ideal medication scheme for the treatment of falciparum malaria cases with multi-drug resistance.