Sirivan Vanijanonta

Therapeutic Responses to Different Antimalarial Drugs in Vivax Malaria

ABSTRACT The therapeutic responses to the eight most widely used antimalarial drugs were assessed in 207 adult patients withPlasmodium vivax malaria. This parasite does not cause marked sequestration, so parasite clearance can be used as a direct measure of antimalarial activity. The activities of these drugs in descending order were artesunate, artemether, chloroquine, mefloquine, quinine, halofantrine, primaquine, and pyrimethamine-sulfadoxine (PS). Therapeutic responses to PS were poor; parasitemias did not clear in 5 of the 12 PS-treated patients, whereas all the other patients made an initial recovery. Of 166 patients monitored for ≥28 days, 35% had reappearance of vivax malaria 11 to 65 days later and 7% developed falciparum malaria 5 to 21 days after the start of treatment. There were no significant differences in the times taken for vivax malaria reappearance among the different groups except for those given mefloquine and chloroquine, in which all vivax malaria reappearances developed >28 days after treatment, suggesting suppression of the first relapse by these slowly eliminated drugs. There was no evidence of chloroquine resistance. The antimalarial drugs vary considerably in their intrinsic activities and stage specificities of action.

Quinine in severe falciparum malaria: evidence of declining efficacy in Thailand

Between 1981 and 1992, 196 Thai adults with severe falciparum malaria were treated with a quinine loading dose regimen. Nineteen patients died (10%) and 6 developed late hypoglycaemia. There was no serious cardiovascular or nervous system toxicity. Although there was no evidence of high grade resistance, and no change in the mortality rate, in recent years an increasing proportion of patients had a delayed clinical and parasitological response to treatment. Since 1988, 78% (29/37) of patients with cerebral malaria were unconscious for > 72 h compared with 41% (11/27) between 1981 and 1987 (P = 0.002). In the past 2 years parasite clearance times have exceeded 96 h in 33% (26/78) of patients compared with 14% (15/102) previously (P = 0.006). Quinine remains an effective treatment for severe multi-drug resistant falciparum malaria in this area, but there is now evidence of a decline in the immediate therapeutic response, and its efficacy will need close monitoring as resistance increases further.

Therapeutic Responses to Quinine and Clindamycin in Multidrug-Resistant Falciparum Malaria

ABSTRACT Therapeutic responses to clindamycin in combination with quinine were assessed in adult Thai patients with uncomplicated multidrug-resistant Plasmodium falciparum malaria. In total 204 patients were randomized to receive a 7-day oral treatment regimen of quinine (Q7) either alone (n = 68), in combination with clindamycin (Q7C7;n = 68), or in combination with tetracycline (Q7T7; n = 68). All patients had uncomplicated recoveries with no serious adverse effects. Fever clearance times for both of the two combination regimens (median of 47 h and range of 8 to 120 h for Q7C7and median of 36 h and range of 8 to 117 h for Q7T7) were significantly shorter than that for the Q7-only regimen (median, 56; range, 4 to 152 h) (P = 0.002). Parasite clearance times (overall mean ± standard deviation, 78 ± 23 h) were not significantly different between the three treatment groups (P = 0.98). The cure rates assessed at 28 days of follow-up were 100% for Q7C7 and 98% for Q7T7, whereas the cure rate was 87% for the Q7-only regimen (P ≤ 0.04). Clindamycin in combination with quinine is a safe and effective treatment for multidrug-resistant P. falciparum malaria. This combination may be of particular value in children and pregnant women, in whom tetracyclines are contraindicated.

Safety and Reactogenicity of Canarypox ALVAC-HIV (vCP1521) and HIV-1 gp120 AIDSVAX B/E Vaccination in an Efficacy Trial in Thailand

Background A prime-boost vaccination regimen with ALVAC-HIV (vCP1521) administered intramuscularly at 0, 4, 12, and 24 weeks and gp120 AIDSVAX B/E at 12 and 24 weeks demonstrated modest efficacy of 31.2% for prevention of HIV acquisition in HIV-uninfected adults participating in a community-based efficacy trial in Thailand. Methodology/Principal Findings Reactogenicity was recorded for 3 days following vaccination. Adverse events were monitored every 6 months for 3.5 years, during which pregnancy outcomes were recorded. Of the 16,402 volunteers, 69% of the participants reported an adverse event any time after the first dose. Only 32.9% experienced an AE within 30 days following any vaccination. Overall adverse event rates and attribution of relatedness did not differ between groups. The frequency of serious adverse events was similar in vaccine (14.3%) and placebo (14.9%) recipients (p = 0.33). None of the 160 deaths (85 in vaccine and 75 in placebo recipients, p = 0.43) was assessed as related to vaccine. The most common cause of death was trauma or traffic accident. Approximately 30% of female participants reported a pregnancy during the study. Abnormal pregnancy outcomes were experienced in 17.1% of vaccine and 14.6% (p = 0.13) of placebo recipients. When the conception occurred within 3 months (estimated) of a vaccination, the majority of these abnormal outcomes were spontaneous or elective abortions among 22.2% and 15.3% of vaccine and placebo pregnant recipients, respectively (p = 0.08). Local reactions occurred in 88.0% of vaccine and 61.0% of placebo recipients (p<0.001) and were more frequent after ALVAC-HIV than AIDSVAX B/E vaccination. Systemic reactions were more frequent in vaccine than placebo recipients (77.2% vs. 59.8%, p<0.001). Local and systemic reactions were mostly mild to moderate, resolving within 3 days. Conclusions/Significance The ALVAC-HIV and AIDSVAX B/E vaccine regimen was found to be safe, well tolerated and suitable for potential large-scale use in Thailand. Trial Registration ClinicalTrials.gov NCT00223080

Efficacy and tolerability of a sequential, artesunate suppository plus mefloquine, treatment of severe falciparum malaria.

Thirty patients with severe falciparum malaria were each given a total of 1600-mg artesunate suppository over three consecutive days followed by 1250 mg mefloquine per os, divided into two doses which were given 12 h apart. All patients were admitted for 28 days to the Bangkok Hospital for Tropical Diseases, so that the efficacy and tolerability of the treatment could be assessed. All the patients showed clinical improvement, with mean (S.D.) parasite and fever clearance times of 50.4 (13.0) and 70.7 (44.9) h, respectively. Two patients with unrousable coma (Glasgow coma score < or = 8) on admittance regained consciousness 46 and 48 h post-treatment. One other patient had acute renal failure and required dialysis. Most patients (80%) were initially hyperparasitaemic, with a mean density of 184,344 parasites/microliters blood. No deaths occurred. Efficacy was evaluated in 25 of the patients. The cure rate 28 days post-treatment was 92%. None of the patients had major adverse effects although two had tenesmus and passed stools immediately after each suppository was administered. A fresh suppository had to be inserted when this occurred. The results indicate that artesunate suppositories followed by oral mefloquine constitute a well-tolerated regimen with a high cure rate. The combination is suitable as an alternative treatment for severe malaria, particularly in children. Further, large-scale studies are required.

Treatment of acute, uncomplicated, falciparum malaria with oral dihydroartemisinin

A clinical trial of oral dihydroartemisinin for the treatment of acute, uncomplicated, falciparum malaria involved 53 adult patients in Thailand. Each received a total dose of 480 mg over 7 days (120 mg given immediately, followed by 60 mg/day) after being admitted to the Hospital for Tropical Diseases in Bangkok for 28 days. Most (92%) completed the 28-day follow-up but four patients left the hospital early, for reasons unrelated to their treatment. Most patients showed clinical improvement 1-3 days after starting treatment and none suffered from serious adverse reactions. The cure rate was 90% (44/49). The mean (S.D.) parasite-clearance time was 40.4 (14.1) h and the mean fever-clearance time was 37.0 (30.2) h. Seven patients had a brief increase in parasitaemia after initiation of treatment but subsequent counts declined dramatically. Five patients who failed treatment (RI response) were successfully treated with quinine plus tetracycline for 7 days. No RII or RIII responses were observed. These findings indicate that treatment with oral dihydroartemisinin is effective and well tolerated, and that dihydroartemisinin may be suitable as an alternative treatment for acute, uncomplicated, falciparum malaria. Comparisons with other conventional antimalarial drugs in a large, double-blind, randomized trial and studies of dihydroartemisinin in combination with other, long-acting antimalarials are needed.

Randomised trial of mefloquine-tetracycline and quinine-tetracycline for acute uncomplicated falciparum malaria

The combination of mefloquine plus tetracycline was compared with quinine plus tetracycline in a randomised therapeutic trial in 102 patients with acute uncomplicated falciparum malaria in Thailand. Quinine plus tetracycline is considered the standard treatment for the highly drug-resistant strains of P. falciparum found in this area. Fifty patients received mefloquine (750 mg given immediately, followed by 500 mg 6 h later) with tetracycline and 52 patients received quinine (600 mg every 8 h for seven days) with tetracycline. Tetracycline was administered to both groups in doses of 250 mg four times daily. All patients were admitted to the hospital for 28 days to exclude re-infection. Ninety-three patients completed the study; nine patients left prior to completion of follow-up for reasons unrelated to their treatment. Cure rates for the two groups were 94% (44/47) for mefloquine plus tetracycline and 98% (45/46) for quinine plus tetracycline. Parasite and fever clearance times were shorter for the group treated with mefloquine but the differences were not statistically significant. Nearly all patients (94%) treated with quinine developed cinchonism compared with only 12% treated with mefloquine; all other symptoms following treatment were similar. Thirteen patients (26%) treated with quinine also developed delayed primary attacks of P. vivax during the follow-up period; none developed in the patients treated with mefloquine. These results support the contention that the combination of mefloquine plus tetracycline is equally effective and less toxic than quinine plus tetracycline for treatment of acute uncomplicated falciparum malaria in areas requiring combination therapy for drug resistance.

Monotherapy with sodium artesunate for uncomplicated falciparum malaria in Thailand: a comparison of 5- and 7-day regimens

We compared the safety and efficacy of two treatment regimens using sodium artesunate in 91 randomized patients with uncomplicated falciparum malaria acquired in Thailand. One group of 45 patients received 400 mg of artesunate on the first day of treatment and then 200 mg daily for 4 days for a total of 1200 mg (group I: 5-day treatment). A second group of 46 patients received 400 mg of artesunate on the first day of treatment and then 200 mg daily for 6 days for a total of 1600 mg (group II: 7-day treatment). Both regimens were well tolerated. All patients were followed for a total of 28 days. By the third day of treatment, most patients were blood smear negative for parasites. Eighty-two patients completed the 28-day follow-up period and were used for describing the cure rate. All patients treated with the 5-day regimen were cured. In the 7-day treatment group, 98% (39 of 40) of the patients were cured; one patient developed late recrudescence (RI). There were no significant differences in fever clearance or parasite clearance between the two groups. However, 13 patients (five in group I and eight in group II) developed Plasmodium vivax infection during the follow-up period. We conclude that 5- or 7-day regimens of sodium artesunate with a total dose of 1200-1600 mg are effective and safe in treating falciparum malaria acquired in Thailand.

Hepatic metabolism in severe falciparum malaria: caffeine clearance study.

Falciparum malaria is known to cause abnormalities in the liver. Hepatic metabolism in patients with falciparum was studied by caffeine clearance and the results were related to the severity of the disease. Caffeine (3.5 mg/kg) was administered orally to patients with severe (N = 10) or uncomplicated (N = 9) falciparum malaria. The plasma clearances during illness averaged 0.67 +/- 0.27 ml/min kg for the severe cases and 0.98 +/- 0.36 ml/min kg for the uncomplicated cases (P < 0.05). In the severe patients, clearances during illness (0.67 +/- 0.27 ml/min kg) were less than those in convalescence (2.15 +/- 0.91 ml/min kg) (P < 0.0001). However, in the uncomplicated cases, the clearances during illness and in convalescence were similar (P > 0.05) and clearance rates in convalescence were similar for the severe and uncomplicated cases (P > 0.05). Hepatic microsomal metabolism is apparently slow in severe falciparum malaria but reverts to normal in convalescence. Liver metabolic function does not appear to be significantly affected in uncomplicated malaria.

Therapeutic effects of antivenom supplemented by antithrombin III in rats experimentally envenomated with Russell's viper (Daboia russelli siamensis) venom

The effects of equine antivenom and antithrombin III (AT-III) on the coagulopathy induced by Russells viper venom (RVV, Daboia russelli siamensis) were investigated in the rat. After taking blood samples from the femoral vein for determination of simple blood clotting time and AT-III activity, all anaesthetized rats received an intramuscular injection of venom (2 micrograms/g). Treatment (antivenom or AT-III or both) was given intravenously through another femoral vein 30 min after venom injection. All untreated rats (n = 7) developed AT-III depletion (< 70%) [mean (S.D.)] 70 (36) min, and incoagulable blood 85 (53) min after venom injection. Supplementation with AT-III (either 0.25 U/g or 0.5 U/g) had no effect on the RVV induced coagulopathy (n = 20). Treatment with antivenom alone (10 micrograms/g) reduced the incidence of abnormal clotting significantly (8/15, 53%) (P = 0.03). When antivenom was given in combination with AT-III (0.5 U/g), abnormal clotting was prevented in all but one animal (1/15, 7%) (P = 0.007). AT-III activity declined progressively in all rats which developed non-clotting blood. These results suggest that coagulopathy in Russells viper envenoming is associated with activation of coagulation and consumption of AT-III. Antivenom can prevent coagulopathy, but its neutralizing activity is augmented significantly by AT-III supplementation.