Plasma retinol and alpha-tocopherol level and growth indices of 7 months old healthy Thai infants in Bangkok.

A cross-sectional study was conducted to measure plasma retinol and alpha-tocopherol status and the growth indices of 66 healthy Thai infants aged about 7 months old. The mean (SD) plasma retinol and alpha-tocopherol level were 1.59(0.31) and 25.40(7.01) micromol/l respectively. For their weight, height, and body mass index, the mean (SD) values were 7.96(0.93) kg, 69.95(2.42) cm, and 16.25(1.43) respectively. There was a remarkable proportion of improper feeding. However there were no correlations between plasma retinol level, plasma alpha-tocopherol level, growth indices and duration of breast milk, formula milk, weaning food feeding except alpha-tocopherol level which positively correlated with duration of breastfeeding.

A new Vero cell rabies vaccine: results of a comparative trial with human diploid cell rabies vaccine in children.

We evaluated the immunogenicity and safety of a chromatographically purified rabies vaccine (CPRV) compared with human diploid cell rabies vaccine (HDCV) after pre-exposure immunizations (both primary and booster). Intramuscular doses of either 0.5 mL of CPRV or 1.0 mL of HDCV were given to 400 schoolchildren on days 0, 7, 28, and 365 (booster). Adequate titers of antibody (> or = 0.15 IU/mL, as defined by the Centers for Disease Control and Prevention) were observed in serum samples from all children 14 days after primary immunization with CPRV and HDCV; the antibodies persisted in all but one child up until 1 year. Fourteen days after the primary immunization series (day 42) and 7 days after booster immunization (day 372), all children had antibody titers of > or = 0.5 IU/mL. Local and systemic reactions after primary and booster immunizations occurred significantly less frequently in the CPRV group. A severe allergic reaction (angioedema) was reported in only one child after booster immunization with HDCV. CPRV has adequate immunogenicity for primary and booster pre-exposure immunizations in children and has a better safety profile than does HDCV.

Persistence of antibodies in children after intradermal or intramuscular administration of preexposure primary and booster immunizations with purified Vero cell rabies vaccine.

BACKGROUND: The use of intradermal (i.d.) injections of purified Vero cell rabies vaccine (PVRV) for preexposure prophylaxis has not been well-established. We studied the safety and immunogenicity of i.d. and intramuscular (i.m.) PVRV injections for primary and booster preexposure immunizations. METHODS: One of two rabies preexposure PVRV regimens comprising three doses of either 0.1 ml i.d. or 0.5 ml i.m. administered during 28 days was assigned at random to 190 school children. One booster dose was given 1 year later either i.d. or i.m., according to their initial randomization group. Serologic results were available from 155 (82%) children at 1 year after primary immunization and 118 (62%) children at 2 years after booster. RESULTS: Although children vaccinated i.d. had significantly lower rabies-neutralizing antibody titers after primary immunization as well as after booster than children vaccinated i.m. (P< 0.001 for all time points), there were no significant differences in the percentages of children with adequate titers (> or =0.15 IU/ml) between the i.d. and i.m. groups after both primary and booster immunizations. Mild local reactions were more frequent after i.d. vaccination. Mild or moderate systemic reactions were infrequent and similar after i.d. and i.m. vaccinations. Fever and headache were reported by < or =6%. The reactions after booster were not different from those of post-primary immunization. CONCLUSIONS: Purified Vero cell rabies vaccine appears to be safe and immunogenic for primary and booster preexposure immunizations. An i.d. PVRV preexposure regimen should be useful especially for rabies-endemic countries with low per capita income.

Evaluation of the safety, immunogenicity, and pharmacokinetic profile of a new, highly purified, heat-treated equine rabies immunoglobulin, administered either alone or in association with a purified, Vero-cell rabies vaccine.

A clinical evaluation of a new, purified, heat-treated equine rabies immunoglobulin (PHT-Erig), F(ab')2 preparation, was carried out in Thailand and in the Philippines-two countries where rabies is endemic. An initial prospective, randomised, controlled trial (Study 1), compared the safety and pharmacokinetics (serum concentrations of rabies antibodies) after administration either of PHT-Erig or of a commercially-available, equine rabies immune globulin (Erig PMC). A second trial (Study 2) simulated post-exposure rabies prophylaxis by using a reference cell culture vaccine, the purified Vero-cell rabies vaccine (PVRV), administered in association with either Erig PMC or PHT-Erig. In Study 1, 27 healthy, Thai adults received a 40 IU kg(-1) dose of either Erig PMC (n = 12) or PHT-Erig (n = 15) via the intramuscular (i.m.) route; half of the dose was injected into the deltoid area and the other half into the buttocks. Serum for rabies antibody determination and F(ab')2 concentration was collected at hours (H) 0, 6 and 12, and on day (D) 2, 3, 4, 6, 8, 10, 12 and 15. Both products were safe, with no serious adverse events, and in particular, no anaphylactic reactions or serum sickness was reported. A statistical comparison of the pharmacokinetic parameters did not demonstrate bioequivalence of the two products. Nonetheless, the relative bioavailability of 93% and the similar absorption rates suggest the pharmacokinetic profiles of Erig and PHT-Erig are similar. The antibody level in either group were low throughout the 15-day study period. The geometric mean titer (GMT) values ranged from group 0.027-0.117 IU ml(-1) in the Erig group and from 0.029 to 0.072 IU ml(-1) in the PHT-Erig. There was no significant difference between the evolution of GMT values for the two groups. In Study 2, 71 healthy volunteers received 40 IU kg(-1) via the intramuscular route of either Erig PMC (n = 36) or PHT-Erig (n = 35) on D0, in association with five doses of PVRV on D0, D3, D7, D14 and D28. The safety evaluation was performed during the 28-day follow-up and serum samples for anti-rabies antibody titration were collected on D0 (before injection) D3, D7, D14 and D28. No serious reactions were reported in either group. In particular, no immediate (anaphylactic type) or delayed (serum sickness) allergic reactions were observed. Over the 28-day follow-up period, GMT profiles of the two groups were statistically equivalent. On D14, 100% of the subjects had protective antibody titers (anti-rabies antibodies > or = 0.5 IU ml(-1), which is the WHO-recommended level of seroconversion), and Erig PMC and PHT-Erig were indistinguishable according to the clinical definition chosen. On D28, the GMT values were 33.2 IU ml(-1) (95% CI, 23.8-46.1 IU ml(-1)) in the Erig PMC/PVRV group and 31.4 IU ml(-1) (95% confidence interval, CI, 23.4-42.2 IU ml(-1)) in the PHT-Erig/PVRV group, showing evidence of adequate vaccine-induced antibody responses in both groups. The increased purity, the heat-treatment step introduced in the manufacturing process of PHT-Erig, and the good clinical results substantiate the use of this new generation, purified equine F(ab')2 preparation in the post-exposure prophylaxis of rabies.

Efficacy and pharmacokinetics of atovaquone and proguanil in children with multidrug-resistant Plasmodium falciparum malaria.

A trial was conducted in 32 Thai children with uncomplicated multidrug-resistant falciparum malaria to assess the efficacy, safety and pharmacokinetics of atovaquone and proguanil; plasma concentrations of atovaquone, proguanil and its metabolite, cycloguanil, were measured in a subset of 9 children. The children received atovaquone (17 mg/kg/d for 3 d) plus proguanil (7 mg/kg/d for 3 d). Twenty-six children who had only Plasmodium falciparum infection and remained in hospital for 28 d were assessed for drug efficacy. The combination regimen produced a cure rate of 100%. Parasite and fever clearance times were 47 h (range 8-75) and 50 h (range 7-111), respectively. Atovaquone and proguanil were rapidly absorbed, with median time to peak concentrations of 6 h (range 6-24) and 6 h (range 6-12), respectively. Peak concentrations of cycloguanil were achieved between 6 and 12 h (median 6) after administration of proguanil. Mean peak plasma concentration of atovaquone on day 3 was 5.1 micrograms/mL (SD = 2.1). The day 3 mean peak plasma concentration of proguanil was 306 ng/mL (SD = 108) compared with 44.3 ng/mL (SD = 27.3) for cycloguanil. Mean values for the AUC (area under plasma concentration-time curve) were 161.8 micrograms/mL.h (SD = 126.9) for atovaquone, 4646 ng/mL.h (SD = 1226) for proguanil, and 787 ng/mL.h (SD = 397) for cycloguanil. Terminal elimination half-lives of atovaquone, proguanil and cycloguanil were estimated as 31.8 h (SD = 8.9), 14.9 h (SD = 3.3) and 14.6 h (SD = 2.6), respectively. No major adverse effect was attributable to the study drugs. Atovaquone/proguanil combination is safe and highly effective, and should be especially valuable for treatment of multidrug-resistant falciparum malaria.

Comparative clinical trial of artesunate suppositories and oral artesunate in combination with mefloquine in the treatment of children with acute falciparum malaria.

A randomized pilot study to compare the safety and efficacy of artesunate suppositories (15 mg/kg/day for three days) versus oral artesunate (6 mg/kg/day for three days), both in combination with mefloquine (25 mg/kg), was conducted in 52 Thai children with uncomplicated multidrug-resistant falciparum malaria. Forty-five patients (87%) had a full 28-day follow-up in the hospital to assess efficacy and exclude reinfection. Mean [range] times to fever clearance of the two groups were similar (42 hr [15-104] versus 42 hr [6-119]). Artesunate suppositories resulted in significantly longer times to achieve 50% and 90% reductions of the initial parasite counts (17 and 26 hr versus 9 and 15 hr; P < 0.05 and P < 0.001). Time [range] to parasite clearance was longer in the artesunate suppositories group (42 hr [14-93] versus 35 hr [16-69]), but the difference was not significant. The cure rates by days 28 were not significantly different, 92% for artesunate suppository-treated patients and 100% for oral artesunate-treated patients. Both drug regimens are safe and effective. Further studies are needed to characterize the pharmacokinetic properties and the optimum regimen of artesunate suppositories for the treatment of severe malaria.

Stereoselective pharmacokinetics of mefloquine in young children.

OBJECTIVE: the stereospecificity of mefloquine pharmacokinetics in children has been investigated. PATIENTS: Twelve children aged 6 to 24 months were treated for uncomplicated falciparum malaria with a single oral dose of 25 mg.kg-1 racemic mefloquine in combination with sulfadoxine and pyrimethamine. METHODS: concentrations of mefloquine enantiomers were determined using a coupled achiral-chiral chromatographic system. Pharmacokinetic parameters were calculated using model-independent analysis. RESULTS: Maximum plasma concentrations, areas under the curve and apparent plasma elimination half-lives were higher for the (-) enantiomer than its antipode. In contrast, the apparent volume of distribution (V/f) and total clearance (Cl/f) values were higher for the (+) enantiomer. CONCLUSION: the stereoselectivity of mefloquine pharmacokinetics is similar to that observed in adults.

Pharmacokinetic study of mefloquine in Thai children aged 5-12 years suffering from uncomplicated falciparum malaria treated with MSP or MSP plus primaquine.

A triple combination of mefloquine, sulfadoxine and pyrimethamine (MSP) was used with primaquine for the radical treatment of falciparum malaria in Thailand. Primaquine was reported to inhibit hepatic microsomal enzymes and drug metabolism in animal and man. 23 children hospitalized in the Hospital for Tropical Diseases, Faculty of Tropical Medicine, Bangkok, Thailand, were randomly allocated into two groups, group I received MSP equivalent to 20 mg base of mefloquine/kg body weight and group II received MSP plus primaquine (0.75 mg/kg). No statistical difference was noted for clinical response except the gametocyte clearance time was shorter in children given MSP plus primaquine (7 +/- 2.7 days) than the children given MSP alone (21.9 +/- 4.4 days) (P < 0.01). No serious side effects were recorded in this study. The plasma samples were obtained for kinetic calculations by HPLC in 18 children (11 in group I, 7 in group II). Mean Cmax was 7.4 +/- 5.2 h in group I and 6.6 +/- 7.0 h in group II. Mean t1/2, Cl/f and Vd/f were 9.8 +/- 1.6 days, 0.43 +/- 0.16 ml/min/kg and 8.84 +/- 4.21 l/kg in group I, 9.3 +/- 1.4 days, 0.41 +/- 0.12 ml/min/kg and 8.91 +/- 3.00 l/kg group II, respectively. The comparison of kinetic parameters in groups I and II revealed no significant difference (P > 0.05) suggesting no drug interaction. These kinetic values in children given MSP suspension were considerably different to those in adult patients with shorter tmax, t1/2 and MRT. The coadministration of MSP and primaquine in children would benefit by reducing the transmission of malaria in endemic areas.

Maternal practices and risk factors for dehydration from diarrhoea in young children: a case-control study in central Thailand slums.

To determine factors related to dehydration from diarrhoea, we conducted a hospital-based, case-control study in children aged 24 months or younger who had acute watery diarrhoea and attended Chonburi Regional Hospital in central Thailand during November 1988 through May 1989. The study compared 48 cases who had moderate or severe dehydration with 48 controls who had no dehydration. Both cases and controls belonged to low socioeconomic families and were living in urban slum areas. They had adequate health care facilities and access to ORS packets. Overall, 56% of the mothers used ORS solution at home. None of the mothers knew how to administer ORS, i.e. the fluid was not given at the onset of diarrhoea to prevent dehydration, and they gave no more than 60 ml over a 24-hour period to their dehydrated children. They also did not use home fluids. Multivariate analysis of data showed two factors significantly associated with dehydration: children's dirty fingernails that indicated inadequate maternal hygiene-related behaviour (Odds Ratio 6.4; 95% Confidence Intervals 1.5-27.6, p < 0.01), and frequency of vomiting in the 24 hours before rehydration (Odds Ratio 1.3; 95% Confidence Intervals 1.1-1.6, p < 0.001). Cases and controls had similar aetiologic agents and nutritional status. Providing proper education to mothers about oral rehydration therapy with special emphasis on the volume of ORS to be given, along with guidance to improve their personal hygiene should be considered important interventions in reducing the risk of dehydration and deaths from diarrhoea in these children.

Pharmacokinetics of mefloquine in children aged 6 to 24 months.

The study was carried out in 12 children aged 6 months to 2 years, with uncomplicated falciparum malaria admitted to the Hospital for Tropical Diseases, Bangkok. They were treated with mefloquine in the form of MSP (mefloquine 250 mg+sulfadoxine 500 mg+pyrimethamine 25 mg) at a single dose of 25 mg mefloquine base/kg body weight. All of them were cured (28 days follow-up) with minimal side effects. Pharmacokinetic parameter determination was carried out in 9 cases. The results revealed that MRT, t1/2 and tmax in this study (children 6-24 months old) are comparable to the values in children aged 5-12 years, but shorter than in adult patients. Cmax and AUC in children 6-24 months old are comparable to those in children of 5-12 years, but much higher than in adult patients. Vz/f values in this study are comparable to those in children 5-12 years old, but lower than in adult patients.

Pharmacokinetics of primaquine in healthy volunteers.

The pharmacokinetics of primaquine were investigated in 8 healthy subjects (4 males and 4 females). The volunteers received 15 mg base of primaquine daily for 14 days. The results showed that the concentration-time profiles in whole blood and in plasma were similar. The mean values (+/- SD) of area under the curve (AUC) of the last dose were significantly decreased when compared to the values of the first dose both in whole blood and in plasma (909.96 +/- 603.07, 1,147.05 +/- 684.8 ng.hr/ml respectively in whole blood with p = 0.007 and 1,255.11 +/- 531.59, 1,603.66 +/- 505.45 ng.hr/ml respectively in plasma with p = 0.023). The decrease in the concentration-time profile of the last dose was due to enhancement of drug elimination with significant increase in clearance after the last dose (4.871 +/- 1.741 and 6.443 +/- 2.514 ml/min/kg respectively in whole blood with p = 0.007, 3.199 +/- 1.197 and 4.422 +/- 2.068 ml/min/kg respectively in plasma with p = 0.016).

Parasitologic and clinical human response to immunoglobulin administration in falciparum malaria.

The protective effect of African IgG antibodies against Plasmodium falciparum malaria was investigated by passive transfer in Thai patients. Sera from 333 African adults were collected in the Cote d'Ivoire and subjected to extensive screening. One hundred fifty-three samples were discarded for safety reasons, and IgG was extracted from those remaining under conditions allowing their use by the intravenous (iv) route. Eight Thai patients with P. falciparum parasitemia were treated by iv inoculation of the IgG: six with a 100 mg/kg dose given over three days, one with a single 20 mg/kg dose, and one with a single 200 mg/kg dose. To ensure a safety margin of at least 48 hours, subjects were chosen among patients having a recrudescent parasitemia following quinine treatment failure at the RI level. At that stage, symptoms were mild or absent and parasitemia was low but increasing (range 4, 200-9,000/microliters). The IgG pool exerted a profound, stage-specific, but non-sterilizing effect on each of the strains tested, and proved to be safe. Asexual parasitemia decreased by a mean 728-fold (range 46-1,086), while gametocytes were unaffected. Clearance of parasites and symptoms was as fast or faster than with drugs, and was consistent in the eight patients treated, suggesting that target antigens were equally expressed in geographically remote isolates. In peripheral blood smears, no mature forms were seen at any time during the followup, which does not support the hypothesis that reversal of cytoadherence occurred. After the disappearance of the transferred antibodies, recrudescent parasites from three patients were found to be susceptible to the same extent (mean decrease of 1,310-fold) to the same IgG preparation, indicating that selection of parasites able to escape the effect of antibodies had not occurred. No adverse side-effects were detected during the followup, which lasted one year.

Red cell and plasma concentrations of combined quinine-quinidine and quinine in falciparum malaria.

Red cell and plasma quinine-quinidine, and quinine concentrations in children with uncomplicated falciparum malaria who were treated with a combination of quinine/quinidine/cinchonine (combined drug) and quinine alone, respectively, were measured, using the extraction fluorescence method. The cure rates obtained with the high dose regimen of the combined drug (100%) were significantly higher than in the low dose regimen group (37.5%) (p less than 0.05), and the quinine regimen produced a 50% cure rate. Similar mild and transient ECG effects were noted in both the combined drug group and the quinine group. In patients treated with the combined drug, quinine-quinidine concentrations in both red cell and plasma of the high dose regimen group were significantly higher than those in the low dose regimen group (p less than 0.001, p less than 0.001). In quinine-treated patients, red cell quinine concentration in those with RII failure was significantly lower than that in patients with cure or RI failure (p less than 0.05). Both red cell and plasma levels of quinine-quinidine were higher than quinine levels. The red cell:plasma quinine-quinidine concentration ratios rose steadily to the high level from day 3 to day 6, while the ratio of quinine alone fluctuated around the low level and then gradually fell. The evidence suggests that red cell drug concentrations are more closely related to the outcome of treatment than to plasma concentrations and that the combined drug may be very useful for treatment of multi-drug-resistant P. falciparum infections. Further study is needed.

Antibodies that protect humans against Plasmodium falciparum blood stages do not on their own inhibit parasite growth and invasion in vitro, but act in cooperation with monocytes.

IgG extracted from the sera of African adults immune to malaria were injected intravenously into eight Plasmodium falciparum-infected nonimmune Thai patients. Clinical and parasitological improvement was reproducibly obtained in each case. After the disappearance of the transferred Ig, recrudescent parasites were equally susceptible to the same Ig preparation. High levels of antibodies to most parasite proteins were detected by Western blots in the receivers' sera (taken before transfer) as in the donors' Ig, thus indicating that the difference was qualitative rather than quantitative between donors and receivers. In vitro, the clinically effective Ig had no detectable inhibitory effect on either penetration or intra-erythrocytic development of the parasite. On the contrary, they sometimes increased parasite growth. In contrast, these IgG, as the receivers' Ig collected 4 d after transfer, but not those collected before transfer, proved able to exert an antibody-dependent cellular inhibitory (ADCI) effect in cooperation with normal blood monocytes. Results were consistent among the seven isolates studied in vitro, as with the recrudescent parasites. Thus, the results obtained in the ADCI assay correlate closely with clinical and parasitological observations.

In vivo and in vitro responses to quinine and quinidine of Plasmodium falciparum.

A total of 66 Thai children with uncomplicated falciparum malaria were treated orally with regimens of either quinine or quinidine. Radical cures were observed in 85% (28 of 33) of the children who received quinine and in 88% (29 out of 33) of those who received quinidine. Treatment failures in both groups were RI responses.The mean trough level of quinidine (10 mumol/l) was about 2.5-times less than that of quinine (25 mumol/l). The electrocardiograms of the two treatment groups differed significantly in that there was an acute prolongation of the QT(c) interval in 56% of those who received quinidine compared with 21.0% of those given quinine. In vitro assays of the pretreatment drug susceptibilities of the isolates of Plasmodium falciparum indicated that the mean minimum inhibitory concentration (MIC) for quinidine (1.44 mumol/l) was about half that for quinine (3.02 mumol/l). Although both drugs are equally effective, quinine is recommended for treatment of multidrug-resistant malaria in paediatric patients, primarily because of the cardiac effects produced by quinidine.

A phase-III clinical trial of mefloquine in children with chloroquine-resistant falciparum malaria in Thailand.

Mefloquine is a highly effective drug for the treatment of falciparum malaria among adults, but studies of its effects on children are lacking. An open, noncomparative trial of mefloquine was therefore carried out among 84 children aged 5-12 years who were patients at the Hospital for Tropical Diseases, Mahidol University, Bangkok, Thailand. The drug was administered as a single dose of 18-29 mg base per kg body weight. Eighty-two of the 84 children completed a 42-day period of post-treatment observation. The drug was well tolerated also by 11 children with glucose-6-phosphate dehydrogenase deficiency, and all the children in the study cleared their parasitaemia initially (average clearance time, 65 hours). Furthermore, the clinical-chemical parameters measured exhibited no drug-related changes during the study. The radical cure rate of nearly 98% and high tolerance indicate that mefloquine can be used effectively and safely for the treatment of children aged 5-12 years who are suffering from uncomplicated falciparum malaria.

Evaluation of an in vitro test method for the assessment of sensitivity of Plasmodium falciparum to pyrimethamine and sulfadoxine.

Twenty three Plasmodium falciparum isolates collected from two highly pyrimethamine/sulfadoxine-resistant areas of Thailand were evaluated for their in vitro responses to pyrimethamine, sulfadoxine and combinations of these two drugs in various conditions. The test procedure was based on inhibition of parasite multiplication and of schizont formation, using the recommended modified RPMI medium 1640 with PABA 0.5 mug per litre and folic acid 10 mug per litre (LPLF). The optimum blood/medium ratios and inoculum sizes for parasite multiplication and for schizont formation were 1:19, 100 mul/well and 1:9, 50 mul/well, respectively. The appropriate incubation period was 48 hours. It was found that inhibition of either parasite multiplication or schizont formation could be used as the endpoint for evaluating the antiplasmodial action of pyrimethamine and combined pyrimethamine/sulfadoxine in vitro for field investigations; however, inhibition of only parasite multiplication should be used for determination of sulfadoxine activity. The actions of pyrimethamine in the combination pyrimethamine/sulfadoxine in ratios of 1:80 and 1:200 were similar. In vitro testing using combined pyrimethamine/sulfadoxine should be more precise than pyrimethamine alone for monitoring parasite susceptibility to the combined drug (Fansidar).