A model for malaria treatment evaluation in the presence of multiple species

Plasmodium falciparum and P. vivax are the two most common causes of malaria. While the majority of deaths and severe morbidity are due to P. falciparum, P. vivax poses a greater challenge to eliminating malaria outside of Africa due to its ability to form latent liver stage parasites (hypnozoites), which can cause relapsing episodes within an individual patient. In areas where P. falciparum and P. vivax are co-endemic, individuals can carry parasites of both species simultaneously. These mixed infections complicate dynamics in several ways: treatment of mixed infections will simultaneously affect both species, P. falciparum can mask the detection of P. vivax, and it has been hypothesised that clearing P. falciparum may trigger a relapse of dormant P. vivax. When mixed infections are treated for only blood-stage parasites, patients are at risk of relapse infections due to P. vivax hypnozoites. We present a stochastic mathematical model that captures interactions between P. falciparum and P. vivax, and incorporates both standard schizonticidal treatment (which targets blood-stage parasites) and radical cure treatment (which additionally targets liver-stage parasites). We apply this model via a hypothetical simulation study to assess the implications of different treatment coverages of radical cure for mixed and P. vivax infections and a "unified radical cure" treatment strategy where P. falciparum, P. vivax, and mixed infections all receive radical cure after screening glucose-6-phosphate dehydrogenase (G6PD) normal. In addition, we investigated the impact of mass drug administration (MDA) of blood-stage treatment. We find that a unified radical cure strategy leads to a substantially lower incidence of malaria cases and deaths overall. MDA with schizonticidal treatment was found to decrease P. falciparum with little effect on P. vivax. We perform a univariate sensitivity analysis to highlight important model parameters.

Population pharmacokinetics of intravenous artesunate: a pooled analysis of individual data from patients with severe malaria

There are ~660,000 deaths from severe malaria each year. Intravenous artesunate (i.v. ARS) is the first-line treatment in adults and children. To optimize the dosing regimen of i.v. ARS, the largest pooled population pharmacokinetic study to date of the active metabolite dihydroartemisinin (DHA) was performed. The pooled dataset consisted of 71 adults and 195 children with severe malaria, with a mixture of sparse and rich sampling within the first 12 h after drug administration. A one-compartment model described the population pharmacokinetics of DHA adequately. Body weight had the greatest impact on DHA pharmacokinetics, resulting in lower DHA exposure for smaller children (6–10 kg) than adults. Post hoc estimates of DHA exposure were not significantly associated with parasitological outcomes. Comparable DHA exposure in smaller children and adults after i.v. ARS was achieved under a dose modification for intramuscular ARS proposed in a separate analysis of children.

A study protocol for a randomised open-label clinical trial of artesunate-mefloquine versus chloroquine in patients with non-severe Plasmodium knowlesi malaria in Sabah, Malaysia (ACT KNOW trial)

INTRODUCTION

Malaria due to Plasmodium knowlesi is reported throughout South-East Asia, and is the commonest cause of it in Malaysia. P. knowlesi replicates every 24 h and can cause severe disease and death. Current 2010 WHO Malaria Treatment Guidelines have no recommendations for the optimal treatment of non-severe knowlesi malaria. Artemisinin-combination therapies (ACT) and chloroquine have each been successfully used to treat knowlesi malaria; however, the rapidity of parasite clearance has not been prospectively compared. Malaysia's national policy for malaria pre-elimination involves mandatory hospital admission for confirmed malaria cases with discharge only after two negative blood films; use of a more rapidly acting antimalarial agent would have health cost benefits. P. knowlesi is commonly microscopically misreported as P. malariae, P. falciparum or P. vivax, with a high proportion of the latter two species being chloroquine-resistant in Malaysia. A unified ACT-treatment protocol would provide effective blood stage malaria treatment for all Plasmodium species.

METHODS AND ANALYSIS

ACT KNOW, the first randomised controlled trial ever performed in knowlesi malaria, is a two-arm open-label trial with enrolments over a 2-year period at three district sites in Sabah, powered to show a difference in proportion of patients negative for malaria by microscopy at 24 h between treatment arms (clinicaltrials.gov #NCT01708876). Enrolments started in December 2012, with completion expected by September 2014. A total sample size of 228 is required to give 90% power (α 0.05) to determine the primary end point using intention-to-treat analysis. Secondary end points include parasite clearance time, rates of recurrent infection/treatment failure to day 42, gametocyte carriage throughout follow-up and rates of anaemia at day 28, as determined by survival analysis.

ETHICS AND DISSEMINATION

This study has been approved by relevant institutional ethics committees in Malaysia and Australia. Results will be disseminated to inform knowlesi malaria treatment policy in this region through peer-reviewed publications and academic presentations.

TRIAL REGISTRATION NUMBER

NCT01708876.

Highly effective therapy for maternal malaria associated with a lower risk of vertical transmission

Background. The epidemiology of congenital malaria was investigated in a hospital-based malaria surveillance study in Papua, Indonesia.

Methods. From April 2005 to January 2010, 4878 delivering women and their newborns underwent prospective clinical review and malaria screening by peripheral blood microscopy.

Findings. Congenital malaria occurred in 8 per 1000 (38/4884) live births, with Plasmodium falciparum accounting for 76.3% (29) and P. vivax for 15.8% (6) of infections. Maternal malaria at delivery (adjusted odds ratio [AOR], 9.5; 95% confidence interval [CI], 4.2–21.5; P < .001), age ≤ 16 years (AOR, 4; 95% CI, 1.4–12.1; P = .011), and prior malaria during pregnancy (AOR, 2.2; 95% CI, 1.1–4.4, P = .022) were independent risk factors for vertical transmission. Of 29 mothers and neonates with contemporaneous peripheral parasitemia, 17% (5) had discordant parasite species, suggesting possible antenatal malaria transmission. Newborns with malaria were at significantly greater risk of low birth weight (AOR, 2.8; 95% CI, 1.2–6.6; P = .002). Following introduction of dihydroartemisinin-piperaquine for uncomplicated malaria in the second and third trimesters of pregnancy, congenital malaria incidence fell from 3.2% to 0.2% (odds ratio, 0.07; 95% CI, .03–.15; P < .001).

Conclusions. Congenital malaria is an important cause of neonatal morbidity in this region co-endemic for P. falciparum and P. vivax malaria. The introduction of artemisinin-combination therapy was associated with a significant risk reduction in the vertical transmission of malaria.

Amplification of pvmdr1 associated with multidrug-resistant Plasmodium vivax

BACKGROUND

Multidrug-resistant strains of Plasmodium vivax are emerging in Southeast Asia.

METHODS

In vitro drug susceptibility and pvmdr1 genotype were determined in P. vivax field isolates from Indonesia and Thailand.

RESULTS

Increased pvmdr1 copy number was present in 21% of isolates from Thailand (15/71) and none from Indonesia (0/114; P < .001). Compared with Indonesian isolates, the median IC(50) of Thai isolates was lower for chloroquine (36 vs. 114 nmol/L; P < .001) but higher for amodiaquine (34 vs. 13.7 nmol/L; P = .032), artesunate (8.33 vs. 1.58 nmol/L; P < .001), and mefloquine (111 vs. 9.87 nmol/L; P < .001). In 11 cryopreserved Thai isolates, those with increased pvmdr1 copy number had a higher IC(50) for mefloquine (78.6 vs. 38 nmol/L for single-copy isolates; P = .006). Compared with isolates with the wild-type allele, the Y976F mutation of pvmdr1 was associated with reduced susceptibility to chloroquine (154 nmol/L [range, 4.6-3505] vs. 34 nmol/L [range, 6.7-149]; P < .001) but greater susceptibility to artesunate (1.8 vs. 9.5 nmol/L; P = .009) and mefloquine (14 vs. 121 nmol/L; P < .001).

CONCLUSIONS

Amplification of pvmdr1 and single-nucleotide polymorphisms are correlated with susceptibility of P. vivax to multiple antimalarial drugs. Chloroquine and mefloquine appear to exert competitive evolutionary pressure on pvmdr1, similar to that observed with pfmdr1 in Plasmodium falciparum.

Clinical and pharmacological determinants of the therapeutic response to dihydroartemisinin-piperaquine for drug-resistant malaria

Dihydroartemisinin-piperaquine (DHP) is an important new treatment for drug-resistant malaria, although pharmacokinetic studies on the combination are limited. In Papua, Indonesia, we assessed determinants of the therapeutic efficacy of DHP for uncomplicated malaria. Plasma piperaquine concentrations were measured on day 7 and day 28, and the cumulative risk of parasitological failure at day 42 was calculated using survival analysis. Of the 598 patients in the evaluable population 342 had infections with Plasmodium falciparum, 83 with Plasmodium vivax, and 173 with a mixture of both species. The unadjusted cumulative risks of recurrence were 7.0% (95% confidence interval [CI]: 4.6 to 9.4%) for P. falciparum and 8.9% (95% CI: 6.0 to 12%) for P. vivax. After correcting for reinfections the risk of recrudescence with P. falciparum was 1.1% (95% CI: 0.1 to 2.1%). The major determinant of parasitological failure was the plasma piperaquine concentration. A concentration below 30 ng/ml on day 7 was observed in 38% (21/56) of children less than 15 years old and 22% (31/140) of adults (P = 0.04), even though the overall dose (mg per kg of body weight) in children was 9% higher than that in adults (P < 0.001). Patients with piperaquine levels below 30 ng/ml were more likely to have a recurrence with P. falciparum (hazard ratio [HR] = 6.6 [95% CI: 1.9 to 23]; P = 0.003) or P. vivax (HR = 9.0 [95% CI: 2.3 to 35]; P = 0.001). The plasma concentration of piperaquine on day 7 was the major determinant of the therapeutic response to DHP. Lower plasma piperaquine concentrations and higher failure rates in children suggest that dose revision may be warranted in this age group.

Dihydroartemisinin-piperaquine versus artesunate-amodiaquine: superior efficacy and posttreatment prophylaxis against multidrug-resistant Plasmodium falciparum and Plasmodium vivax malaria

BACKGROUND

Antimalarial drug resistance is now well established in both Plasmodium falciparum and Plasmodium vivax. In southern Papua, Indonesia, where both strains of plasmodia coexist, we have been conducting a series of studies to optimize treatment strategies.

METHODS

We conducted a randomized trial that compared the efficacy and safety of dihydroartemisinin-piperaquine (DHP) with artesunate-amodiaquine (AAQ). The primary end point was the overall cumulative parasitological failure rate at day 42.

RESULTS

Of the 334 patients in the evaluable patient population, 185 were infected with P. falciparum, 80 were infected with P. vivax, and 69 were infected with both species. The overall parasitological failure rate at day 42 was 45% (95% confidence interval [CI], 36%-53%) for AAQ and 13% (95% CI, 7.2%-19%) for DHP (hazard ratio [HR], 4.3; 95% CI, 2.5-7.2; P<.001). Rates of both recrudescence of P. falciparum infection and recurrence of P. vivax infection were significantly higher after receipt of AAQ than after receipt of DHP (HR, 3.4 [95% CI, 1.2-9.4] and 4.3 [95% CI, 2.2-8.2], respectively; P<.001). By the end of the study, AAQ recipients were 2.95-fold (95% CI, 1.2- to 4.9-fold) more likely to be anemic and 14.5-fold (95% CI, 3.4- to 61-fold) more likely to have carried P. vivax gametocytes.

CONCLUSIONS

DHP was more effective and better tolerated than AAQ against multidrug-resistant P. falciparum and P. vivax infections. The prolonged therapeutic effect of piperaquine delayed the time to P. falciparum reinfection, decreased the rate of recurrence of P. vivax infection, and reduced the risk of P. vivax gametocyte carriage and anemia.

Two fixed-dose artemisinin combinations for drug-resistant falciparum and vivax malaria in Papua, Indonesia: an open-label randomised comparison

BACKGROUND

The burden of Plasmodium vivax infections has been underappreciated, especially in southeast Asia where chloroquine resistant strains have emerged. Our aim was to compare the safety and efficacy of dihydroartemisinin-piperaquine with that of artemether-lumefantrine in patients with uncomplicated malaria caused by multidrug-resistant P falciparum and P vivax.

METHODS

774 patients in southern Papua, Indonesia, with slide-confirmed malaria were randomly assigned to receive either artemether-lumefantrine or dihydroartemisinin-piperaquine and followed up for at least 42 days. The primary endpoint was the overall cumulative risk of parasitological failure at day 42 with a modified intention-to-treat analysis. This trial is registered with ClinicalTrials.gov, trial number 00157833.

FINDINGS

Of the 754 evaluable patients enrolled, 466 had infections with P falciparum, 175 with P vivax, and 113 with a mixture of both species. The overall risk of failure at day 42 was 43% (95% CI 38-48) for artemether-lumefantrine and 19% (14-23) for dihydroartemisinin-piperaquine (hazard ratio=3.0, 95% CI 2.2-4.1, p<0.0001). After correcting for reinfections, the risk of recrudescence of P falciparum was 4.4% (2.6-6.2) with no difference between regimens. Recurrence of vivax occurred in 38% (33-44) of patients given artemether-lumefantrine compared with 10% (6.9-14.0) given dihydroartemisinin-piperaquine (p<0.0001). At the end of the study, patients receiving dihydroartemisinin-piperaquine were 2.0 times (1.2-3.6) less likely to be anaemic and 6.6 times (2.8-16) less likely to carry vivax gametocytes than were those given artemether-lumefantrine.

INTERPRETATION

Both dihydroartemisinin-piperaquine and artemether-lumefantrine were safe and effective for the treatment of multidrug-resistant uncomplicated malaria. However, dihydroartemisinin-piperaquine provided greater post-treatment prophylaxis than did artemether-lumefantrine, reducing P falciparum reinfections and P vivax recurrences, the clinical public-health importance of which should not be ignored.

Factors contributing to anemia after uncomplicated falciparum malaria

The factors contributing to anemia in falciparum malaria were characterized in 4,007 prospectively studied patients on the western border of Thailand. Of these, 727 patients (18%) presented with anemia (haematocrit < 30%), and 1% (55 of 5,253) required blood transfusion. The following were found to be independent risk factors for anemia at admission: age < 5 years, a palpable spleen, a palpable liver, recrudescent infections, being female, a prolonged history of illness (> 2 days) before admission, and pure Plasmodium falciparum infections rather than mixed P. falciparum and Plasmodium vivax infections. The mean maximum fractional fall in hematocrit after antimalarial treatment was 14.1% of the baseline value (95% confidence interval [CI], 13.6-14.6). This reduction was significantly greater in young children (aged < 5 years) and in patients with a prolonged illness, high parasitemia, or delayed parasite clearance. Loss of parasitized erythrocytes accounted for < 10% of overall red blood cell loss. Hematological recovery was usually complete within 6 weeks, but it was slower in patients who were anemic at admission (adjusted hazards ratio [AHR], 1.9, 95% CI, 1.5-2.3), and those whose infections recrudesced (AHR, 1.2, 95% CI, 1.01-1.5). Half the patients with treatment failure were anemic at 6 weeks compared with 19% of successfully treated patients (relative risk, 2.8, 95% CI, 2.0-3.8). Patients coinfected with P. vivax (16% of the total) were 1.8 (95% CI, 1.2-2.6) times less likely to become anemic and recovered 1.3 (95% CI, 1.0-1.5) times faster than those with P. falciparum only. Anemia is related to drug resistance and treatment failure in uncomplicated malaria. Children aged < 5 years of age were more likely than older children or adults to become anemic. Coinfection with P. vivax attenuates the anemia of falciparum malaria, presumably by modifying the severity of the infection.

Drug resistant falciparum malaria: clinical consequences and strategies for prevention

The rising prevalence of multidrug resistant falciparum malaria is occurring at an alarming rate and has serious implications for the health of many of the world's poorest countries. The dangers of not changing treatment practices immediately are huge and irreversible, threatening to both exacerbate the scale and scope of the malaria pandemic, and deprive policymakers of future options against the disease. If a health care disaster is to be avoided then massive and long term funding is urgently required. Funds need to be applied in a cohesive manner, accountable to funding bodies and tailored to the specifics of each endemic region. The key elements of such an approach should be improving early diagnosis and treatment of infection and the deployment of combination regimens containing an artemisinin derivative. These short term measures will need to be accompanied by a longer term strategy to encourage antimalarial drug research and development.

Mefloquine pharmacokinetic-pharmacodynamic models: implications for dosing and resistance

Antimalarial resistance develops and spreads when spontaneously occurring mutant malaria parasites are selected by concentrations of antimalarial drug which are sufficient to eradicate the more sensitive parasites but not those with the resistance mutation(s). Mefloquine, a slowly eliminated quinoline-methanol compound, is the most widely used drug for the treatment of multidrug-resistant falciparum malaria. It has been used at doses ranging between 15 and 25 mg of base/kg of body weight. Resistance to mefloquine has developed rapidly on the borders of Thailand, where the drug has been deployed since 1984. Mathematical modeling with population pharmacokinetic and in vivo and in vitro pharmacodynamic data from this region confirms that, early in the evolution of resistance, conventional assessments of the therapeutic response </=28 days after treatment underestimate considerably the level of resistance. Longer follow-up is required. The model indicates that initial deployment of a lower (15-mg/kg) dose of mefloquine provides a greater opportunity for the selection of resistant mutants and would be expected to lead more rapidly to resistance than de novo use of the higher (25-mg/kg) dose.

Artemisinin drugs: novel antimalarial agents

Artemisinin and its derivatives, artesunate and artemether, represent a new class of antimicrobial drug with potent activity against Plasmodium falciparum. Although they show excellent efficacy in both severe and uncomplicated malaria, dosage regimens still need to be optimised and pharmacokinetic profiles defined. In the treatment of uncomplicated malaria, the artemisinin drugs should be used in combination with a long acting antimalarial to protect both drugs against the emergence of resistance. In the treatment of severe malaria, parenteral artemether is at least as effective as quinine and is simpler to use. The use of rectal preparations of artesunate and artemisinin at the rural health level will facilitate early initiation of the treatment of falciparum malaria and this may reduce the proportion of patients progressing to severe disease. All of the artemisinin drugs have comparable efficacy; the choice of derivative should be based upon availability, cost and quality of the preparation. Artemisinin, artesunate and artemether are well-tolerated in both adults and children, with no evidence to date of serious clinical toxicity.

Plasmodium falciparum antimalarial drug susceptibility on the north-western border of Thailand during five years of extensive use of artesunate-mefloquine

Following a marked decline in the efficacy in vivo of mefloquine between 1990 and 1994, a combination of artesunate (4 mg/kg/d for 3 d) and mefloquine (25 mg/kg) has been used as first line treatment of uncomplicated falciparum malaria in camps for displaced persons located along the north-western border of Thailand. Antimalarial drug susceptibility of fresh isolates of Plasmodium falciparum from this population was evaluated using a radioisotope microdilution assay between 1995 and 1999. In total, 268 isolates were collected, of which 189 were from primary infections and 79 from recrudescent infections. The geometric mean 50% inhibitory concentration (IC50) values from primary infections were: dihydroartemisinin 1.2 ng/mL, artesunate 1.6 ng/mL, artemether 4.8 ng/mL, atovaquone 0.4 ng/mL, lumefantrine 32 ng/mL, chloroquine 149 ng/mL, quinine 354 ng/mL, mefloquine 27 ng/mL and halofantrine 4.1 ng/mL. A significant positive correlation was found between the susceptibility in vitro to artesunate and quinine (r = 0.43, P < 0.001), mefloquine (r = 0.46, P < 0.001), and halofantrine (r = 0.51, P < 0.001). These levels of resistance in vitro are among the highest reported and confirm continuing high level multidrug resistance in this area. Despite intensive use of the combination between 1995 and 1999 there has been a significant improvement in mefloquine sensitivity (P < 0.001) and artesunate sensitivity (P < 0.001). This supports observations in vivo that the combination of artesunate and mefloquine has reversed the previous decline in mefloquine sensitivity.

A case-control auditory evaluation of patients treated with artemisinin derivatives for multidrug-resistant Plasmodium falciparum malaria

The artemisinin derivatives are now used widely in areas with multidrug-resistant Plasmodium falciparum malaria such as Southeast Asia, but concerns remain over their potential for neurotoxicity. Mice, rats, dogs, and monkeys treated with high doses of intramuscular artemether or arteether develop an unusual pattern of focal damage to brain stem nuclei (particularly those involved in auditory processing). To investigate whether a similar toxic effect occurs in patients treated with these compounds, clinical neurologic evaluation, audiometry and early latency auditory evoked responses were measured in a single-blind comparison of 79 patients who had been treated with > or =2 courses of oral artemether or artesunate within the previous 3 years, and 79 age- and sex-matched controls living in a malaria-endemic area on the northwestern border of Thailand. There were no consistent differences in any of these test results between the cases and controls. This study failed to detect any evidence of significant neurotoxicity in patients treated previously with oral artemether or artesunate for acute malaria.

The pfmdr1 gene is associated with a multidrug-resistant phenotype in Plasmodium falciparum from the western border of Thailand

On the western border of Thailand, Plasmodium falciparum has become resistant to almost all antimalarial agents. The molecular basis of resistance in these parasite populations has not been well characterized. This study assessed genetic polymorphisms in the pfmdr1 gene in 54 parasites collected from the western border of Thailand to determine the relationship of pfmdr1 copy number and codon mutations with parasite sensitivities to mefloquine, chloroquine, halofantrine, quinine, and artesunate assessed in vitro. A point mutation at codon 86 (resulting in a change of Asn to Tyr) was associated with a significantly lower 50% inhibitory concentration (IC(50)) of mefloquine (median, 9 ng/ml versus 52.4 ng/ml; P = 0.003). Overall 35% of the isolates (19 of 54) had an increase in pfmdr1 copy number, and all 19 carried the wild-type allele at codon 86. Increased pfmdr1 copy number was associated with higher IC(50)s of mefloquine (P = 0.04) and artesunate (P = 0.005), independent of polymorphism at codon 86. The relationship between pfmdr1 and resistance to structurally distinct antimalarial agents confirms the presence of a true multidrug-resistant phenotype.

Genetic analysis of Plasmodium falciparum infections on the north-western border of Thailand

Genetic characterization of Plasmodium falciparum infections in north-western Thailand, a region of low transmission intensity (1 infection/person each year), has found a comparable number of parasite genotypes per infected person to regions with hyperendemic malaria. Clone multiplicity and parasite diversity were found to be homogeneous across 129 infected individuals comprising a range of age-groups (1.32 parasite genotypes; n = 98), patients (aged 2-16 years) with recrudescent infections (1.54; n = 13), and pregnant women (1.61; n = 18). Individuals belonging to groups with a high risk of infection, as deduced by clinical epidemiology, did not harbour a higher number of clones per infection, nor greater parasite diversity than low-risk groups. In fact, multiple genotype infections were as common in low-risk groups, suggesting that there is frequent transmission of polyclonal infections from a single inoculum, rather than superinfection. Such a polyclonal transmission system would enable generation of extensive parasite diversity by recombination, despite the low level of transmission. However, co-infection with P. vivax was associated with fewer P. falciparum genotypes per infection.

Artesunate/mefloquine treatment of multi-drug resistant falciparum malaria

On the western border of Thailand, in an area endemic for multi-drug resistant Plasmodium falciparum malaria, therapeutic responses were assessed in 1967 patients with uncomplicated falciparum malaria treated with 3 d of artesunate (total dose 12 mg/kg) plus mefloquine (total dose 25 mg/kg). The regimen was well tolerated and resulted in a rapid clinical response; within 48 h, 96% of patients were aparasitaemic and 94% were afebrile. After correcting for reinfections, the cure rate by day 42 was 89% (95% confidence interval [95% CI] 87-91%). Three independent factors were found to predict recrudescence: age < 14 years (adjusted hazards ratio [AHR] = 1.6, 95% CI 1.1-2.3), initial parasitaemia greater than > 40,000/microL (AHR = 1.6, 95%, CI 1.2-2.2), and pure P. falciparum infections (AHR = 1.8, 95% CI 1.3-2.7). These 3 factors combined accounted for 62% of all treatment failures. Patients who received mefloquine on admission with a high admission parasitaemia (> 40,000/microL) had a three-fold (95% CI 1.3-7) risk of subsequent recrudescence compared with those who received their mefloquine on the second or third day (P = 0.01). There has been no decline in the efficacy of the 3 d artesunate plus mefloquine regimen since it was introduced in 1992. This regimen is safe, well tolerated, and highly effective in the treatment of multi-drug resistant falciparum malaria.

Mefloquine in infants and young children

In an area where multi-drug resistance in Plasmodium falciparum is a particular problem, more than 500 children under 5 years of age weighing > 5 kg were treated with mefloquine, either alone or combined with an artemisinin derivative, and followed up for a minimum of 28 days. The principal adverse effect was vomiting and this was associated with reduced efficacy of treatment (even when treatment was repeated). Later adverse effects occurred less frequently than in adults. There was no serious toxicity and, in particular, there were no neuropsychiatric side-effects. The high dose of mefloquine (25 mg/kg) required in this area is well tolerated by young children. It should be given in a divided dose of 15 mg/kg initially, followed by 10 mg/kg > or = 12 hours later.

Effects of artemisinin derivatives on malaria transmissibility

BACKGROUND

On the western border of Thailand the efficacy of mefloquine in the treatment of falciparum malaria has declined while gametocyte carriage rates have increased, which suggests increased transmissibility of these resistant infections. We compared the following antimalarial drugs in relation to subsequent Plasmodium falciparum gametocyte carriage: mefloquine, halofantrine, quinine, and the artemisinin derivatives.

METHODS

Between 1990 and 1995 we assessed gametocytaemia in a series of prospective studies of antimalarial drug treatment in 5193 adults and children with acute uncomplicated falciparum malaria in an area of malarious hill forest on the western border of Thailand. Weekly parasite counts from thick and thin blood films were done during the 4-week (1990-93) or 9-week (1993-95) follow-up period. Gametocyte positivity rates and person gametocyte week (PGW) rates were calculated to measure gametocyte carriage and transmission potential.

FINDINGS

In primary P falciparum infections the gametocyte carriage rate was significantly higher after treatment with mefloquine than after treatment with the artemisinin derivatives (PGW 34.1 [95% CI 25.2-42.9] vs 3.9 [1.9-5.9] per 1000 person weeks; relative risk 8.0 [4.1-15.6]; p<0.0001). Recrudescent infections were associated with increased gametocyte carrier rates (relative risk 2.2 [1.6-3.0]; p<0.0001), but retreatment with artemisinin derivatives reduced subsequent gametocyte carriage 18.5 fold [3.5-98] compared with mefloquine retreatment and 6.8 fold (3.1-15.1) compared with quinine retreatment (p<0.001). The introduction of the artemisinin derivatives in routine treatment at this study site in mid 1994 was associated with a reduction in the subsequent incidence of falciparum malaria of 47 (25-69)%

INTERPRETATION

Although environmental changes affect vector numbers, and hence malaria incidence, artemisinin derivatives were found to reduce the transmission potential of falciparum malaria. Widespread introduction of artemisinin derivatives in the treatment of falciparum malaria may prevent the spread of multidrug resistance.

Artesunate versus artemether in combination with mefloquine for the treatment of multidrug-resistant falciparum malaria

To compare the therapeutic efficacy of oral artesunate and artemether in combination with mefloquine for the treatment of multidrug resistant malaria, a trial was conducted in 540 adults and children on the Thai-Myanmar border. Three regimens were compared: artesunate (4 mg/kg/d for 3 d), artemether (4 mg/kg/d for 3 d), both in combination with mefloquine (25 mg/kg), and a single dose of mefloquine (25 mg/kg). The artesunate and artemether regimens gave very similar clinical and parasitological responses, and were both very well tolerated. There was no significant adverse effect attributable to the artemisinin derivatives. Fever and parasite clearance times with mefloquine alone were significantly longer (P < 0.001). After adjusting for reinfections the failure rates were 13.9% for the artesunate combination, 12.3% for the artemether combination and 49.2% for mefloquine alone (P < 0.0001; relative risk 3.8 [95% confidence interval 2.6-5.4]). Mefloquine should no longer be used alone for the treatment of multidrug resistant falciparum malaria in this area. Three-day combination regimens with artesunate or artemether are well tolerated and more effective.

New antimalarials. A risk-benefit analysis

Although more than 40% of the world's population live in malaria endemic areas, there are only 6 available antimalarial drugs for the treatment of Plasmodium falciparum infections. Three of these have been developed in the last 20 years and are discussed in this review. Mefloquine is relatively well tolerated and has the advantage of a single day regimen. It has ideal properties for prophylactic use. However, although rare, serious adverse reactions do occur and the drug cannot be used in severe malaria. Resistance has already emerged in some parts of the world. Halofantrine is also well tolerated and has a rapid antimalarial activity. It is more expensive than other antimalarials and the existence of cross-resistance links its usefulness to the demise of mefloquine. The discovery of a potentially lethal cardiotoxicity associated with halofantrine casts a further shadow over its use. The artemisinin derivatives represent an exciting breakthrough in the treatment of malaria. They are cheap and have a very rapid action. They seem remarkably free from toxic adverse effects, although the neurotoxicity seen in animal studies with the liposoluble derivatives gives rise for concern. However, the lack of pharmacokinetic and toxicity data as yet preclude their approval by Western drug regulation authorities. All antimalarials are threatened by the emergence of parasite resistance. Combination therapy using mefloquine and an artemisinin derivative may provide a way in which resistance can be combated.

A protocol system to satisfy research specific, disease specific, physician specific, and patient specific informational needs

The Department of Medicine at Loyola University Medical Center Chicago (LUMC) has developed and is utilizing a Patient Information Protocol System (PIPS) to address clinical and research informational needs. PIPS, an integrated module of the department's Patient Information Management System (PIMS), enables end-users to access pre-defined informational templates or "protocols". Protocols detail pre-defined data requirements for patient management or clinical research needs. Each protocol consists of a defined collection of protocol elements. Protocol elements belong to an object group which has several defined attributes (e.g. description, acceptable ranges or inputs, units, and grouping keywords). Approximately 3,500 protocol elements have been identified to define treatments/drugs, symptoms/toxicity, clinical labs, x-rays/scans, physical findings, and lesion groups. Utilizing protocols, PIPS permits end-users to selectively review or capture clinical information. Patients may have several active protocols. PIPS interacts with a specialized database gateway to permit automatic capture of clinical laboratories information, and with reporting systems to produce one of several "chart-ready", time-oriented protocol summary reports. Data extraction programs operate in conjunction with PIPS to facilitate exporting of data for statistical analysis. PIPS has been in operation for over 24 months and has 63 defined protocols (40 clinical research and 23 patient care).

Comparison of Methods for Determination of Sulfur in Fertilizer: Collaborative Study

Methods with applications for total sulfur (sulfate, elemental sulfur) in dry fertilizers, for total sulfur (sulfate, sulfite, thiosulfate, sulfide) in liquid fertilizers, for total sulfur (elemental sulfur) in sulfur-coated urea and elemental sulfur formulations, and for thiosulfate sulfur in ammonium thiosulfate liquid fertilizer (12-0-0, 26 S), and 7 samples with background and directions were submitted to 12 collaborating laboratories for comparison to official methods 2.160–2.161 and 2.162. The methods studied are simple and rapid, and recover the total sulfur in fertilizers containing high levels of elemental sulfur and thiosulfate sulfur. Method 2.160–2.161 does not recover total sulfur in these products. The first 3 methods have been adopted as official first action, and the present official methods for sulfur, 2.160–2.161 and 2.162, have been repealed, official first action.

In vitro neutralizing capacity of commercially available antacid mixtures, and their role in the treatment of peptic ulcer

An in vitro technique has been used to determine the neutralizing capacity of liquid antacids. Many locally available preparations have been tested, and the results indicate that they vary strikingly in both neutralizing capacity and cost. This study re-emphasizes the place of antacids in peptic ulcer therapy.