Optimal Antimalarial Dose Regimens for Sulfadoxine-Pyrimethamine with or without Azithromycin in Pregnancy Based on Population Pharmacokinetic Modeling.

Optimal dosing of sulfadoxine-pyrimethamine (SP) as intermittent preventive treatment in pregnancy remains to be established, particularly when coadministered with azithromycin (AZI). To further characterize SP pharmacokinetics in pregnancy, plasma concentration-time data from 45 nonpregnant and 45 pregnant women treated with SP-AZI (n = 15 in each group) and SP-chloroquine (n = 30 in each group) were analyzed. Population nonlinear mixed-effect pharmacokinetic models were developed for pyrimethamine (PYR), sulfadoxine (SDOX), and N-acetylsulfadoxine (the SDOX metabolite NASDOX), and potential covariates were included. Pregnancy increased the relative clearance (CL/F) of PYR, SDOX, and NASDOX by 48, 29, and 70%, respectively, as well as the relative volumes of distribution (V/F) of PYR (46 and 99%) and NASDOX (46%). Coadministration of AZI resulted in a greater increase in PYR CL/F (80%) and also increased NASDOX V/F by 76%. Apparent differences between these results and those of published studies of SP disposition may reflect key differences in study design, including the use of an early postpartum follow-up study rather than a nonpregnant comparator group. Simulations based on the final population model demonstrated that, compared to conventional single-dose SP in nonpregnant women, two such doses given 24 h apart should ensure that pregnant women have similar drug exposure, while three daily SP doses may be required if SP is given with AZI. The results of past and ongoing trials using recommended adult SP doses with or without AZI in pregnant women may need to be interpreted in light of these findings and consideration given to using increased doses in future trials.

How important is gametocyte clearance after malaria therapy?

There has been increasing interest in the role of malaria drugs in preventing malaria transmission from humans to mosquitoes, which would help augment malaria control and elimination strategies. Nevertheless, only one stage in the malaria parasite life cycle, the gametocyte, is infectious to mosquitoes. The Worldwide Antimalarial Resistance Network (WWARN) have analyzed data from 48,840 patients from 141 clinical trials in order to define the nature and determinants of gametocyte clearance following artemisinin combination treatment (ACT) for symptomatic malaria infections. However, the presence of gametocytes does not always predict their infectivity, meaning that the microscopy-based methods used by the WWARN investigators represent an imperfect surrogate marker of transmissibility. Their findings, that some ACTs clear gametocytes faster than others, should be interpreted in light of these limitations and important gaps in our understanding of the biology and epidemiology of malaria transmission.Please see related article: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-016-0621-7.

Parasite clearance after malaria therapy: staying a step ahead of drug resistance.

The discovery and development of the artemisinin class of antimalarial drugs is one of the great recent success stories of global health. However, after at least two decades of successful use, resistance has finally emerged and appears to be spreading rapidly throughout South-East Asia in spite of our best efforts at containment. If this were also to occur in Africa, it would have disastrous implications for the continent subject to the world's greatest burden of Plasmodium falciparum. The earliest indications of incipient artemisinin resistance may be a slowing of the rate at which parasites are cleared from the blood following treatment. The Worldwide Antimalarial Resistance Network have analysed data from 29,493 patients from 84 clinical trials in order to define the nature and determinants of early parasite clearance following artemisinin-based treatment in African populations. In doing so, they lay the foundation for systems intended to enable the earliest possible detection of emerging artemisinin resistance in Africa. Please see related article: http://www.biomedcentral.com/1741-7015/13/212.

Characterization of treatment failure in efficacy trials of drugs against Plasmodium vivax by genotyping neutral and drug resistance-associated markers.

Plasmodium vivax intervention trials customarily report uncorrected treatment failure rates. Application of recrudescence-reinfection genotyping and drug resistance single-nucleotide polymorphism typing to a 4-arm comparative efficacy trial illustrated that molecular approaches can assist in understanding the relative contributions of true drug resistance (recurrent with same genotype) and new infections to treatment failure. The PCR-corrected adequate clinical and parasitologic response may constitute an informative secondary endpoint in future P. vivax drug trials.

Meningeal inflammation increases artemether concentrations in cerebrospinal fluid in Papua New Guinean children treated with intramuscular artemether.

Although the artemisinin-associated neurotoxicity identified in vitro and in animal studies has not been confirmed clinically, only one adult study has measured cerebrospinal fluid (CSF) concentrations after administration of conventional doses. Potential artemisinin neurotoxicity could be serious in children, especially those with meningitis and, consequently, a compromised blood-brain barrier. We measured CSF/plasma artemether and dihydroartemisinin (DHA) concentrations in 32 Papua New Guinean children with a mean age of 39 months with suspected or proven severe falciparum malaria who underwent a single lumbar puncture after intramuscular artemether administration. CSF artemether concentrations were 0 to 43.5 µg/liter and CSF concentration/plasma concentration ratios were 0 to 38.1%. DHA was measurable in CSF in only two children. The seven children with meningeal inflammation (CSF white cell count > 20/mm(3)) had higher CSF artemether concentration/plasma artemether concentration ratios than those without (median, 6.7% [interquartile ratio, 2.5 to 27.8%]% versus 0.0% [interquartile ratio, 0.0 to 2.5%]; P = 0.002). Meningeal inflammation was associated with a 4.6-fold increase in the CSF artemether concentration/plasma artemether concentration ratio in a population pharmacokinetic model. These data suggest that pharmacovigilance should be heightened when intramuscular artemether is given to severely ill children with evidence of meningeal inflammation.

A trial of combination antimalarial therapies in children from Papua New Guinea.

BACKGROUND: Malaria control is difficult where there is intense year-round transmission of multiple plasmodium species, such as in Papua New Guinea. METHODS: Between April 2005 and July 2007, we conducted an open-label, randomized, parallel-group study of conventional chloroquine-sulfadoxine-pyrimethamine and artesunate-sulfadoxine-pyrimethamine, dihydroartemisinin-piperaquine, and artemether-lumefantrine in children in Papua New Guinea 0.5 to 5 years of age who had falciparum or vivax malaria. The primary end point was the rate of adequate clinical and parasitologic response at day 42 after the start of treatment with regard to Plasmodium falciparum, after correction for reinfections identified through polymerase-chain-reaction (PCR) genotyping of polymorphic loci in parasite DNA. Secondary end points included the rate of adequate clinical and parasitologic response at day 42 with regard to P. vivax without correction through PCR genotyping. RESULTS: Of 2802 febrile children screened, 482 with falciparum malaria and 195 with vivax malaria were included. The highest rate of adequate clinical and parasitologic response for P. falciparum was in the artemether-lumefantrine group (95.2%), as compared with 81.5% in the chloroquine-sulfadoxine-pyrimethamine group (P=0.003), 85.4% in the artesunate-sulfadoxine-pyrimethamine group (P=0.02), and 88.0% in the dihydroartemisinin-piperaquine group (P=0.06). The rate of adequate clinical and parasitologic response for P. vivax in the dihydroartemisinin-piperaquine group (69.4%) was more than twice that in each of the other three treatment groups. The in vitro chloroquine and piperaquine levels that inhibited growth of local P. falciparum isolates by 50% correlated significantly (P<0.001). Rash occurred more often with artesunate-sulfadoxine-pyrimethamine and dihydroartemisinin-piperaquine than with chloroquine-sulfadoxine-pyrimethamine (P=0.004 for both comparisons). CONCLUSIONS: The most effective regimens were artemether-lumefantrine against P. falciparum and dihydroartemisinin-piperaquine against P. vivax. The relatively high rate of treatment failure with dihydroartemisinin-piperaquine against P. falciparum may reflect cross-resistance between chloroquine and piperaquine. (Australian New Zealand Clinical Trials Registry number, ACTRN12605000550606.)

Cost-effectiveness of artemisinin combination therapy for uncomplicated malaria in children: data from Papua New Guinea.

OBJECTIVE: To compare the cost-effectiveness of conventional antimalarial therapy with that of three artemisinin combination treatment regimens in children from Papua New Guinea aged 6 to 60 months. METHODS: An incremental cost-effectiveness analysis was performed using data from 656 children with Plasmodium falciparum and/or P. vivax malaria who participated in a large intervention trial in two clinics in northern Papua New Guinea. The children were randomized to one of the following groups: (i) conventional treatment with chloroquine plus sulfadoxine plus pyrimethamine (CQ+S+P); (ii) artesunate plus S plus P; (iii) dihydroartemisinin plus piperaquine (DHA+PQ); and (iv) artemether plus lumefantrine (A+L). For treatment outcomes, World Health Organization definitions were used. The cost of transport between home and the clinic plus direct health-care costs served as a basis for determining each regimen's incremental cost per incremental treatment success relative to CQ+S+P by day 42 and its cost per life year saved. FINDINGS: A+L proved to be the most effective regimen against P. falciparum malaria and was highly cost-effective at 6.97 United States dollars (US$) per treatment success (about US$ 58 per life year saved). DHA+PQ was the most effective regimen against P. vivax malaria and was more cost-effective than CQ+S+P. CONCLUSION: A+L and DHA+PQ are highly cost-effective regimens for the treatment of paediatric P. falciparum and P. vivax malaria, respectively, in parts of Papua New Guinea. Future research will be required to determine if these findings hold true for other territories in Asia and Oceania with similar malaria epidemiology.

Pharmacokinetics of chloroquine and monodesethylchloroquine in pregnancy.

In order to determine the pharmacokinetic disposition of chloroquine (CQ) and its active metabolite, desethylchloroquine (DECQ), when administered as intermittent presumptive treatment in pregnancy (IPTp) for malaria, 30 Papua New Guinean women in the second or third trimester of pregnancy and 30 age-matched nonpregnant women were administered three daily doses of 450 mg CQ (8.5 mg/kg of body weight/day) in addition to a single dose of sulfadoxine-pyrimethamine. For all women, blood was taken at baseline; at 1, 2, 4, 6, 12, 18, 24, 30, 48, and 72 h posttreatment; and at 7, 10, 14, 28, and 42 days posttreatment. Plasma was subsequently assayed for CQ and DECQ by high-performance liquid chromatography, and population pharmacokinetic modeling was performed. Pregnant subjects had significantly lower area under the plasma concentration-time curve for both CQ (35,750 versus 47,892 microg.h/liter, P < 0.001) and DECQ (23,073 versus 41,584 microg.h/liter, P < 0.001), reflecting significant differences in elimination half-lives and in volumes of distribution and clearances relative to bioavailability. Reduced plasma concentrations of both CQ and DECQ could compromise both curative efficacy and posttreatment prophylactic properties in pregnant patients. Higher IPTp CQ doses may be desirable but could increase the risk of adverse hemodynamic effects.

Pharmacokinetic properties of azithromycin in pregnancy.

Azithromycin (AZI) is an azalide antibiotic with antimalarial activity that is considered safe in pregnancy. To assess its pharmacokinetic properties when administered as intermittent preventive treatment in pregnancy (IPTp), two 2-g doses were given 24 h apart to 31 pregnant and 29 age-matched nonpregnant Papua New Guinean women. All subjects also received single-dose sulfadoxine-pyrimethamine (SP) (1,500 mg or 75 mg) or chloroquine (450-mg base daily for 3 days). Blood samples were taken at 0, 1, 2, 3, 6, 12, 24, 32, 40, 48, and 72 h and on days 4, 5, 7, 10, and 14 for AZI assay by ultra-high-performance liquid chromatography-tandem mass spectrometry. The treatments were well tolerated. Using population pharmacokinetic modeling, a three-compartment model with zero-order followed by first-order absorption and no lag time provided the best fit. The areas under the plasma concentration-time curve (AUC(0-infinity)) (28.7 and 31.8 mg.h liter(-1) for pregnant and nonpregnant subjects, respectively) were consistent with the results of previous studies, but the estimated terminal elimination half-lives (78 and 77 h, respectively) were generally longer. The only significant relationship for a range of potential covariates, including malarial parasitemia, was with pregnancy, which accounted for an 86% increase in the volume of distribution of the central compartment relative to bioavailability without a significant change in the AUC(0-infinity). These data suggest that AZI can be combined with compounds with longer half-lives, such as SP, in combination IPTp without the need for dose adjustment.

In vitro sensitivity of Plasmodium falciparum to conventional and novel antimalarial drugs in Papua New Guinea.

OBJECTIVE: Recent clinical studies have shown high rates of malaria treatment failure in endemic areas of Papua New Guinea (PNG), necessitating a change of treatment from chloroquine (CQ) or amodiaquine (AQ) plus sulphadoxine-pyrimethamine to the artemisinin combination therapy (ACT) artemether plus lumefantrine (LM). To facilitate the monitoring of antimalarial drug resistance in this setting, we assessed the in vitro sensitivity of Plasmodium falciparum isolates from Madang Province. METHODS: A validated colorimetric lactate dehydrogenase assay was used to assess growth inhibition of 64 P. falciparum isolates in the presence of nine conventional or novel antimalarial drugs [CQ, AQ, monodesethyl-amodiaquine (DAQ), piperaquine (PQ), naphthoquine (NQ), mefloquine (MQ), LM, dihydroartemisinin and azithromycin (AZ)]. RESULTS: The geometric mean (95% confidence interval) concentration required to inhibit parasite growth by 50% (IC(50)) was 167 (141-197) nM for CQ, and 82% of strains were resistant (threshold 100 nM), consistent with near-fixation of the CQ resistance-associated pfcrt allele in PNG. Except for AZ [8.351 (5.418-12.871) nM], the geometric mean IC(50) for the other drugs was <20 nM. There were strong associations between the IC(50)s of 4-aminoquinoline (CQ, AQ, DAQ and NQ), bisquinoline (PQ) and aryl aminoalcohol (MQ) compounds suggesting cross-resistance, but LM IC(50) only correlated with that of MQ. Conclusions Most PNG isolates are resistant to CQ in vitro but not to other ACT partner drugs. The non-isotopic semi-automated high-throughput nature of the Plasmodium lactate dehydrogenase assay facilitates the convenient serial assessment of local parasite sensitivity, so that emerging resistance can be identified with relative confidence at an early stage.

Pharmacokinetic properties of sulfadoxine-pyrimethamine in pregnant women.

To determine the pharmacokinetic disposition of sulfadoxine (SDOX) and pyrimethamine (PYR) when administered as intermittent presumptive treatment during pregnancy (IPTp) for malaria, 30 Papua New Guinean women in the second or third trimester of pregnancy and 30 age-matched nonpregnant women were given a single dose of 1,500 mg of SDOX plus 75 mg of pyrimethamine PYR. Blood was taken at baseline and 1, 2, 4, 6, 12, 18, 24, 30, 48, and 72 h and at 7, 10, 14, 28, and 42 days posttreatment in all women. Plasma samples were assayed for SDOX, N-acetylsulfadoxine (NASDOX), and PYR by high-performance liquid chromatography. Population pharmacokinetic modeling was performed using NONMEM v6.2.0. Separate user-defined mamillary models were fitted to SDOX/NASDOX and PYR. When the covariate pregnancy was applied to clearance, there was a significant improvement in the base model for both treatments. Pregnancy was associated with a significantly lower area under the concentration-time curve from 0 to infinity for SDOX (22,315 versus 33,284 mg x h/liter), NASDOX (801 versus 1,590 mg x h/liter), and PYR (72,115 versus 106,065 microg x h/liter; P < 0.001 in each case). Because lower plasma concentrations of SDOX and PYR could compromise both curative efficacy and posttreatment prophylaxis in pregnant patients, IPTp regimens incorporating higher mg/kg doses than those recommended for nonpregnant patients should be considered.

Respiratory viruses in adults hospitalised with Community-Acquired Pneumonia during the non-winter months in Melbourne: Routine diagnostic practice may miss large numbers of influenza and respiratory syncytial virus infections.

Background: Community-Acquired Pneumonia (CAP) is one of the highest health burden conditions in Australia. Disease notifications and other data from routine diagnosis suffers from selection bias that may misrepresent the true contribution of various aetiological agents. However existing Australian prospective studies of CAP aetiology have either under-represented elderly patients, not utilised Polymerase Chain Reaction (PCR) diagnostics or been limited to winter months. We therefore sought to re-evaluate CAP aetiology by systematically applying multiplex PCR in a representative cohort of mostly elderly patients hospitalised in Melbourne during non-winter months and compare diagnostic results with those obtained under usual conditions of care. Methods: Seventy two CAP inpatients were prospectively enrolled over 2 ten-week blocks during non-winter months in Melbourne in 2016-17. Nasopharyngeal and oropharyngeal swabs were obtained at admission and analysed by multiplex-PCR for 7 respiratory viruses and 5 atypical bacteria. Results: Median age was 74 (interquartile range 67-80) years, with 38 (52.8%) males and 34 (47.2%) females. PCR was positive in 24 (33.3%), including 12 Picornavirus (50.5% of those with a virus), 4 RSV (16.7%) and 4 influenza A (16.7%). CAP-Sym questionnaire responses were similar in those with and without viral infections. Most (80%) pathogens detected by the study, including all 8 cases of influenza and RSV, were not otherwise detected by treating clinicians during hospital admission. Conclusion: One third of patients admitted with CAP during non-winter months had PCR-detectable respiratory viral infections, including many cases of influenza and RSV that were missed by existing routine clinical diagnostic processes.

Patient-reported outcome measurement in community-acquired pneumonia: feasibility of routine application in an elderly hospitalized population.

BACKGROUND: Community-acquired pneumonia (CAP) is a leading cause of morbidity and mortality worldwide, but few studies have evaluated the feasibility of routine patient-reported outcome measures (PROMs) in this illness. This study investigates the feasibility and limitations of three credible PROM instruments in a representative hospitalized cohort to identify potential barriers to routine application. METHODS: A sample of multimorbid hospitalized subjects meeting a standardized CAP definition was recruited. Demographic and clinical data of those able and unable to participate in PROM assessment were compared. The EQ-5D-5L, CAP-Sym 18 Questionnaire, and Late-Life Function and Disability Instrument (LLFDI) were administered (via face-to-face interview) at admission and discharge and (via phone interview or mail) at 30 and 90 days post-discharge. Feasibility measures included the proportion of individuals able to participate in assessment, attrition rates, data completeness, and instrument completion times. Scores at admission and 30 days post-discharge were examined for association with age. RESULTS: Of 82 subjects screened, 44 (54%) participated. Cognitive impairment (n = 12, 15%) commonly precluded participation. Seventeen (39%) participants were lost to follow-up by 90 days. Missing data at item level was negligible for all instruments, regardless of the mode of completion. Completion of the three instruments collectively in a face-to-face interview took a median of 17 min (IQ range 13-21) per participant. The burden of reported symptoms at admission was higher for younger participants aged 18-74 years (mean (standard deviation)) CAP-Sym 18 score at admission 34.2 (18.6) vs. 19.0 (11.3) for those aged ≥ 75 years. CONCLUSIONS: Routine application of PROMs can provide valuable information relating to multiple aspects of clinical recovery for individuals hospitalized with CAP. However, heterogeneous demographic characteristics and complex underlying health status introduce challenges to feasibility and interpretability of these instruments in this population. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02835040.

Transfer of chloroquine and desethylchloroquine across the placenta and into milk in Melanesian mothers.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: The literature on placental and milk transfer of chloroquine and its major bioactive metabolite desethylchloroquine is sparse and incomplete. WHAT THIS STUDY ADDS: We have provided data on the transplacental transfer of chloroquine and desethylchloroquine in Melanesian women (n = 19), measured transfer of these drugs into breast milk (n = 16) and estimated absolute and relative infant doses for the breastfed infant. The data for desethylchloroquine are novel. In all three areas we have significantly increased both quantity and quality of the available database. AIMS: To investigate the transfer of chloroquine and its major bioactive metabolite desethylchloroquine across the placenta and into breast milk. METHODS: In Papua New Guinea, chloroquine (CQ; 25 mg base kg(-1)) is recommended for prophylaxis of malaria during pregnancy, and at the Alexishafen Health Centre women are routinely prescribed CQ at the time of delivery. Fetal-cord and maternal serum samples were collected at delivery (n = 19) and milk samples were collected from day 3 to day 17-21 after delivery (n = 16). CQ and its primary active metabolite desethylchloroquine (DECQ) were quantified by high-performance liquid chromatography. For both CQ and DECQ cord/maternal ratios (C/M) were calculated to characterize placental transfer, and infant exposure via milk was estimated by standard methods. RESULTS: The median (interquartile range) C/M was 1.1 (0.9, 1.6) for CQ and 1.2 (0.5, 1.8) for DECQ. The average concentration in milk over the time of sampling was 167 microg l(-1) (27, 340) for CQ and 54 microg l(-1) (22, 106) for DECQ. Estimated absolute and relative infant doses were 34 microg kg(-1) day(-1) (7, 50) and 15 microg kg(-1) day(-1) (4, 26), and 2.3% (0.5, 3.6) and 1.0% (0.4, 2.0) for CQ and DECQ (as CQ equivalents), respectively. CONCLUSION: Infant exposure to CQ and DECQ during pregnancy will be similar to that in the maternal circulation, and dependent on maternal dose and frequency. The median CQ + DECQ relative infant dose of 3.2% (as CQ equivalents) was low, confirming that use of CQ during lactation is compatible with breastfeeding.

Toxicology and pharmacokinetics of piperaquine in mice.

Pharmacokinetic and toxicological data for piperaquine (PQ) - a bisquinoline antimalarial drug - are limited, despite strong evidence of clinical efficacy. Our aim was to conduct a detailed toxicological investigation of PQ in Swiss mice. The study comprised three phases: (i) oral PQ phosphate (PQP) at doses ranging from 0 to 600 mg/(kg day) for 5 days. Pathology tests included haematological and biochemical indices, and histopathology of the liver, heart and kidneys. (ii) PQP doses of 0-300 mg/(kg day) for 12 days and pathology tests as described. (iii) Pharmacokinetic parameters determined from mice given 100mg/(kg day) PQP for 5 days. Blood was harvested from mice over 56 days and plasma analysed by HPLC. Mice given low doses of PQ had stable, normal body and organ weights. Weight loss was observed in mice given high doses and was accompanied by increased liver and kidney weights. Principal haematological effects were modest fluctuations in total white cells and neutrophils; biochemical effects were elevated ALT and low albumin in high-dose groups. Liver histopathology revealed minor cytoplasmic and inflammatory effects. PQ treatment did not affect heart muscle but minor renal changes were observed at high doses. Pharmacokinetic parameters were consistent with previous studies: t1/2, CL and V were 16 days, 1.36 L/(h kg) and 756 L/kg, respectively. PQ may cause minor hepatotoxicity and renal tubular cell damage, and adversely affect selected haematological indices, as demonstrated at cumulative doses approximately 50 times those recommended in humans. Significant effects in humans will likely be infrequent and dose-related.

Caregivers' acceptance of using artesunate suppositories for treating childhood malaria in Papua New Guinea.

Community-based interventions using artemisinin-derived suppositories may potentially reduce malaria-related childhood mortality. However, their sociocultural acceptability is unknown in Papua New Guinea and a formal examination of caregiver's attitudes to rectal administration was needed to inform effective deployment strategies. Caregivers (n = 131) of children with uncomplicated malaria were questioned on their prior experience with, and attitudes to, rectal administration and then offered artesunate suppositories as treatment of their child. The 29% who refused this alternative were further questioned to determine their reasons for this refusal. Lack of spousal approval and fear of side effects were the most common reasons for refusal. Sixty-six percent of caregivers agreed to self-administer suppositories, which were perceived as effective (99%), safe (96%), and fast-acting (91%), but problematic to administer to a struggling child (56%). Shame, embarrassment, and hygiene were not significant concerns. Acceptability of rectal administration should be relatively high in Papua New Guinea. However, deployment must be accompanied by health education that addresses the practical aspects of administration, is appropriate for the illiterate, and is directed at fathers as well as mothers.

Rectal administration of artemisinin derivatives for the treatment of malaria.

CONTEXT: Rectal administration of artemisinin derivatives is a potentially lifesaving emergency treatment of severe malaria. Many different preparations are marketed in tropical countries, but their pharmacokinetic disposition and clinical efficacy may vary. OBJECTIVE: To review the pharmacokinetics, efficacy, and safety of rectally administered artesunate, artemisinin, dihydroartemisinin, and artemether. DATA SOURCES: We searched the MEDLINE, EMBASE, Cochrane Database of Clinical Reviews, Global Health, Web of Science, and CINAHL computerized databases up to December 2006, along with reviewing unpublished data from conference proceedings, pharmaceutical companies, and regulatory applications. Studies in languages other than English were translated. STUDY SELECTION: Studies were included involving rectal administration of an artemisinin derivative to healthy volunteers or patients with measurement of plasma drug concentrations or rates of initial parasite clearance. Both single-arm and comparative trials were included. DATA EXTRACTION: Forty-five studies were identified, of which 39 eligible studies were included in the review. Primary efficacy outcome measures included parasite density as a percentage of baseline at 12 and 24 hours following the first dose. Pharmacokinetic variables included maximum plasma concentration (C(max)), time to C(max) (T(max)), and area under the plasma concentration-time curve. Weighted means were calculated from available data. DATA SYNTHESIS: Thirty-two studies provided valid clinical efficacy data: 19 of artesunate, 10 of artemisinin, 2 of dihydroartemisinin, and 1 of artemether. All demonstrated prompt parasite clearance, with evidence of a dose-dependent effect for artesunate. Mortality rates in severe malaria (weighted means, 0%-13%) were consistent with those expected. Eight studies compared rectal artemisinin with conventional parenteral treatment (quinine, artemether, or artesunate) for severe malaria. Despite similar clinical outcomes, rectal artemisinin derivatives initiated parasite clearance more rapidly than parenteral treatment (percentage of baseline at 12 hours, < or =27% vs > or =56%, respectively). Eighteen pharmacokinetic studies were identified, including 13 of artesunate. There was marked interindividual variability in most pharmacokinetic variables, but artesunate achieved an earlier T(max) and higher C(max) and area under the plasma concentration-time curve than other artemisinin derivatives. CONCLUSIONS: Available rectal preparations of artemisinin derivatives differ in their pharmacokinetic disposition. Most available evidence pertains to artesunate and artemisinin. Despite marked interindividual variability in bioavailability, rectal preparations appear to have acceptable therapeutic efficacy, including in severe illness.

Optimal antimalarial dose regimens for chloroquine in pregnancy based on population pharmacokinetic modelling.

Despite extensive use and accumulated evidence of safety, there have been few pharmacokinetic studies from which appropriate chloroquine (CQ) dosing regimens could be developed specifically for pregnant women. Such optimised CQ-based regimens, used as treatment for acute malaria or as intermittent preventive treatment in pregnancy (IPTp), may have a valuable role if parasite CQ sensitivity returns following reduced drug pressure. In this study, population pharmacokinetic/pharmacodynamic modelling was used to simultaneously analyse plasma concentration-time data for CQ and its active metabolite desethylchloroquine (DCQ) in 44 non-pregnant and 45 pregnant Papua New Guinean women treated with CQ and sulfadoxine/pyrimethamine or azithromycin (AZM). Pregnancy was associated with 16% and 49% increases in CQ and DCQ clearance, respectively, as well as a 24% reduction in CQ relative bioavailability. Clearance of DCQ was 22% lower in those who received AZM in both groups. Simulations based on the final multicompartmental model demonstrated that a 33% CQ dose increase may be suitable for acute treatment for malaria in pregnancy as it resulted in equivalent exposure to that in non-pregnant women receiving recommended doses, whilst a double dose would likely be required for an effective duration of post-treatment prophylaxis when used as IPTp especially in areas of CQ resistance. The impact of co-administered AZM was clinically insignificant in simulations. The results of past/ongoing trials employing recommended adult doses of CQ-based regimens in pregnant women should be interpreted in light of these findings, and consideration should be given to using increased doses in future trials.

Piperaquine: a resurgent antimalarial drug.

Piperaquine is a bisquinoline antimalarial drug that was first synthesised in the 1960s, and used extensively in China and Indochina as prophylaxis and treatment during the next 20 years. A number of Chinese research groups documented that it was at least as effective as, and better tolerated than, chloroquine against falciparum and vivax malaria, but no pharmacokinetic characterisation was undertaken. With the development of piperaquine-resistant strains of Plasmodium falciparum and the emergence of the artemisinin derivatives, its use declined during the 1980s. However, during the next decade, piperaquine was rediscovered by Chinese scientists as one of a number of compounds suitable for combination with an artemisinin derivative. The rationale for such artemisinin combination therapies (ACTs) was to provide an inexpensive, short-course treatment regimen with a high cure rate and good tolerability that would reduce transmission and protect against the development of parasite resistance. This approach has now been endorsed by the WHO. Piperaquine-based ACT began as China-Vietnam 4 (CV4): dihydroartemisinin [DHA], trimethoprim, piperaquine phosphate and primaquine phosphate), which was followed by CV8 (the same components as CV4 but in increased quantities), Artecom (in which primaquine was omitted) and Artekin or Duo-Cotecxin (DHA and piperaquine phosphate only). Recent Indochinese studies have confirmed the excellent clinical efficacy of piperaquine-DHA combinations (28-day cure rates >95%), and have demonstrated that currently recommended regimens are not associated with significant cardiotoxicity or other adverse effects. The pharmacokinetic properties of piperaquine have also been characterised recently, revealing that it is a highly lipid-soluble drug with a large volume of distribution at steady state/bioavailability, long elimination half-life and a clearance that is markedly higher in children than in adults. The tolerability, efficacy, pharmacokinetic profile and low cost of piperaquine make it a promising partner drug for use as part of an ACT.

Safety and therapeutic efficacy of artesunate suppositories for treatment of malaria in children in Papua New Guinea.

BACKGROUND: Although suppositories of artemisinin derivatives may be a valuable option for treatment of malaria in children when circumstances prevent oral and parenteral therapy, few confirmatory data have been published. METHODS: We assessed the safety and efficacy of rectal artesunate in 47 children ages 5 to 10 years with uncomplicated malaria acquired in a hyperendemic area of Papua New Guinea. Thirty were symptomatic and had Plasmodium falciparum parasitemia >2000/microl (Group 1), 12 had and either a parasitemia <2000/microl or minimal/no symptoms (Group 2) and 5 had Plasmodium vivax (Group 3). Each child received rectal artesunate 10 to 15 mg/kg at 0 and 12 h. After monitoring for 24 h, chloroquine plus sulfadoxine/pyrimethamine was given, and the patient discharged. RESULTS: Artesunate suppositories were well-tolerated. After 24 h only one child (from Group 1) had persistent parasitemia, and only one (from Group 3) had not defervesced. These two children received intramuscular quinine and recovered uneventfully. Three Group 2 children redeveloped fever and tachycardia at 24 h, but each responded to simple supportive measures and remained aparasitemic. CONCLUSIONS: Intrarectal artesunate is safe, effective initial treatment for uncomplicated malaria in children. A transient fever spike can sometimes occur after parasite clearance. We recommend that children with uncomplicated malaria receive two doses of > or =10 mg/kg rectal artesunate within the first 24 h.