Neurotoxicity in animals due to arteether and artemether

Artemisinins and their impact on inhibitory neurotransmission

Artemisinin, a major extract of the annual mugwort Artemisia annua, and its semisynthetic derivatives represent state-of-the-art antimalarial drugs. These compounds also target, via poorly understood mechanisms, various mammalian pathways, thereby exhibiting anticancer and immunomodulatory properties. Recently, crystal structures of artemisinins with two mammalian targets were determined, namely, gephyrin, the prime scaffolding protein at inhibitory postsynapses, and pyridoxal kinase, a central metabolic enzyme synthesizing vitamin B6. These structures and corresponding functional studies demonstrate that artemisinins play a dual role in modulating inhibitory synapses, acting on postsynaptic sites by impeding inhibitory neurotransmitter receptor clustering and on presynaptic terminals by limiting the biosynthesis of the inhibitory neurotransmitter γ-aminobutyric acid. These studies pave the way for further investigations of artemisinins as inhibitory neurotransmission modulators in humans.

Parenteral artemisinins are associated with reduced mortality and neurologic deficits and improved long-term behavioral outcomes in children with severe malaria

BACKGROUND

In 2011, the World Health Organization recommended injectable artesunate as the first-line therapy for severe malaria (SM) due to its superiority in reducing mortality compared to quinine. There are limited data on long-term clinical and neurobehavioral outcomes after artemisinin use for treatment of SM.

METHODS

From 2008 to 2013, 502 Ugandan children with two common forms of SM, cerebral malaria and severe malarial anemia, were enrolled in a prospective observational study assessing long-term neurobehavioral and cognitive outcomes following SM. Children were evaluated a week after hospital discharge, and 6, 12, and 24 months of follow-up, and returned to hospital for any illness. In this study, we evaluated the impact of artemisinin derivatives on survival, post-discharge hospital readmission or death, and neurocognitive and behavioral outcomes over 2 years of follow-up.

RESULTS

346 children received quinine and 156 received parenteral artemisinin therapy (artemether or artesunate). After adjustment for disease severity, artemisinin derivatives were associated with a 78% reduction in in-hospital mortality (adjusted odds ratio, 0.22; 95% CI, 0.07-0.67). Among cerebral malaria survivors, children treated with artemisinin derivatives also had reduced neurologic deficits at discharge (quinine, 41.7%; artemisinin derivatives, 23.7%, p=0.007). Over a 2-year follow-up, artemisinin derivatives as compared to quinine were associated with better adjusted scores (negative scores better) in internalizing behavior and executive function in children irrespective of the age at severe malaria episode. After adjusting for multiple comparisons, artemisinin derivatives were associated with better adjusted scores in behavior and executive function in children <6 years of age at severe malaria exposure following adjustment for child age, sex, socioeconomic status, enrichment in the home environment, and the incidence of hospitalizations over follow-up. Children receiving artesunate had the greatest reduction in mortality and benefit in behavioral outcomes and had reduced inflammation at 1-month follow-up compared to children treated with quinine.

CONCLUSIONS

Treatment of severe malaria with artemisinin derivatives, particularly artesunate, results in reduced in-hospital mortality and neurologic deficits in children of all ages, reduced inflammation following recovery, and better long-term behavioral outcomes. These findings suggest artesunate has long-term beneficial effects in children surviving severe malaria.

Ototoxic hearing loss from antimalarials: A systematic narrative review

BACKGROUND

Drugs used in curative and prophylactic antimalarial treatment may be ototoxic and lead to permanent hearing loss, but there is no consensus regarding prevalence and permanence of ototoxic hearing loss caused by antimalarials. The purpose of this systematic narrative review was to synthesize current evidence on antimalarial ototoxicity in human populations.

METHOD

Studies published between 2005 and 2018 that reported prevalence of post-treatment hearing loss in individuals treated for malaria were included.

RESULTS

Twenty-two studies including data from 21 countries were included. Primary themes of the included studies were to evaluate drug safety and/or efficacy (n = 13) or ototoxic effects of drugs (n = 9). Hearing data were measured objectively in 9 studies. Five studies focused on quinine (or derivates), 10 focused on artemisinin combination therapies, and 7 considered multiple drug combinations. There is a paucity of evidence that thoroughly reports potentially permanent ototoxic effects of antimalarials.

CONCLUSIONS

Antimalarial drugs may be ototoxic in some cases. More research in human populations is needed to describe ototoxicity of current antimalarials and of future drugs that will be used/developed in response to antimalarial resistance. It is recommended that randomized trials evaluating drug safety objectively measure and report ototoxic hearing loss as an adverse event.

Longitudinal study based on a safety registry for malaria patients treated with artenimol-piperaquine in six European countries

Background

European travellers to endemic countries are at risk of malaria and may be affected by a different range of co-morbidities than natives of endemic regions. The safety profile, especially cardiac issues, of artenimol (previously dihydroartemisinin)–piperaquine (APQ) Eurartesim^® during treatment of uncomplicated imported falciparum malaria is not adequately described due to the lack of longitudinal studies in this population. The present study was conducted to partially fill this gap.

Methods

Participants were recruited through Health Care Provider’s safety registry in 15 centres across 6 European countries in the period 2013–2016. Adverse events (AE) were collected, with a special focus on cardiovascular safety by including electrocardiogram QT intervals evaluated after correction with either Bazett’s (QTcB) or Fridericia’s (QTcF) methods, at baseline and after treatment. QTcB and/or QTcF prolongation were defined by a value > 450 ms for males and children and > 470 ms for females.

Results

Among 294 participants, 30.3% were women, 13.7% of Caucasian origin, 13.5% were current smoker, 13.6% current alcohol consumer and 42.2% declared at least one illness history. The mean (SD) age and body mass index were 39.8 years old (13.2) and 25.9 kg/m² (4.7). Among them, 75 reported a total of 129 AE (27 serious), 46 being suspected to be related to APQ (11 serious) and mostly labelled as due to haematological, gastrointestinal, or infection. Women and Non-African participants had significantly (p < 0.05) more AEs. Among AEs, 21 were due to cardiotoxicity (7.1%), mostly QT prolongation, while 6 were due to neurotoxicity (2.0%), mostly dizziness. Using QTcF correction, QT prolongation was observed in 17/143 participants (11.9%), only 2 of them reporting QTcF > 500 ms (milliseconds) but no clinical symptoms. Using QTcB correction increases of > 60 ms were present in 9 participants (6.3%). A trend towards increased prolongation was observed in those over 65 years of age but only a few subjects were in this group. No new safety signal was reported. The overall efficacy rate was 255/257 (99.2%).

Conclusions

APQ appears as an effective and well-tolerated drug for treatment of malaria in patients recruited in European countries. AEs and QT prolongation were in the range of those obtained in larger cohorts from endemic countries.

Trial registration This study has been registered in EU Post-Authorization Studies Register as EUPAS6942

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03750-x.

Efficacy and safety of artemisinin-based combination therapies for the treatment of uncomplicated malaria in pediatrics: a systematic review and meta-analysis

BACKGROUND

Malaria is a major cause of morbidity and mortality in pediatrics in malaria endemic areas. Artemisinin-based combination therapies (ACTs) are the drugs of choice for malaria management particularly across malaria-endemic countries. This systematic review and meta-analysis was performed to assess efficacy and safety of ACTs for uncomplicated malaria in pediatric populations.

METHODS

A body of evidence was searched for published ACT trials until March 06, 2020. The search was focused on efficacy and safety studies of ACTs for uncomplicated malaria in pediatrics. PubMed library was searched using best adapted search terms after multiple trials. References were exported to the endnote library and then to Covidence for screening. Data was extracted using the Covidence platform. The per-protocol analysis report for the efficacy and the intention-to-treat analysis for the safety were synthesized. Met-analysis was carried using Open Meta-Analyst software. Random effects model was applied and the heterogeneity of studies was evaluated using I2 statistic.

RESULTS

Nineteen studies were included in the final analysis. Overall, crude, PCR-corrected P. falciparum malaria treatment success rate was 96.3 and 93.9% for day 28 and 42, respectively. In the subgroup analysis, PCR-corrected adequate clinical and parasitological response (ACPR) of dihydroartemisinin-piperaquine (DP) was 99.6% (95% CI: 99.1 to 100%, I2 = 0%; 4 studies) at day 28 and 99.6% (95% CI of 99 to 100%, I2 = 0%; 3 studies) at day 42. Nine studies reported ACT related adverse drug reactions (ADR) (8.3%, 356/4304). The reported drug related adverse reactions ranged from 1.8% in DP (two studies) to 23.3% in artesunate-pyronaridine (AP). Gastrointestinal symptoms were the most common ACT related adverse effects, and all ADRs were reported to resolve spontaneously.

CONCLUSION

ACTs demonstrated a high crude efficacy and tolerability against P. falciparum. The high treatment success and tolerability with low heterogeneity conferred by DP has implication for policy makers who plan the use of ACTs for uncomplicated falciparum malaria treatment in pediatrics.

Piperaquine Exposure Is Altered by Pregnancy, HIV, and Nutritional Status in Ugandan Women

Dihydroartemisinin-piperaquine (DHA-PQ) provides highly effective therapy and chemoprevention for malaria in pregnant African women. PQ concentrations of >10.3 ng/ml have been associated with reduced maternal parasitemia, placental malaria, and improved birth outcomes. We characterized the population pharmacokinetics (PK) of PQ in a post hoc analysis of human immunodeficiency virus (HIV)-infected and -uninfected pregnant women receiving DHA-PQ as chemoprevention every 4 or 8 weeks. The effects of covariates such as pregnancy, nutritional status (body mass index [BMI]), and efavirenz (EFV)-based antiretroviral therapy were investigated. PQ concentrations from two chemoprevention trials were pooled to create a population PK database from 274 women and 2,218 PK observations. A three-compartment model with an absorption lag best fit the data. Consistent with our prior intensive PK evaluation, pregnancy and EFV use resulted in a 72% and 61% increased PQ clearance, compared to postpartum and HIV-uninfected pregnant women, respectively. Low BMI at 28 weeks of gestation was associated with increased clearance (2% increase per unit decrease in BMI). Low-BMI women given DHA-PQ every 8 weeks had a higher prevalence of parasitemia, malaria infection, and placental malaria compared to women with higher BMIs. The reduced piperaquine exposure in women with low BMI as well as during EFV coadministration, compared to pregnant women with higher BMIs and not taking EFV, suggests that these populations could benefit from weekly instead of monthly dosing for prevention of malaria parasitemia. Simulations indicated that because of the BMI-clearance relationship, weight-based regimens would not improve protection compared to a 2,880 mg fixed-dose regimen when provided monthly. (The clinical trials described in this paper have been registered at ClinicalTrials.gov under identifiers NCT02163447 and NCT02282293.).

Molecular targets in cerebral malaria for developing novel therapeutic strategies

Cerebral malaria (CM) is the severe neurological complication associated with Plasmodium falciparum infection. In clinical settings CM is predominantly characterized by fever, epileptic seizures, and asexual forms of parasite on blood smears, coma and even death. Cognitive impairment in the children and adults even after survival is one of the striking consequences of CM. Poor diagnosis often leads to inappropriate malaria therapy which in turn progress into a severe form of disease. Activation of multiple cell death pathways such as Inflammation, oxidative stress, apoptosis and disruption of blood brain barrier (BBB) plays critical role in the pathogenesis of CM and secondary brain damage. Thus, understanding such mechanisms of neuronal cell death might help to identify potential molecular targets for CM. Mitigation strategies for mortality rate and long-term cognitive deficits caused by existing anti-malarial drugs still remains a valid research question to ask. In this review, we discuss in detail about critical neuronal cell death mechanisms and the overall significance of adjunctive therapy with recent trends, which provides better insight towards establishing newer therapeutic strategies for CM.

Current scenario of artemisinin and its analogues for antimalarial activity

Human malaria, one of the most striking, reemerging infectious diseases, is caused by several types of Plasmodium parasites. Whilst advances have been made in lowering the numbers of cases and deaths, it is clear that a strategy based solely on disease control year on year, without reducing transmission and ultimately eradicating the parasite, is unsustainable. Natural products have served as a template for the design and development of antimalarial drugs currently in the clinic or in the development phase. Artemisinin combine potent, rapid antimalarial activity with a wide therapeutic index and an absence of clinically important resistance. The alkylating ability of artemisinin and its semi-synthetic analogues toward heme related to their antimalarial efficacy are underlined. Although impressive results have already been achieved in malaria research, more systematization and concentration of efforts are required if real breakthroughs are to be made. This review will concisely cover the clinical, preclinical antimalarial and current updates in artemisinin based antimalarial drugs. Diverse classes of semi-synthetic analogs of artemisinin reported in the last decade have also been extensively studied. The experience gained in this respect is discussed.

Antimalarial Activity of C-10 Substituted Triazolyl Artemisinin

We synthesized C-10 substituted triazolyl artemisinins by the Huisgen cycloaddition reaction between dihydroartemisinins (2) and variously substituted 1, 2, 3-triazoles (8a-8h). The antimalarial activities of 32 novel artemisinin derivatives were screened against a chloroquine-resistant parasite. Among them, triazolyl artemisinins with electron-withdrawing groups showed stronger antimalarial activities than those shown by the derivatives having electron-donating groups. In particularly, m-chlorotriazolyl artemisinin (9d-12d) showed antimalarial activity equivalent to that of artemisinin and could be a strong drug candidate.

Antimalarial drugs and the prevalence of mental and neurological manifestations: A systematic review and meta-analysis

Background: Antimalarial drugs affect the central nervous system, but it is difficult to differentiate the effect of these drugs from that of the malaria illness. We conducted a systematic review to determine the association between anti-malarial drugs and mental and neurological impairment in humans.  Methods: We systematically searched online databases, including Medline/PubMed, PsychoInfo, and Embase, for articles published up to 14th July 2016. Pooled prevalence, heterogeneity and factors associated with prevalence of mental and neurological manifestations were determined using meta-analytic techniques.  Results: Of the 2,349 records identified in the initial search, 51 human studies met the eligibility criteria. The median pooled prevalence range of mental and neurological manifestations associated with antimalarial drugs ranged from 0.7% (dapsone) to 48.3% (minocycline) across all studies, while it ranged from 0.6% (pyrimethamine) to 42.7% (amodiaquine) during treatment of acute malaria, and 0.7% (primaquine/dapsone) to 55.0% (sulfadoxine) during prophylaxis. Pooled prevalence of mental and neurological manifestations across all studies was associated with an increased number of antimalarial drugs (prevalence ratio= 5.51 (95%CI, 1.05-29.04); P=0.045) in a meta-regression analysis. Headaches (15%) and dizziness (14%) were the most common mental and neurological manifestations across all studies. Of individual antimalarial drugs still on the market, mental and neurological manifestations were most common with the use of sulphadoxine (55%) for prophylaxis studies and amodiaquine (42.7%) for acute malaria studies. Mefloquine affected more domains of mental and neurological manifestations than any other antimalarial drug.  Conclusions: Antimalarial drugs, particularly those used for prophylaxis, may be associated with mental and neurological manifestations, and the number of antimalarial drugs taken determines the association. Mental and neurological manifestations should be assessed following the use of antimalarial drugs.

Antimalarial drugs and the prevalence of mental and neurological manifestations: A systematic review and meta-analysis

Background: Antimalarial drugs affect the central nervous system, but it is difficult to differentiate the effect of these drugs from that of the malaria illness. We conducted a systematic review to determine the association between anti-malarial drugs and mental and neurological impairment in humans.  Methods: We systematically searched online databases, including Medline/PubMed, PsychoInfo, and Embase, for articles published up to 14th July 2016. Pooled prevalence, heterogeneity and factors associated with prevalence of mental and neurological manifestations were determined using meta-analytic techniques.  Results: Of the 2,349 records identified in the initial search, 51 human studies met the eligibility criteria. The median pooled prevalence range of mental and neurological manifestations associated with antimalarial drugs ranged from 0.7% (dapsone) to 48.3% (minocycline) across all studies, while it ranged from 0.6% (pyrimethamine) to 42.7% (amodiaquine) during treatment of acute malaria, and 0.7% (primaquine/dapsone) to 55.0% (sulfadoxine) during prophylaxis. Pooled prevalence of mental and neurological manifestations across all studies was associated with an increased number of antimalarial drugs (prevalence ratio= 5.51 (95%CI, 1.05-29.04); P=0.045) in a meta-regression analysis. Headaches (15%) and dizziness (14%) were the most common mental and neurological manifestations across all studies. Of individual antimalarial drugs still on the market, mental and neurological manifestations were most common with the use of sulphadoxine (55%) for prophylaxis studies and amodiaquine (42.7%) for acute malaria studies. Mefloquine affected more domains of mental and neurological manifestations than any other antimalarial drug.  Conclusions: Antimalarial drugs, particularly those used for prophylaxis, may be associated with mental and neurological manifestations, and the number of antimalarial drugs taken determines the association. Mental and neurological manifestations should be assessed following the use of antimalarial drugs.

Safety of Artemisinin-Based Combination Therapies in Nigeria: A Cohort Event Monitoring Study

BACKGROUND

A pilot programme of Cohort Event Monitoring (CEM) was conducted across the six geopolitical zones of Nigeria on patients treated for uncomplicated malaria with artemisinin-based combination therapy (ACT). The emergence and spread of malaria parasites resistant to commonly available antimalarial drugs necessitated a shift in policy for malaria treatment by the Federal Government from the use of chloroquine and sulphadoxine-pyrimethamine (SP) as first-line treatments to ACTs. Initial reports following deployment of ACTs in clinical settings raised safety concerns regarding their use. Although artemisinin and its derivatives are generally thought to be safe, there are currently few or no data on their safety among populations in Nigeria.

OBJECTIVES

The main objectives of the CEM programme were to proactively determine the adverse event (AE) profile of artesunate/amodiaquine (AA) and artemether/lumefantrine (AL) in real-life settings and to find out the factors predisposing to AEs.

METHODS

The CEM study was observational, longitudinal, prospective, and inceptional. Patients were observed in real-life situations. It was conducted in six public health facilities in Nigeria on patients with a clinical diagnosis of uncomplicated malaria treated with ACTs. Patients were prescribed one of the ACTs on an alternate basis as they enrolled into the programme. Follow-up reviews were undertaken on days 3 and 7 following commencement of ACT treatment. At follow-up, patients were evaluated for any clinical event that they might have experienced following the use of the ACTs. We report the result of this initial pilot in which 3,010 patients treated for uncomplicated malaria with AA or AL were enrolled.

RESULTS

The seven most common AEs seen were general body weakness 25.0/36.6% (AL/AA); dizziness 11.9/17.2% (AL/AA); vomiting 8.0/10.2% (AL/AA); abdominal pain 8.5/7.2% (AL/AA); insomnia 6.3/5.9% (AL/AA); body pains 3.4/5.2 (AL/AA) %; anorexia 8.5/4.6% (AL/AA). Most adverse events occurred from day 1 and peaked by day 2 and 3 of medication with the mean duration of events being 3 days. By the end of the follow-up visit on day 7, the AEs had resolved in the majority of patients. Adverse events were more common in the AA group than AL revealing a better safety profile for AL (p < 0.001). Both ACTs demonstrated good ability to resolve the clinical symptoms of uncomplicated malaria.

CONCLUSION

In conclusion, this pilot CEM programme suggests that adverse events with ACTs were common. However, serious life-threatening events were not common. It appears that ACTs have a tolerable safety profile among Nigerians.

Anorectic Toxicity of Dih Ydroartemisinin, Artemether, and Arteether in Rats Following Multiple Intramuscular Doses

During studies of arteether (AE), artemether (AM), and dihydroartemisinin (DQHS) neurotoxicity, the effect of 7 daily intramuscular doses (25, 50, and 100 mg/ kg/d) of those antimalarial drugs on gastrointestinal function was investigated in rats. A modified Nichols' method was used to measure daily food and water consumption. To estimate gastric transit, the total length amaranth (administered 40 minutes prior to sacrifice) dye traveled through small intestine were measured, and to determine gastric retention, the tied-off stomach pouch was removed and the contents weighed 24 hours after the last dose or when a rat became moribund or died. AM and AE dose solutions were prepared using sesame oil, whereas 50% dimethylacetamide (DMAC) sesame oil was used for DQHS. The results showed that after dosing with 50 mg/ kg for 7 days, 50% inhibition of food consumption (ID50) occurred at 1.9 days for DQHS, 3.9 days for AM, and 4.1 days for AE. Similar data were observed for water intake. After 100 mg/kg dosing, the ID50 s for food and water consumption decreased to 2.8-2.9 days for AM and 3.1-3.7 days for AE. Food consumption and body weights were decreased following all three treatments, and rats exhibited neurologic symptoms at 25-100 mg/kg dose of DQHS and 50-100 mg/kg dose of AM and AE. In addition, the results constituted a 53% and 82% inhibition of gastric transit for AM and AE, respectively, at 25 mg/kg animals compared to control, and 100% inhibition was found in high doses (50 and 100 mg/kg) for all the three drugs. The gastric retention ratio (controls equal 1.0) was 26.0 for DQHS, 5.8 with AE, and 2.3 for AM rats following 50 mg/kg dosing. When the 100 mg/kg dose was administered, the gastric retention ratio doubled for AE (11.6) and AM (4.3). The consumption data indicated that DQHS was about 2-3 times more toxic to the anorexia than AM and AE at 25 and 50 mg/kg/day dose levels. Significant differences in gastric emptying and gastric transit activities between AE and AM were observed. Data demonstrated that after multiple intramuscular doses of DQHS, AM, or AE in rats, food consumption and gastric emptying were decreased, gastric transit was inhibited, as reflected in a significant body weight reduction and death. Since an exhibition of the anorectic symptoms of AM and AE was at a lower dose than the neurologic signs in rats, the anorexia could be an early portent or prediction of the neurotoxicity in animals or humans.

Methylene Homologues of Artemisone: An Unexpected Structure-Activity Relationship and a Possible Implication for the Design of C10-Substituted Artemisinins

We sought to establish if methylene homologues of artemisone are biologically more active and more stable than artemisone. The analogy is drawn with the conversion of natural O- and N-glycosides into more stable C-glycosides that may possess enhanced biological activities and stabilities. Dihydroartemisinin was converted into 10β-cyano-10-deoxyartemisinin that was hydrolyzed to the α-primary amide. Reduction of the β-cyanide and the α-amide provided the respective methylamine epimers that upon treatment with divinyl sulfone gave the β- and α-methylene homologues, respectively, of artemisone. Surprisingly, the compounds were less active in vitro than artemisone against P. falciparum and displayed no appreciable activity against A549, HCT116, and MCF7 tumor cell lines. This loss in activity may be rationalized in terms of one model for the mechanism of action of artemisinins, namely the cofactor model, wherein the presence of a leaving group at C10 assists in driving hydride transfer from reduced flavin cofactors to the peroxide during perturbation of intracellular redox homeostasis by artemisinins. It is noted that the carba analogue of artemether is less active in vitro than the O-glycoside parent toward P. falciparum, although extrapolation of such activity differences to other artemisinins at this stage is not possible. However, literature data coupled with the leaving group rationale suggest that artemisinins bearing an amino group attached directly to C10 are optimal compounds.

Application of arteether-loaded polyurethane nanomicelles to induce immune response in breast cancer model

To concentrate a potent anticancer drug (Arteether) in tumor microenvironment, we encapsulated it in biodegradable and pH sensitive polyurethane (PU) nanomicelles (NMs). The nanocomplex was characterized by Fourier transform infrared (FTIR), dynamic light scattering (DLS). The loading capacity and release profile in pH of 5.4 and 7.4 were considered. The cytotoxicity effect was evaluated in vitro and in vivo settings. The level of IFN-γ and IL-4 cytokines of mice splenocytes were assessed by enzyme-linked immunosorbent assay (ELISA). The nanocomplex showed negative zeta charge of -26.2 mV, size of 42.30 nm and high loading capacity (92%). Release profile showed a faster rate of drug liberation at pH 5.4 as compared to that of pH 7.4. It indicated significant inhibitory effect on the growth of 4T1 cell line and increased IFN-γ level.

Severe malaria in children leads to a significant impairment of transitory otoacoustic emissions--a prospective multicenter cohort study

BACKGROUND

Severe malaria may influence inner ear function, although this possibility has not been examined prospectively. In a retrospective analysis, hearing impairment was found in 9 of 23 patients with cerebral malaria. An objective method to quickly evaluate the function of the inner ear are the otoacoustic emissions. Negative transient otoacoustic emissions are associated with a threshold shift of 20 dB and above.

METHODS

This prospective multicenter study analyses otoacoustic emissions in patients with severe malaria up to the age of 10 years. In three study sites (Ghana, Gabon, Kenya) 144 patients with severe malaria and 108 control children were included. All malaria patients were treated with parental artesunate.

RESULTS

In the control group, 92.6 % (n = 108, 95 % confidence interval 86.19-6.2 %) passed otoacoustic emission screening. In malaria patients, 58.5 % (n = 94, malaria vs controls p < 0.001, 95 % confidence interval 48.4-67.9 %) passed otoacoustic emission screening at the baseline measurement. The value increased to 65.2 % (n = 66, p < 0.001, 95 % confidence interval 53.1-75.5 %) at follow up 14-28 days after diagnosis of malaria. The study population was divided into severe non-cerebral malaria and severe malaria with neurological symptoms (cerebral malaria). Whereas otoacoustic emissions in severe malaria improved to a passing percentage of 72.9 % (n = 48, 95 % confidence interval 59-83.4 %) at follow-up, the patients with cerebral malaria showed a drop in the passing percentage to 33 % (n = 18) 3-7 days after diagnosis. This shows a significant impairment in the cerebral malaria group (p = 0.012 at days 3-7, 95 % confidence interval 16.3-56.3 %; p = 0.031 at day 14-28, 95 % confidence interval 24.5-66.3 %).

CONCLUSION

The presented data show that 40 % of children have involvement of the inner ear early in severe malaria. In children, audiological screening after severe malaria infection is not currently recommended, but is worth investigating in larger studies.

Toxicity associated with repeated administration of artemether-lumefantrine in rats

Chemotherapy remains an important approach in the fight against malaria. Artemether-lumefantrine combination is widely in use due to its effectiveness against Plasmodium falciparum. Misuse in the form of multiple repeated doses of this anti-malaria drug is rampant in Nigeria. This study was designed to assess the hepatotoxic and clastogenic potential of extreme misuse of artemether-lumefantrine in rats. Graded doses of artemether-lumefantrine (1-5 mg/kg body weight) were administered by oral gavage for 6 weeks, twice daily, for 3 consecutive days per week. Artemether-lumefantrine, at all doses, did not have significant effects on the body and relative liver weight of treated group compared to the negative control group. The mean γ-glutamyltransferase, alanine, and aspartate aminotransaminase activity in groups of artemether-lumefantrine treated rats were significantly higher (p < 0.05) than that of the negative control group indicating that repeated administration of artemether-lumefantrine may be hepatotoxic. Findings from histological analyses of liver cross-section support the enzyme pattern of hepatoxicity. In addition, the drug, at all experimental doses, significantly induced (p < 0.05) formation of micronucleated polychromatic erythrocytes in the bone marrow cells of the treated rats compared with the negative control indicating clastogenic potential of the drug when misused.

Hematological and biochemical effects of sub-chronic artesunate exposure in rats

Artesunate is a potent and rapidly acting blood schizontocide used to treat chloroquine resistant malaria. Artesunate has been reported to cause embryo, reduced reproductive capacity, hepatotoxicity, neurotoxicity and hematological abnormalities. Previously toxicity studies on artesunate have been done in 2–10 mg/kg dose range mostly for 7 days, scientific studies on sub-chronic exposure of artesunate is not been reported so for. The present study evaluates sub-chronic safety profile of artesunate on 45 days oral administration at 2, 4 and 8 mg/kg/day. Authentication of artesunate has been done by color test, pH, melting point, loss on drying, UV_max, TLC and HPLC study. Artesunate has non-significant effect on liver and kidney weight. Serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), serum alkaline phosphate (ALP), cholesterol (TC), triglyceride (TG), total protein, albumin, bilirubin, creatinine, urea and glucose content were estimated after 45 days treatment along with hematological screening. Artesunate treatment for 45 days significantly increased (p < 0.05–0.001) SGOT, SGPT, ALP, TC, TG, total bilirubin, glucose level at 8 mg/kg/day dose. It has non-significant effect on serum total protein, albumin, creatinine and urea. Hemoglobin, total RBC, platelet, lymphocytes, basophil, mean cell volume and mean corpuscular hemoglobin concentration have not changed but total WBC, neutrophil, eosinophil, packed cell volume and mean cell hemoglobin were increased significantly (p < 0.01) at 8 mg/kg/day dose. Artesunate treatment at 4 and 8 mg/kg/day showed sinusoidal dilation, cytoplasmic vaculation, focal necrosis, sinusoidal congestion and extensive inflammatory changes, whereas kidney was free of any deleterious effect.

Conclusion

Sub-chronic exposure of artesunate at 8 mg/kg/day dose for 45 days period cause hepatic damage along with hematological abnormalities signifying safety concern.

Neuroauditory toxicity of artemisinin combination therapies-have safety concerns been addressed?

Although artemisinin-based combination therapies (ACTs) are widely viewed as safe drugs with a wide therapeutic dose range, concerns about neuroauditory safety of artemisinins arose during their development. A decade ago, reviews of human data suggested a potential neuro-ototoxic effect, but the validity of these findings was questioned. With 5–10 years of programmatic use, emerging artemisinin-tolerant falciparum malaria in southeast Asia, and the first calls to consider an increased dose of artemisinins, we review neuroauditory safety data on ACTs to treat uncomplicated falciparum malaria. Fifteen studies reported a neurological or auditory assessment. The large heterogeneity of neuro-ototoxic end points and assessment methodologies and the descriptive nature of assessments hampered a formal meta-analysis and definitive conclusions, but they highlight the persistent lack of data from young children. This subgroup is potentially most vulnerable to any neuroauditory toxicity because of their development stage, increased malaria susceptibility, and repeated ACT exposure in settings lacking robust safety monitoring.

Subchronic toxicological study of two artemisinin derivatives in dogs

The objective of our study was to profile and compare the systematic changes between orally administered artesunate and intramuscularly injected artemether at a low dose over a 3-month period (92 consecutive days) in dogs. Intramuscular administration of 6 mg kg-1 artemether induced a decreased red blood cell (RBC) count (anemia), concurrent extramedullary hematopoiesis in the spleen and inhibition of erythropoiesis in the bone marrow. We also observed a prolonged QT interval and neuropathic changes in the central nervous system, which demonstrated the cortex and motor neuron vulnerability, but no behavioral changes. Following treatment with artesunate, we observed a decreased heart rate, which was most likely due to cardiac conduction system damage, as well as a deceased RBC count, extramedullary hematopoiesis in the spleen and inhibition of erythropoiesis in the bone marrow. However, in contrast to treatment with artemether, neurotoxicity was not observed following treatment with artesunate. In addition, ultra-structural examination by transmission electron microscopy showed mitochondrial damage following treatment with artesunate. These findings demonstrated the spectrum of toxic changes that result upon treatment with artesunate and artemether and show that the prolonged administration of low doses of these derivatives result in diverse toxicity profiles.

Coartemether (artemether and lumefantrine): an oral antimalarial drug

Coartemether (Riamet, Coartem, Novartis), a tablet formulation of artemether and lumefantrine, is a well-tolerated, fast-acting and effective blood schizontocidal drug that serves primarily in the treatment of uncomplicated falciparum malaria that is resistant to other antimalarials. Initial clinical-parasitological response relies mainly on the artemether component, while lumefantrine effects radical cure. The absorption of lumefantrine is poor during the fasting state, the normal condition in acutely ill malaria patients, but with return to normal diet it becomes adequate. This highlights the need for an appropriate adjustment of the dose regimen. In the area where Plasmodium falciparum shows the highest degree of multidrug resistance worldwide, the best results (99% cure) were obtained with a six-dose regimen given over 5 days. Extensive cardiological investigations have demonstrated the high cardiac safety of coartemether.

General Pharmacology of Artesunate, a Commonly used Antimalarial Drug:Effects on Central Nervous, Cardiovascular, and Respiratory System

Artesunate, a semi-synthetic derivative of artemisinin, is used primarily as a treatment for malaria. Its effects on the central nervous system, general behavior, and cardiovascular, respiratory, and other organ systems were studied using mice, rats, guinea pigs, and dogs. Artesunate was administered orally to mice at doses of 125, 250, and 500 mg/kg and to rats and guinea pigs at 100, 200, and 400 mg/kg. In dogs, test drugs were administered orally in gelatin capsules at doses of 50, 100, and 150 mg/kg. Artesunate induced insignificant changes in general pharmacological studies, including general behavior, motor coordination, body temperature, analgesia, convulsion modulation, blood pressure, heart rate (HR) , and electrocardiogram (ECG) in dogs in vivo; respiration in guinea pigs; and gut motility or direct effects on isolated guinea pig ileum, contractile responses, and renal function. On the other hand, artesunate decreased the HR and coronary flow rate (CFR) in the rat in vitro; however, the extent of the changes was small and they were not confirmed in in vivo studies in the dog. Artesunate increased hexobarbital-induced sleeping time in a dose-related manner. Artesunate induced dose-related decreases in the volume of gastric secretions and the total acidity of gastric contents, and induced increases in pH at a dose of 400 mg/kg. However, all of these changes were observed at doses much greater than clinical therapeutic doses (2.4 mg/kg in humans, when used as an anti-malarial) . Thus, it can be concluded that artesunate is safe at clinical therapeutic doses.

Histological and biochemical effects of arteether™ on the liver of Wistar rats

Arteether™ is among the recent drugs that are used to combat chloroquine-resistant malarial parasites. This study examined the effects of arteether™ on enzyme biomarkers of the liver, serum protein concentrations, and liver morphology. Twenty (20) adult albino Wistar rats weighing 200 - 250 g were randomly divided into four groups (A, B, C and D) of five animals each, and used in this study. Group A rats were given intramuscular (i. m.) arteether™ (3 mg/kg b. w.) daily for 3 days. Group B rats received i. m. arteether™ (6 mg/kg b. w.) daily for 3 days. Group C rats were given i. m. arteether™ (3 mg/kg b. w.) daily for 3 days. The same dose was repeated at two-weekly intervals for 4 further weeks, while group D rats which received normal saline (0.9 % w/ v, 3 ml/kg b.w.), served as controls. At the end of the experiment, the body weights of the animals were determined and recorded. Serum levels of alanine transaminase (ALT), aspartate transaminase (ASP), alkaline phosphatase (ALP), total protein (TP) and albumin were assayed, and histological studies were performed. Results obtained show no significant difference (P<0.05) in liver enzymes (ALT, ASP, ALP). TP and albumin were significantly reduced in group C rats. Histological studies revealed no cyto-architectural changes. It is concluded that at therapeutic doses, arteether™ is well tolerated in Wistar rats.

Neurotoxicity assessment of artemether in juvenile rats

BACKGROUND

Oral administration of artemether in combination with lumefantrine is approved for the treatment of malaria in adults and children. In adult animals, artemether can produce neurotoxicity with intramuscular, but not oral, administration. Herein, the potential of orally administered artemether to produce neurotoxicity in juvenile rats was investigated.

METHODS

In the first study, the toxicity of artemether was evaluated in juvenile rats dosed with 0, 10, 30, and 100mg/kg/day on postpartum days (ppds) 7 to 21. In-life, clinical pathology, anatomic pathology, behavioral, and toxicokinetics evaluations were performed. The second study focused on neurotoxicity during different dosing intervals, with doses of 0, 30, and 80 mg/kg/day on ppds 7 to 13, and doses of 0, 30, and 120 mg/kg/day on ppds 14 to 21, 22 to 28, and 29 to 36. For each dosing interval, in-life, extensive histology, toxicokinetics, and behavioral evaluations were performed. In the third study, toxicokinetics evaluations in the adult were conducted at 20 and 200 mg/kg/day.

RESULTS

The first study demonstrated increased mortality, renal necrosis, and brain hemorrhage at ≥30 mg/kg/day with no persistent effects in surviving animals. In the second study, increased mortality, body weight effects, and a trend toward increased exposure were observed in the ppd 14 and younger animals. Neither specific neurotoxicity nor persistent effects were seen. The toxicokinetic study in adults revealed lower exposures as compared to those in the younger juvenile rats.

CONCLUSIONS

As in the adult rat, oral administration of artemether in the juvenile rat is not associated with the neurotoxicity produced by intramuscular administration.

Reversible audiometric threshold changes in children with uncomplicated malaria

Background. Plasmodium falciparum malaria, as well as certain antimalarial drugs, is associated with hearing impairment in adults. There is little information, however, on the extent, if any, of this effect in children, and the evidence linking artemisinin combination therapies (ACTs) with hearing is inconclusive. Methods. Audiometry was conducted in children with uncomplicated malaria treated with artesunate-amodiaquine (n = 37), artemether-lumefantrine (n = 35), or amodiaquine (n = 8) in Accra, Ghana. Audiometry was repeated 3, 7, and 28 days later and after 9 months. Audiometric thresholds were compared with those of a control group of children (n = 57) from the same area. Findings. During the acute stage, hearing threshold levels of treated children were significantly elevated compared with controls (P < 0.001). The threshold elevations persisted up to 28 days, but no differences in hearing thresholds were evident between treated children and controls after 9 months. The hearing thresholds of children treated with the two ACT regimens were comparable but lower than those of amodiaquine-treated children during acute illness. Interpretation. Malaria is the likely cause of the elevated hearing threshold levels during the acute illness, a finding that has implications for learning and development in areas of intense transmission, as well as for evaluating potential ototoxicity of new antimalarial drugs.

The global pipeline of new medicines for the control and elimination of malaria

Over the past decade, there has been a transformation in the portfolio of medicines to combat malaria. New fixed-dose artemisinin combination therapy is available, with four different types having received approval from Stringent Regulatory Authorities or the World Health Organization (WHO). However, there is still scope for improvement. The Malaria Eradication Research agenda identified several gaps in the current portfolio. Simpler regimens, such as a single-dose cure are needed, compared with the current three-day treatment. In addition, new medicines that prevent transmission and also relapse are needed, but with better safety profiles than current medicines. There is also a big opportunity for new medicines to prevent reinfection and to provide chemoprotection. This study reviews the global portfolio of new medicines in development against malaria, as of the summer of 2012. Cell-based phenotypic screening, and 'fast followers' of clinically validated classes, mean that there are now many new classes of molecules starting in clinical development, especially for the blood stages of malaria. There remain significant gaps for medicines blocking transmission, preventing relapse, and long-duration molecules for chemoprotection. The nascent pipeline of new medicines is significantly stronger than five years ago. However, there are still risks ahead in clinical development and sustainable funding of clinical studies is vital if this early promise is going to be delivered.

Randomized, prospective, three-arm study to confirm the auditory safety and efficacy of artemether-lumefantrine in Colombian patients with uncomplicated Plasmodium falciparum malaria

The safety of artemether-lumefantrine in patients with acute, uncomplicated Plasmodium falciparum malaria was investigated prospectively using the auditory brainstem response (ABR) and pure-tone thresholds. Secondary outcomes included polymerase chain reaction-corrected cure rates. Patients were randomly assigned in a 3:1:1 ratio to either artemether-lumefantrine (N = 159), atovaquone-proguanil (N = 53), or artesunate-mefloquine (N = 53). The null hypothesis (primary outcome), claiming that the percentage of patients with a baseline to Day-7 ABR Wave III latency increase of > 0.30 msec is ≥ 15% after administration of artemether-lumefantrine, was rejected; 2.6% of patients (95% confidence interval: 0.7-6.6) exceeded 0.30 msec, i.e., significantly below 15% (P < 0.0001). A model-based analysis found no apparent relationship between drug exposure and ABR change. In all three groups, average improvements (2-4 dB) in pure-tone thresholds were observed, and polymerase chain reaction-corrected cure rates were > 95% to Day 42. The results support the continued safe and efficacious use of artemether-lumefantrine in uncomplicated falciparum malaria.

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.

Artesunate and artelinic acid: association of embryotoxicity, reticulocytopenia, and delayed stimulation of hematopoiesis in pregnant rats

The artemisinin antimalarials cause embryo death and malformations in animals by killing embryonic erythroblasts. Groups of pregnant rats (N = 4) were administered 35 and 48 µmol/kg artesunate and 17.2, 28.7, 48, 96, and 191 µmol/kg artelinic acid as a single oral dose on gestational day (GD) 12. Litters were examined on GD21. The ED(50) for embryo death with artelinic acid (23.4 µmol/kg) was just slightly lower than that for decreased reticulocyte count at 24 hr postdose (33.5 µmol/kg) and both had similarly steep dose responses (maximal effects of total litter loss and ∼60% decreases in reticulocyte count at 48 µmol/kg). Results with artesunate were similar. The correlation coefficient between embryo death and decreased reticulocyte count was 0.82 (p<0.01). The close relationship between embryotoxicity and reticulocytopenia is suggestive of a common mechanism-artemisinin-induced mitochondrial damage leading to cell death. At 9 days postdose, treatment with artesunate and artelinic acid also caused increases in counts of reticulocytes, lymphocytes, basophils, and monocytes (up to 3.7 ×, 1.7 ×, 4.7 ×, and 1.7 × control, respectively). This stimulation of hematopoiesis may have been mediated by the direct oxidative conversion of artesunate or artelinic acid to the artemisininyl hydroperoxide within the bone marrow cells or by an indirect increase in reactive oxygen species. The high correlation between embryotoxicity and reticulocytopenia further supports the assertion that therapeutic dosage regimens of artemisinins that cause decreases in reticulocyte count in pregnant women during the putative critical period (approximately postconception wk 3 to 9) are at risk of also causing adverse effects on the embryo.

Effects of artemisinin in broiler chickens following chronic oral intake

Artemisinin has been used for centuries to treat malaria, intestinal tract helminthosis, diarrhea, and used as an antipyretic and sedative agent, but the usage in veterinary medicine is a new field. Recently, it has been used successfully to control experimental poultry coccidiosis. The present study aimed to determine the effects of different doses of artemisinin in broiler chickens with chronic usage. Sixty birds divided into one control and four treatment groups that fed rations mixed with artemisinin at doses of 17, 34, 68, and 136 ppm for 36 days. During the experiment, birds showed no clinical signs except anemia. In microscopic examinations, heart, lung, and spleen had no lesion, but liver, kidney, and brain showed various lesions. Degenerative lesions like intracytoplasmic eosinophilic inclusions were seen in both kidney and liver but fatty change was seen only in liver. There was no relationship between severity of the liver lesions and drug dosage. Central chromatolysis, scattered neuronal necrosis, and mild spongy changes were observed in five regions of the brain that were chosen for sectioning (motor cortex, cerebellar nuclei, midbrain nuclei, and hindbrain nuclei at two separate levels). Severity of lesions in brain was dose-dependent, and cerebral cortex was the most vulnerable area. Haematologic tests showed lower values for hematocrit and red blood cell count dose-dependently. In conclusion, artemisinin is a promising drug for prevention and control of coccidiosis in broiler chickens and its side effects are not too much serious especially at therapeutic doses.

WITHDRAWN. Neurological assessments after treatment with the antimalarial β-arteether in neonatal and adult rats

The World Health Organization currently recommends combinatorial treatment including artemisinins as first-line therapy against drug-resistant Plasmodium falciparum malaria. Although highly efficacious, artemisinin and its derivatives, including β-arteether (βAE), are associated with ototoxicity, tremors, and other autonomic and motor impairments in the clinic. Similar neurological symptoms, as well as brainstem lesions, have been observed in adult laboratory species (mice, rats, dogs, and non human primates) following acute treatment with βAE; however, few long-term, nonclinical studies have been conducted. Furthermore, the majority of deaths attributed to malarial infection occur in children under age five, yet no laboratory studies have been initiated in neonatal or juvenile animals. In the current study, neonatal 7-day-old rats were administered intramuscular doses of 1-90mg/kg βAE in sesame oil for up to eight treatment cycles (one cycle=7days treatment+7days without treatment). Neonates were tested for changes in sensorimotor function, and the same animals were tested as adults in the Functional Observational Battery, for motor activity, and in the 8-arm radial maze. Pups receiving a single cycle of 60 or 90mg/kg died within a week of treatment but had few behavioral changes and no brainstem pathology. In the long-term study, behavioral and motor changes and brainstem lesions were observed in a dose- and time-related manner. Rats given repeated cycles of 1 or 5mg/kg βAE showed subtle motor abnormalities (e.g., slight loss of righting reflex) while repeated cycles of 10mg/kg βAE treatment resulted in obvious motor and behavioral changes. Rats receiving 1mg/kg βAE had no brainstem lesions whereas some rats treated with 5mg/kg βAE and all rats treated with 10mg/kg βAE had brainstem lesions. Brainstem lesions were observed after as few as five cycles and were characterized by gliosis, satellitosis and progressive necrosis in motor neurons of the trapezoid, vestibular, and olivary nuclei. This study shows that repeated treatment with clinically relevant doses of βAE causes motor deficits associated with brainstem damage in rodents and suggests that repeated treatment with βAE in children may elicit neurological damage.