Comparative pharmacokinetic study of oral and rectal formulations of artesunic acid in healthy volunteers

Phase I study on the pharmacokinetics of intravaginal, self-administered artesunate vaginal pessaries among women in Kenya

Cervical cancer remains a significant global health issue, especially in low- and middle-income countries (LMICs), where access to prevention and treatment is limited and women are at a higher risk of cervical cancer. Artesunate, a widely available drug used to treat malaria, has shown promise in treating human papillomavirus (HPV)-associated anogenital lesions including high-grade cervical precancer, in a recent Phase I studies in the United States. Data on the pharmacokinetics of artesunate following intravaginal use, and its implications on malaria resistance, are lacking.

Objectives

The primary objective of this study is to investigate the pharmacokinetics of Artesunate (AS) and its active metabolite, dihydroartemisinin (DHA) following intravaginal use at the dosing and frequency intended for cervical precancer treatment. A secondary objective is to assess safety among study participants.

Methods

We are conducting a single-arm, phase I trial with a sample size of 12 female volunteers. Participants will self-administer artesunate vaginal pessaries in the study clinic daily for 5 consecutive days. Participants will have their blood drawn prior to receiving the first dose of artesunate on day one of the study and then will receive 8 blood draws on study day five, prior to artesunate administration and at 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 6 hours, and 8 hours after pessary administration. Pharmacokinetic parameters of artesunate and DHA will be calculated by way of quantitative analysis of with determination of maximum concentration (Cmax), time to Cmax (Tmax), area under the plasma concentration versus time curve (AUC), apparent clearance, and elimination half-life (t1/2).

Artesunate: A review of its therapeutic insights in respiratory diseases

BACKGROUND

Artesunate, as a semi-synthetic artemisinin derivative of sesquiterpene lactone, is widely used in clinical antimalarial treatment due to its endoperoxide group. Recent studies have found that artesunate may have multiple pharmacological effects, indicating its significant therapeutic potential in multiple respiratory diseases.

PURPOSE

This review aims to summarize proven and potential therapeutic effects of artesunate in common respiratory disorders.

STUDY DESIGN

This review summarizes the pharmacological properties of artesunate and then interprets the function of artesunate in various respiratory diseases in detail, such as bronchial asthma, chronic obstructive pulmonary disease, lung injury, lung cancer, pulmonary fibrosis, coronavirus disease 2019, etc., on different target cells and receptors according to completed and ongoing in silico, in vitro, and in vivo studies (including clinical trials).

METHODS

Literature was searched in electronic databases, including Pubmed, Web of Science and CNKI with the primary keywords of 'artesunate', 'pharmacology', 'pharmacokinetics', 'respiratory disorders', 'lung', 'pulmonary', and secondary search terms of 'Artemisia annua L.', 'artemisinin', 'asthma', 'chronic obstructive lung disease', 'lung injury', 'lung cancer', 'pulmonary fibrosis', 'COVID-19' and 'virus' in English and Chinese. All experiments were included. Reviews and irrelevant studies to the therapeutic effects of artesunate on respiratory diseases were excluded. Information was sort out according to study design, subject, intervention, and outcome.

RESULTS

Artesunate is promising to treat multiple common respiratory disorders via various mechanisms, such as anti-inflammation, anti-oxidative stress, anti-hyperresponsiveness, anti-proliferation, airway remodeling reverse, induction of cell death, cell cycle arrest, etc. CONCLUSION: Artesunate has great potential to treat various respiratory diseases.

Bioactive Compounds, Pharmacological Actions, and Pharmacokinetics of Wormwood (Artemisia absinthium)

Plants have been used since ancient times to cure certain infectious diseases, and some of them are now standard treatments for several diseases. Due to the side effects and resistance of pathogenic microorganisms to antibiotics and most drugs on the market, a great deal of attention has been paid to extracts and biologically active compounds isolated from plant species used in herbal medicine. Artemisia absinthium is an important perennial shrubby plant that has been widely used for the treatment of several ailments. Traditionally, A. absinthium has always been of pharmaceutical and botanical importance and used to manage several disorders including hepatocyte enlargement, hepatitis, gastritis, jaundice, wound healing, splenomegaly, dyspepsia, indigestion, flatulence, gastric pain, anemia, and anorexia. It has also been documented to possess antioxidant, antifungal, antimicrobial, anthelmintic, anti-ulcer, anticarcinogenic, hepatoprotective, neuroprotective, antidepressant, analgesic, immunomodulatory, and cytotoxic activity. Long-term use of A. absinthium essential oil may cause toxic and mental disorders in humans with clinical manifestations including convulsions, sleeplessness, and hallucinations. Combination chemotherapies of artemisia extract or its isolated active constituents with the currently available antibabesial or anti-malarial drugs are now documented to relieve malaria and piroplasmosis infections. The current review examines the phytoconstituents, toxic and biological activities of A. absinthium.

An evaluation of rectal artesunate for the pre-hospital management of severe malaria

INTRODUCTION

Severe falciparum malaria stills accounts for around half a million childhood deaths per year in sub-Saharan Africa. Prompt treatment of sick children close to home starting with artesunate given rectally by appropriately trained people can be lifesaving.

AREAS COVERED

Rectal artesunate (RAS) has been developed for use in the WHO approved strategy of pre-referral intervention. This review covers the formulation, pharmacokinetics, safety, efficacy, and implementation of this drug. There is little RCT evidence and the only RCT has been controversial. It is unlikely that there will be further randomized studies in the field. There is a concern that the administration of a single dose of artesunate without adequate follow up therapy may encourage the emergence of artemisinin resistance.

EXPERT OPINION

Artesunate is an essential drug and RAS is a very useful, potentially lifesaving formulation designed to be quickly administered in remote areas to severely unwell children by non-medical personnel. However, its use needs to be monitored and onward referral for definitive antimalarial treatment ensured.

Systematic review of artesunate pharmacokinetics: Implication for treatment of resistant malaria

BACKGROUND

Artesunate (ART) is an artemisinin derivative used as monotherapy for the treatment of severe malaria and in combination with a partner drug for non-severe malaria. Resistance of malaria parasites to artemisinins have emerged in Southeast Asia. Adjustment of drug regimen may be an option to prevent therapeutic failures considering the relative favourable safety profile of ART high doses.

METHODS

For that purpose, a systematic review was done using PubMed, Scopus and Web of Science databases. All studies on ART and DHA pharmacokinetic post-administration of artesunate in human patients or volunteers were included. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist 2009 was used.

FINDINGS

Fifty studies exploring oral, intravenous, rectal, and intramuscular route (1470 persons, volunteers and patients) were included. Correlations between artesunate doses and C_max or AUC_0-∞ of dihydroartemisinin (DHA) and DHA+ART were evaluated. This correlation was good (R²>0.9) using intravenous (IV) route. DHA and ART+DHA average concentrations (Cav) were well above estimated in vivo half-maximal effective concentration (EC₅₀) for intravenous route, but this was not the case for oral route.

INTERPRETATION

The favorable Cav/EC₅₀ ratio for IV route provides evidence that IV ART will remain efficient even in the case of increased resistance level, whereas for the oral route, a two-fold increase in EC₅₀ may lead to therapeutic failures, thus providing a rationale for oral dose escalation. Considering the inter-individual variability of ART pharmacokinetic, Therapeutic Drug Monitoring through antimalarial stewardship activities is needed to optimize drug exposure and avoid resistance development.

Effects of artesunate against Trypanosma cruzi

Therapy against Trypanosma cruzi relies on only two chemically related nitro-derivative drugs, benznidazole and nifurtimox, both limited by poor efficacy and toxicity. It is suspected that with prolonged usage of these drugs, resistant parasites will be selected, which results in risk for treatment failure over the time. Herein, we studied the in vitro activity of artesunate, the most effective drug to treat severe P. falciparum and chloroquine-resistant P. vivax, on three strains of T. cruzi originated in different regions of Latin America (Argentina, Nicaragua and Brazil). The results of these assays showed that artesunate inhibits multiplication of epimastigotes (IC50 = 50, 6.10 and 23 µM, respectively) and intracellular amastigotes (IC50 = 15, 0.12 and 6.90 µM, respectively), indicating that it represents a potent anti-T. cruzi compound in terms of inhibiting parasite multiplication in vitro. We then tested the effect of artesunate in Balb/c mice infected with Brazil strain and found that it failed to cure the infection, suggesting that the drug may be unsuitable for in vivo treatment. When infected mice were treated with high doses AS + BZ, the outcome of infection was similar to that observed in mice treated with BZ alone. Nevertheless, understanding of structure-activity relationship of artesunate might lead to the development of new and effective drugs against T. cruzi.

Review of the clinical pharmacokinetics of artesunate and its active metabolite dihydroartemisinin following intravenous, intramuscular, oral or rectal administration

Artesunate (AS) is a clinically versatile artemisinin derivative utilized for the treatment of mild to severe malaria infection. Given the therapeutic significance of AS and the necessity of appropriate AS dosing, substantial research has been performed investigating the pharmacokinetics of AS and its active metabolite dihydroartemisinin (DHA). In this article, a comprehensive review is presented of AS clinical pharmacokinetics following administration of AS by the intravenous (IV), intramuscular (IM), oral or rectal routes. Intravenous AS is associated with high initial AS concentrations which subsequently decline rapidly, with typical AS half-life estimates of less than 15 minutes. AS clearance and volume estimates average 2 - 3 L/kg/hr and 0.1 - 0.3 L/kg, respectively. DHA concentrations peak within 25 minutes post-dose, and DHA is eliminated with a half-life of 30 - 60 minutes. DHA clearance and volume average between 0.5 - 1.5 L/kg/hr and 0.5 - 1.0 L/kg, respectively. Compared to IV administration, IM administration produces lower peaks, longer half-life values, and higher volumes of distribution for AS, as well as delayed peaks for DHA; other parameters are generally similar due to the high bioavailability, assessed by exposure to DHA, associated with IM AS administration (> 86%). Similarly high bioavailability of DHA (> 80%) is associated with oral administration. Following oral AS, peak AS concentrations (Cmax) are achieved within one hour, and AS is eliminated with a half-life of 20 - 45 minutes. DHA Cmax values are observed within two hours post-dose; DHA half-life values average 0.5 - 1.5 hours. AUC values reported for AS are often substantially lower than those reported for DHA following oral AS administration. Rectal AS administration yields pharmacokinetic results similar to those obtained from oral administration, with the exceptions of delayed AS Cmax and longer AS half-life. Drug interaction studies conducted with oral AS suggest that AS does not appreciably alter the pharmacokinetics of atovaquone/proguanil, chlorproguanil/dapsone, or sulphadoxine/pyrimethamine, and mefloquine and pyronaridine do not alter the pharmacokinetics of DHA. Finally, there is evidence suggesting that the pharmacokinetics of AS and/or DHA following AS administration may be altered by pregnancy and by acute malaria infection, but further investigation would be required to define those alterations precisely.

Population pharmacokinetics of artesunate and dihydroartemisinin following single- and multiple-dosing of oral artesunate in healthy subjects

Background

The population pharmacokinetics of artesunate (AS) and its active metabolite dihydroartemisinin (DHA) were studied in healthy subjects receiving single- or multiple-dosing of AS orally either in combination with pyronaridine (PYR) or as a monotherapy with or without food.

Methods

Data from 118 concentration-time profiles arising from 91 healthy Korean subjects were pooled from four Phase I clinical studies. Subjects received 2-5 mg/kg of single- and multiple-dosing of oral AS either in combination with PYR or as a monotherapy with or without food. Plasma AS and DHA were measured simultaneously using a validated liquid chromatography- mass spectrometric method with a lower limit of quantification of 1 ng/mL for both AS and DHA. Nonlinear mixed-effect modelling was used to obtain the pharmacokinetic and variability (inter-individual and residual variability) parameter estimates.

Results

A novel parent-metabolite pharmacokinetic model consisting of a dosing compartment, a central compartment for AS, a central compartment and a peripheral compartment for DHA was developed. AS and DHA data were modelled simultaneously assuming stoichiometric conversion to DHA. AS was rapidly absorbed with a population estimate of absorption rate constant (Ka) of 3.85 h^-1. The population estimates of apparent clearance (CL/F) and volume of distribution (V2/F) for AS were 1190 L/h with 36.2% inter-individual variability (IIV) and 1210 L with 57.4% IIV, respectively. For DHA, the population estimates of apparent clearance (CLM/F) and central volume of distribution (V3/F) were 93.7 L/h with 28% IIV and 97.1 L with 30% IIV, respectively. The population estimates of apparent inter-compartmental clearance (Q/F) and peripheral volume of distribution (V4/F) for DHA were 5.74 L/h and 18.5 L, respectively. Intake of high-fat and high-caloric meal prior to the drug administration resulted in 84% reduction in Ka. Body weight impacted CLM/F, such that a unit change in weight resulted in 1.9-unit change in CLM/F in the same direction.

Conclusions

A novel simultaneous parent-metabolite pharmacokinetic model with good predictive power was developed to study the population pharmacokinetics of AS and DHA in healthy subjects following single- and multiple-dosing of AS with or without the presence of food. Food intake and weight were significant covariates for Ka and CLM/F, respectively.

Tolerability and pharmacokinetics of non-fixed and fixed combinations of artesunate and amodiaquine in Malaysian healthy normal volunteers

Objective

There is limited pharmacokinetic data available for the combination artesunate + amodiaquine, which is used widely to treat uncomplicated malaria. This study examines the bioavailability and tolerability of a fixed (200 mg artesunate + 540 mg amodiaquine) and loose (200 mg + 612 mg) combination with a 2×2 cross-over design in 24 healthy volunteers.

Methods

Parent compounds and metabolites [dihydroartemisinin (DHA) and desethylamodiaquine (DEAQ)] were measured by high-performance liquid chromatography–electrochemical detection, and the area under the curve (AUC)_0-t and C_max were compared by an analysis of variance (ANOVA) based on geometric least square means using the Schuirmann two one-sided test.

Results

The AUC_0-t for total DHA and DEAQ were 1522 ± 633 and 30021 ± 14211 ng h/ml for the fixed products and 1688 ± 767 and 40261 ± 19824 ng h/ml (mean ± standard deviation) for the loose products. The ANOVA showed no statistical differences except for sequence effect for DHA. The values obtained with the fixed product were within the 125% bioequivalent limits but extend below the 80% bioequivalence limits.

Conclusion

Both combinations were well tolerated and had comparable pharmacokinetic profiles; differences are unlikely to be clinically relevant.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-009-0656-1) contains supplementary material, which is available to authorized users.

Geometric least squares means ratios for the analysis of Plasmodium falciparum in vitro susceptibility to antimalarial drugs

Background

The susceptibility of microbes such as Plasmodium falciparum to drugs is measured in vitro as the concentration of the drug achieving 50% of maximum effect (IC₅₀); values from a population are summarized as geometric means. For antimalarial drugs, as well as for antibiotics, assessing changes in microbe susceptibility over time under drug pressure would help inform treatment policy decisions, but no standard statistical method exists as yet.

Methods

A mixed model was generated on log_e-transformed IC₅₀ values and calculated geometric least squares means (GLSM) with 90% confidence intervals (CIs). In order to compare IC₅₀s between years, GLSM ratios (GLSMR) with 90%CIs were calculated and, when both limits of the 90%CIs were below or above 100%, the difference was considered statistically significant. Results were compared to those obtained from ANOVA and a generalized linear model (GLM).

Results

GLSMRs were more conservative than ANOVA and resulted in lower levels of statistical significance. The GLSMRs approach allowed for random effect and adjustment for multiple comparisons. GLM was limited in the number of year-to-year comparisons by the need for a single reference year. The three analyses yielded generally consistent results.

Conclusion

A robust analytical method can palliate inherent limitations of in vitro sensitivity testing. The random effects GLSMRs with adjustment for multiple comparisons and 90%CIs require only assumptions on the mixed model to be applied. Results are easy to display graphically and to interpret. The GLMSRs should be considered as an option for monitoring changes in drug susceptibility of P. falciparum malaria and other microbes.

Artemisinins

Artemisinins were discovered to be highly effective antimalarial drugs shortly after the isolation of the parent artemisinin in 1971 in China. These compounds combine potent, rapid antimalarial activity with a wide therapeutic index and an absence of clinically important resistance. Artemisinin containing regimens meet the urgent need to find effective treatments for multidrug resistant malaria and have recently been advocated for widespread deployment. Comparative trials of artesunate and quinine for severe malaria are in progress to see if the persistently high mortality of this condition can be reduced.

Randomised efficacy and safety study of two 3-day artesunate rectal capsule/mefloquine regimens versus artesunate alone for uncomplicated malaria in Ecuadorian children

The combination of artesunate and mefloquine is one of the most effective treatments against multidrug-resistant falciparum malaria. Experience in children is however limited. The objective of this study was to compare the efficacy and safety of two artesunate/mefloquine combinations with artesunate monotherapy in Ecuadorian children. A total of 150 children with an age between 2 and 12 years, confirmed to have uncomplicated falciparum malaria, were randomly selected and divided in three treatment groups of 50 patients each. Group 1 received 50 mg rectal capsules alone (40 mg/kg total dose) administered over 6 days. Group 2 received 50 mg rectal capsules (30 mg/kg total dose) for 3 days combined with mefloquine (20 mg/kg total dose) on day 1. Group 3 was treated with 50 mg rectal capsules (30 mg/kg total dose) for 3 days, combined with mefloquine on days 1 and 3 (15-17 mg/kg total dose). Patients were continuously followed up and controlled by clinical and laboratory examinations for 7 days as well as on days 14, 21 and 28. An additional parasite examination was performed at 2 months following therapy. Clearance of parasitaemia was comparable between treatment groups. These were 9.2, 9.2 and 8.3 h for Groups 1, 2 and 3, respectively. Cure rates at day 28 were 76, 96 and 94% and after 2 months 60, 88 and 80%, respectively. There were no adverse events (AEs) reported during the study. Vital signs and laboratory examinations revealed no changes of clinical relevance. It can be concluded that the combination of artesunate rectal capsules with mefloquine is effective and safe. Starting concomitant administration already on day 1 is well tolerated. This combination significantly reduces the incidence of recrudescence compared to artesunate monotherapy. Comparing the two tested artesunate/mefloquine regimens, a total mefloquine dose of 20 mg/kg seems to be more effective compared to a total dose of 15-17 mg/kg. Further studies seem to be warranted.

The pharmacokinetic properties of intramuscular artesunate and rectal dihydroartemisinin in uncomplicated falciparum malaria

AIMS

To obtain pharmacokinetic data for artesunate (ARTS) and its active metabolite dihydroartemisinin (DHA) following i.m. ARTS and rectal DHA administration.

METHODS

Twelve Vietnamese patients with uncomplicated falciparum malaria were randomized to receive either i.v. or i.m. ARTS (120 mg), with the alternative preparation given 8 h later in an open crossover design. A further 12 patients were given i.v. ARTS (120 mg) at 0 h and rectal DHA (160 mg) 8 h later.

RESULTS

Following i.v. bolus, ARTS had a peak concentration of 42 microm (16 mg l(-1), elimination t1/2 = 3.2 min, CL = 2.8 l h(-1) kg(-1) and V = 0.22 l kg(-1) . The Cmax for DHA was 9.7 microm (2.7 mg l(-1) ), t1/2 = 59 min, CL = 0.64 l h(-1) kg(-1) and V = 0.8 l kg(-1) . Following i.m. ARTS, Cmax was 2.3 microm (3.7 mg l(-1)), the apparent t1/2 = 41 min, CL = 2.9 l h(-1) kg(-1) and V = 2.6 l kg(-1). The relative bioavailability of DHA was 88%, Cmax was 4.1 microm (1.16 mg l(-1)) and t1/2 = 64 min. In the rectal DHA study, relative bioavailability of DHA was 16%.

CONCLUSIONS

For patients with uncomplicated falciparum malaria i.m. ARTS is a suitable alternative to i.v. ARTS, at equal doses. To achieve plasma DHA concentrations equivalent to parenteral administration of ARTS, rectal DHA should be given at approximately four-fold higher milligram doses. Further studies are needed to determine whether these recommendations can be applied to patients with severe malaria.

Pharmacokinetics of artemisinin-type compounds

Various compounds of the artemisinin family are currently used for the treatment of patients with malaria worldwide. They are characterised by a short half-life and feature the most rapidly acting antimalarial drugs to date. They are increasingly being used, often in combination with other drugs, although our knowledge of their main pharmacological features (including their absorption, distribution, metabolism and excretion) is still incomplete. Such data are particularly important in the case of combinations. Artemisinin derivatives are converted primarily, but to different extents, to the bioactive metabolite artenimol after either parenteral or gastrointestinal administration. The rate of conversion is lowest for artelinic acid (designed to protect the molecule against metabolism) and highest for the water-soluble artesunate. The absolute and relative bioavailability of these compounds has been established in animals, but not in humans, with the exception of artesunate. Oral bioavailability in animals ranges, approximately, between 19 and 35%. A first-pass effect is highly probably for all compounds when administered orally. Artemisinin compounds bind selectively to malaria-infected erythrocytes to yet unidentified targets. They also bind modestly to human plasma proteins, ranging from 43% for artenimol to 81.5% for artelinic acid. Their mode of action is still not completely understood, although different theories have been proposed. The lipid-soluble artemether and artemotil are released slowly when administered intramuscularly because of the 'depot' effect related to the oil formulation. Understanding the pharmacokinetic profile of these 2 drugs helps us to explain the characteristics of the toxicity and neurotoxicity. The water-soluble artesunate is rapidly converted to artenimol at rates that vary with the route of administration, but the processes need to be characterised further, including the relative contribution of pH and enzymes in tissues, blood and liver. This paper intends to summarise contemporary knowledge of the pharmacokinetics of this class of compounds and highlight areas that need further research.