Translational Modeling of Chloroquine and Hydroxychloroquine Dosimetry in Human Airways for Treating Viral Respiratory Infections

Purpose

Chloroquine and hydroxychloroquine are effective against respiratory viruses in vitro. However, they lack antiviral efficacy upon oral administration. Translation of in vitro to in vivo exposure is necessary for understanding the disconnect between the two to develop effective therapeutic strategies.

Methods

We employed an in vitro ion-trapping kinetic model to predict the changes in the cytosolic and lysosomal concentrations of chloroquine and hydroxychloroquine in cell lines and primary human airway cultures. A physiologically based pharmacokinetic model with detailed respiratory physiology was used to predict regional airway exposure and optimize dosing regimens.

Results

At their reported in vitro effective concentrations in cell lines, chloroquine and hydroxychloroquine cause a significant increase in their cytosolic and lysosomal concentrations by altering the lysosomal pH. Higher concentrations of the compounds are required to achieve similar levels of cytosolic and lysosomal changes in primary human airway cells in vitro. The predicted cellular and lysosomal concentrations in the respiratory tract for in vivo oral doses are lower than the in vitro effective levels. Pulmonary administration of aerosolized chloroquine or hydroxychloroquine is predicted to achieve high bound in vitro-effective concentrations in the respiratory tract, with low systemic exposure. Achieving effective cytosolic concentrations for activating immunomodulatory effects and adequate lysosomal levels for inhibiting viral replication could be key drivers for treating viral respiratory infections.

Conclusion

Our analysis provides a framework for extrapolating in vitro effective concentrations of chloroquine and hydroxychloroquine to in vivo dosing regimens for treating viral respiratory infections.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-021-03152-3.

HPLC methods for choloroquine determination in biological samples and pharmaceutical products

OBJECTIVE

Review and assess pharmaceutical and clinical characteristics of chloroquine including high-performance liquid chromatography (HPLC)-based methods used to quantify the drug in pharmaceutical products and biological samples.

EVIDENCE ACQUISITION

A literature review was undertaken on the PubMed, Science Direct, and Scielo databases using the following keywords related to the investigated subject: 'chloroquine', 'analytical methods', and 'HPLC'.

RESULTS

For more than seven decades, chloroquine has been used to treat malaria and some autoimmune diseases, such as lupus erythematosus and rheumatoid arthritis. There is growing interest in chloroquine as a therapeutic alternative in the treatment of HIV, Q fever, Whipple's disease, fungal, Zika, Chikungunya infections, Sjogren's syndrome, porphyria, chronic ulcerative stomatitis, polymorphic light eruption, and different types of cancer. HPLC coupled to UV detectors is the most employed method to quantify chloroquine in pharmaceutical products and biological samples. The main chromatographic conditions used to identify and quantify chloroquine from tablets and injections, degradation products, and metabolites are presented and discussed.

CONCLUSION

Research findings reported in this article may facilitate the repositioning, quality control, and biological monitoring of chloroquine in modern pharmaceutical dosage forms and treatments.

Population-based meta-analysis of chloroquine: informing chloroquine pharmacokinetics in COVID-19 patients

AIMS

Chloroquine (CQ) has been repurposed to treat coronavirus disease 2019 (COVID-19). Understanding the pharmacokinetics (PK) in COVID-19 patients is essential to study its exposure-efficacy/safety relationship and provide a basis for a possible dosing regimen optimization.

SUBJECT AND METHODS

In this study, we used a population-based meta-analysis approach to develop a population PK model to characterize the CQ PK in COVID-19 patients. An open-label, single-center study (ethical review approval number: PJ-NBEY-KY-2020-063-01) was conducted to assess the safety, efficacy, and pharmacokinetics of CQ in patients with COVID-19. The sparse PK data from 50 COVID-19 patients, receiving 500 mg CQ phosphate twice daily for 7 days, were combined with additional CQ PK data from 18 publications.

RESULTS

A two-compartment model with first-order oral absorption and first-order elimination and an absorption lag best described the data. Absorption rate (ka) was estimated to be 0.559 h-1, and a lag time of absorption (ALAG) was estimated to be 0.149 h. Apparent clearance (CL/F) and apparent central volume of distribution (V2/F) was 33.3 l/h and 3630 l. Apparent distribution clearance (Q/F) and volume of distribution of peripheral compartment (Q3/F) were 58.7 l/h and 5120 l. The simulated CQ concentration under five dosing regimens of CQ phosphate were within the safety margin (400 ng/ml).

CONCLUSION

Model-based simulation using PK parameters from the COVID-19 patients shows that the concentrations under the currently recommended dosing regimen are below the safety margin for side-effects, which suggests that these dosing regimens are generally safe. The derived population PK model should allow for the assessment of pharmacokinetics-pharmacodynamics (PK-PD) relationships for CQ when given alone or in combination with other agents to treat COVID-19.

COVID-19 prevention and treatment: A critical analysis of chloroquine and hydroxychloroquine clinical pharmacology

Nicholas White and coauthors discuss chloroquine and hydroxychloroquine pharmacology in the context of possible treatment of SARS-CoV-2 infection.

Chloroquine Dosing Recommendations for Pediatric COVID-19 Supported by Modeling and Simulation

As chloroquine (CHQ) is part of the Dutch Centre for Infectious Disease Control coronavirus disease 2019 (COVID-19) experimental treatment guideline, pediatric dosing guidelines are needed. Recent pediatric data suggest that existing World Health Organization (WHO) dosing guidelines for children with malaria are suboptimal. The aim of our study was to establish best-evidence to inform pediatric CHQ doses for children infected with COVID-19. A previously developed physiologically-based pharmacokinetic (PBPK) model for CHQ was used to simulate exposure in adults and children and verified against published pharmacokinetic data. The COVID-19 recommended adult dosage regimen of 44 mg/kg total was tested in adults and children to evaluate the extent of variation in exposure. Based on differences in area under the concentration-time curve from zero to 70 hours (AUC0-70h ) the optimal CHQ dose was determined in children of different ages compared with adults. Revised doses were re-introduced into the model to verify that overall CHQ exposure in each age band was within 5% of the predicted adult value. Simulations showed differences in drug exposure in children of different ages and adults when the same body-weight based dose is given. As such, we propose the following total cumulative doses: 35 mg/kg (CHQ base) for children 0-1 month, 47 mg/kg for 1-6 months, 55 mg/kg for 6 months-12 years, and 44 mg/kg for adolescents and adults, not to exceed 3,300 mg in any patient. Our study supports age-adjusted CHQ dosing in children with COVID-19 in order to avoid suboptimal or toxic doses. The knowledge-driven, model-informed dose selection paradigm can serve as a science-based alternative to recommend pediatric dosing when pediatric clinical trial data is absent.

Building on Surface-Active Ionic Liquids for the Rescuing of the Antimalarial Drug Chloroquine

Ionic liquids derived from classical antimalarials are emerging as a new approach towards the cost-effective rescuing of those drugs. Herein, we disclose novel surface-active ionic liquids derived from chloroquine and natural fatty acids whose antimalarial activity in vitro was found to be superior to that of the parent drug. The most potent ionic liquid was the laurate salt of chloroquine, which presented IC₅₀ values of 4 and 110 nM against a chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium falciparum, respectively, corresponding to an 11- and 6-fold increase in potency as compared to the reference chloroquine bisphosphate salt against the same strains. This unprecedented report opens new perspectives in both the fields of malaria chemotherapy and of surface-active ionic liquids derived from active pharmaceutical ingredients.

Primum non nocere - Are chloroquine and hydroxychloroquine safe prophylactic/treatment options for SARS-CoV-2 (covid-19)?

Chloroquine (CQ) and its analog hydroxychloroquine (HCQ) were recently included in several clinical trials as potential prophylactic and therapeutic options for SARS-COV-2 infection/covid-19. However, drug effectiveness in preventing, treating, or slowing the progression of the disease is still unknown. Despite some initial promising in vitro results, rigorous pre-clinical animal studies and randomized clinical trials have not been performed yet. On the other hand, while the potential effectiveness of CQ/HCQ is, at best, hypothetical, their side effects are factual and most worrisome, particularly when considering vulnerable groups of patients being treated with these drugs. in this comment, we briefly explain the possible mechanisms of action of CQ/HCQ for treating other diseases, possible actions against covid-19, and their potent side effects, in order to reinforce the necessity of evaluating the benefit-risk balance when widely prescribing these drugs for SARS-COV-2 infection/covid-19. We conclude by strongly recommending against their indiscriminate use.

Insights from nanomedicine into chloroquine efficacy against COVID-19

Chloroquine — an approved malaria drug — is known in nanomedicine research for the investigation of nanoparticle uptake in cells, and may have potential for the treatment of COVID-19.

Cardiac safety of off-label COVID-19 drug therapy: a review and proposed monitoring protocol

More than 2,000,000 individuals worldwide have had coronavirus 2019 disease infection (COVID-19), yet there is no effective medical therapy. Multiple off-label and investigational drugs, such as chloroquine and hydroxychloroquine, have gained broad interest due to positive pre-clinical data and are currently used for treatment of COVID-19. However, some of these medications have potential cardiac adverse effects. This is important because up to one-third of patients with COVID-19 have cardiac injury, which can further increase the risk of cardiomyopathy and arrhythmias. Adverse effects of chloroquine and hydroxychloroquine on cardiac function and conduction are broad and can be fatal. Both drugs have an anti-arrhythmic property and are proarrhythmic. The American Heart Association has listed chloroquine and hydroxychloroquine as agents which can cause direct myocardial toxicity. Similarly, other investigational drugs such as favipiravir and lopinavir/ritonavir can prolong QT interval and cause Torsade de Pointes. Many antibiotics commonly used for the treatment of patients with COVID-19, for instance azithromycin, can also prolong QT interval. This review summarizes evidenced-based data regarding potential cardiac adverse effects due to off-label and investigational drugs including chloroquine and hydroxychloroquine, antiviral therapy, monoclonal antibodies, as well as common antibiotics used for the treatment of COVID-19. The article focuses on practical points and offers a point-of-care protocol for providers who are taking care of patients with COVID-19 in an inpatient and outpatient setting. The proposed protocol is taking into consideration that resources during the pandemic are limited.

Co-delivery nanoparticles of doxorubicin and chloroquine for improving the anti-cancer effect in vitro

To increase the efficacy of small molecule chemotherapeutic drug (SMCD) and reduce its toxic and side effects, we selected two model drugs doxorubicin (DOX) and chloroquine (CQ). DOX is a SMCD and CQis a chemosensitizer with autophagy inhibition. Poly(lactic-co-glycolic acid) (PLGA) and alpha-tocopherol polyethylene glycol 1000 succinate were chosen as delivery carriers to design and prepare a novel type of drug co-delivery single-nanoparticles by emulsification-solvent volatilisation, named NP_DOX+CQ. The physicochemical properties of NP_DOX+CQ were characterised. Then A549 cells and A549/Taxol cells were used for the in vitro anti-cancer effect study. At the same time, cellular uptake, intracellular migration and anti-cancer mechanism of nanoparticles were studied. The NPs showed a uniform spherical shape with good dispersibility, and both drugs had good encapsulation efficiency and loading capacity. In all formulations, NP_DOX+CQ showed the highest in vitro cytotoxicity. The results showed that NPs could protect drugs from being recognised and excluded by P-glycoprotein (P-gp). Moreover, the results of the mechanistic study demonstrated that NPs were transported by autophagy process after being taken up by the cells. Therefore, during the migration of NP_DOX+CQ, CQ could exert its efficacy and block autophagy so that DOX would not be hit by autophagy. Western Blot results showed that NP_DOX+CQ had the best inhibition effect of autophagy. It can be concluded that the system can prevent the drug from being recognised and excluded by P-gp, and CQ blocks the process of autophagy so that the DOX is protected and more distributed to the nucleus of multidrug resistance (MDR) cell. The NP_DOX+CQ constructed in this study provides a feasible strategy for reversing MDR in tumour cells.

Supramolecular self-assembly of triazine-based small molecules: targeting the endoplasmic reticulum in cancer cells

The endoplasmic reticulum (ER) is one of the most important organelles controlling myriads of cellular functions including protein folding/misfolding/unfolding, calcium ion homeostasis and lipid biosynthesis. Subsequently, due to its functional dysregulation in cancer cells, it has emerged as an interesting target for anti-cancer therapy. However, specific targeting of the ER in cancer cells remains a major challenge due to the lack of ER-selective chemical tools. Furthermore, for performing multiple cellular functions the ER is dependent on the nucleus through complicated cross-talk. Herein, we have engineered a supramolecular self-assembled hexameric rosette structure from two small molecules: tri-substituted triazine and 5-fluorouracil (5-FU). This rosette structure consists of an ER-targeting moiety with a fluorescence tag, an ER-stress inducer and a nuclear DNA damaging drug simultaneously, which further self-assembled into an ER-targeting spherical nano-scale particle (ER-NP). These ER-NPs internalized into HeLa cervical cancer cells by macropinocytosis and specifically localized into the ER to induce ER stress and DNA damage leading to cell death through apoptosis. Interestingly, ER-NPs initiated autophagy, inhibited by a combination of ER-NPs and chloroquine (CQ) to augment cancer cell death. This work has the potential to exploit the concept of supramolecular self-assembly into developing novel nano-scale materials for specific sub-cellular targeting of multiple organelles for future anti-cancer therapy.

Pharmacokinetics and efficacy of orally administered polymeric chloroquine as macromolecular drug in the treatment of inflammatory bowel disease

Inflammatory bowel disease is a chronic inflammation of the gastrointestinal tract with poor understanding of its pathogenesis and no effective cure. The goal of this study was to evaluate the feasibility of orally administered non-degradable polymeric chloroquine (pCQ) to locally reduce colon inflammation. The pCQ was synthesized by radical copolymerization of N-(2-hydroxypropyl)methacrylamide with methacryloylated hydroxychloroquine (HCQ). The anti-inflammatory activity of orally administered pCQ versus HCQ was tested in a mouse model of colitis induced by Citrobacter rodentium (C. rodentium). Single-dose pharmacokinetic and biodistribution studies performed in the colitis model indicated negligible systemic absorption (p ≤ 0.001) and localization of pCQ in the gastrointestinal tract. A multi-dose therapeutic study demonstrated that the localized pCQ treatment resulted in significant reduction in the colon inflammation (p ≤ 0.05). Enhanced suppression of pro-inflammatory cytokines IL-6 (p ≤ 0.01) and IL1-β and opposing upregulation of IL-2 (p ≤ 0.05) recently reported to be involved in downstream anti-inflammatory events suggested that the anti-inflammatory effects of the pCQ are mediated by altering mucosal immune homeostasis. Overall, the reported findings demonstrate a potential of pCQ as a novel polymer therapeutic option in inflammatory bowel disease with the potential of local effects and minimized systemic toxicity.

Effect of Antiretroviral Therapy on Plasma Concentrations of Chloroquine and Desethyl-chloroquine

The effect of antiretroviral therapy (ART) on chloroquine and desethyl-chloroquine plasma concentrations was evaluated in clinical trial participants. Concentrations did not differ among participants receiving protease inhibitor-based ART (n = 9), efavirenz-based ART (n = 15), or other ART (n = 8) and those not receiving ART (n = 31). Efavirenz seemed to inhibit chloroquine desethylation.

Study protocol of a phase IB/II clinical trial of metformin and chloroquine in patients with IDH1-mutated or IDH2-mutated solid tumours

INTRODUCTION

High-grade chondrosarcoma, high-grade glioma and intrahepatic cholangiocarcinoma are aggressive types of cancer with a dismal outcome. This is due to the lack of effective treatment options, emphasising the need for novel therapies. Mutations in the genes IDH1 and IDH2 (isocitrate dehydrogenase 1 and 2) occur in 60% of chondrosarcoma, 80% of WHO grade II-IV glioma and 20% of intrahepatic cholangiocarcinoma. IDH1/2-mutated cancer cells produce the oncometabolite D-2-hydroxyglutarate (D-2HG) and are metabolically vulnerable to treatment with the oral antidiabetic metformin and the oral antimalarial drug chloroquine.

METHODS AND ANALYSIS

We describe a dose-finding phase Ib/II clinical trial, in which patients with IDH1/2-mutated chondrosarcoma, glioma and intrahepatic cholangiocarcinoma are treated with a combination of metformin and chloroquine. Dose escalation is performed according to a 3+3 dose-escalation scheme. The primary objective is to determine the maximum tolerated dose to establish the recommended dose for a phase II clinical trial. Secondary objectives of the study include (1) determination of pharmacokinetics and toxic effects of the study therapy, for which metformin and chloroquine serum levels will be determined over time; (2) investigation of tumour responses to metformin plus chloroquine in IDH1/2-mutated cancers using CT/MRI scans; and (3) whether tumour responses can be measured by non-invasive D-2HG measurements (mass spectrometry and magnetic resonance spectroscopy) of tumour tissue, serum, urine, and/or bile or next-generation sequencing of circulating tumour DNA (liquid biopsies). This study may open a novel treatment avenue for IDH1/2-mutated high-grade chondrosarcoma, glioma and intrahepatic cholangiocarcinoma by repurposing the combination of two inexpensive drugs that are already approved for other indications.

ETHICS AND DISSEMINATION

This study has been approved by the medical-ethical review committee of the Academic Medical Center, Amsterdam, The Netherlands. The report will be submitted to a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

This article was registered at ClinicalTrials.gov identifier (NCT02496741): Pre-results.

Evaluation of the paediatric dose of chloroquine in the treatment of Plasmodium vivax malaria

BACKGROUND

Chloroquine (CQ) continues to be the first-line medication used worldwide in the treatment of Plasmodium vivax malaria. The dose recommended by the World Health Organization is 25 mg/kg independently of the age of the subject. Nonetheless, the pharmacokinetics and pharmacodynamics of drugs in children are different from those in adults and may influence the drug concentrations in blood and become risk factors for therapeutic failure and/o resistance to CQ.

METHODS

This study is a secondary analysis of the data from a clinical trial in which children over 5 years of age were administered 25 mg/kg of CQ, and CQ concentrations in blood were measured at day 7 of follow-up. Models of regression and comparison were used to evaluate and compare the CQ dose taken per kg/body weight, the CQ dose calculated based on body surface area, CQ levels in blood on day 7 and the age of the population.

RESULTS

The younger the study population the greater the difference between the dose per kg/body weight (real dose) and that calculated according to the BSA (theoretical dose). The difference between the two doses was -181.206 mg in the 5-9 years of age group (CI 95 % -195.39; -167.02 mg) and -71.39 mg (CI 95 % -118.61; -23.99 mg) in the 10-14-year-old group. The CQ concentrations in blood on day 7 differed in patients over and under 15 years (p = 0.008). A negative correlation was found between the real and theoretical dose (difference in dose) and the age in years (R2 = 0.529, p = 0.001). A negative correlation was also found between the difference in dose (mg) and CQ concentrations on day 7 (ng/ml) (r = -0.337, p = 0.001). Children under 15 years were found to have a higher rate of therapeutic failure than those over 15 (28 vs 4.2 %, respectively) (Kaplan-Meier p = 0.005).

CONCLUSIONS

A CQ dose of 25 mg/kg for the treatment of P. vivax malaria may be too low in children as demonstrated by the reduction in CQ concentrations in blood at day 7 of follow-up. This under-dosage is probably associated with the higher rate of therapeutic failure found in children under 15 years (28 vs 4.3 %). These results suggest the need to review the paediatric doses of CQ currently used.

Failure of Oral Activated Charcoal to Accelerate the Elimination of Amiodarone and Chloroquine

1 The effect of activated charcoal on the elimination of amiodarone and chloroquine was studied in the rat.

2 The study consisted of two separate experiments. Amiodarone and chloroquine were injected subcutaneously at doses of 200 mg kg-1 and 100 mg kg-1, respectively. Six rats in both experiments were put on a charcoal-containing diet 48 h after drug administration, while the control groups remained on a normal diet.

3 Treatment with repeated oral activated charcoal had no effect on the true elimination of amiodarone and chloroquine.

4 These results suggest that, after the distribution of amiodarone and chloroquine into peripheral compartments, their rate of elimination cannot be significantly accelerated with multiple oral doses of activated charcoal.

Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases

OBJECTIVES

This review examines the pharmacokinetics, modes of action and therapeutic properties of the anti-malarial drugs, hydroxychloroquine (HCQ) and chloroquine (CQ), in the treatment of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and related conditions, as well as osteoarthritis (OA).

KEY FINDINGS

Both HCQ and CQ have historically been employed successfully for the treatment of SLE and RA for over 70 years. HCQ has been used extensively for SLE where it has a good reputation for controlling the dermatological complications in SLE. It has also been reported to effectively control the symptoms of Sjøgren's syndrome, as well as preventing thrombosis in phospholipid antibody (aPL) syndrome. In RA and SLE, HCQ is preferred because of the lower incidence of gastrointestinal adverse reactions compared with CQ and it might have a lower risk of ocular adverse reactions. There is increasing evidence that HCQ may reduce atherosclerosis and risks of cardiovascular disease in rheumatic patients. Both HCQ and CQ have been shown to improve glycaemia and reduce the risks of type II diabetes mellitus. Although both HCQ and CQ are effective in low-moderate RA, HCQ is now preferred as part of combination therapy for more severe disease. The advantages of combination therapy are that the doses of the individual drugs may be lowered so reducing adverse reactions. Both HCQ and CQ are diastereoisomers, have basic properties and are given as the sulphate and phosphate salts. While being relatively well absorbed orally and with good bioavailability, they have long and variable plasma terminal elimination half-lives (approximately 40-60 days). This reflects their high volume of distribution, V D (HCQ 44,000L; CQ 65,000L) which extends into aqueous compartments, long mean residence time (HCQ 1300 h; CQ 900 h) and with about half the drugs (metabolites) undergoing renal clearance. The strong binding to melanin reflects the ocular injury and dermatological properties of these drugs. The consensus is that the occurrence of ocular adverse reactions can be minimised by close attention to the dose (which should be set on a body weight basis) with regular (e.g. quarterly) retinal examination. Although HCQ and CQ can pass through the placenta, the use of these drugs during pregnancy does not appear to risk harm to the baby and might be beneficial to the mother with SLE and her child by controlling the SLE disease activity, which is known to be an important factor affecting pregnancy outcome. The modes of action of HCQ and CQ in these arthritides represent somewhat of an enigma. Undoubtedly, these drugs have multiple actions related, in part, their ability to accumulate in lysosomes and autophagosomes of phagocytic cells as well as affecting MHC Class II expression and antigen presentation; actions of the production of pro-inflammatory cytokines [e.g. interleukin-1 (IL-1) tumour necrosis factor-α (TNFα)]; control of toll-like receptor-9 activation; and leucocyte generation of reactive oxygen species (ROS); i.e. antioxidant activity. The actions of these drugs on T and B cells are less clear but may depend on these leucocyte-mediated actions. Anti-malarials also protect against cytokine-mediated cartilage resorption. This and other actions may underlie the potential benefits in treating OA. The exact relationships of these various actions, mostly determined in vitro, have not been specifically defined in vivo or ex vivo in relation to clinical efficacy.

OUTCOMES

HCQ and CQ have a good reputation for being effective and relatively safe treatments in SLE, mild-moderate RA and Sjøgren's syndrome. There is need for (a) more information on their mode of action in relation to the control of these diseases, (b) scope for developing formulations that have improved pharmacokinetic and therapeutic properties and safety, and (c) further exploring their use in drug combinations not only with other disease modifying agents but also with biologics.

Comparison of azithromycin plus chloroquine versus artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum malaria in children in Africa: a randomized, open-label study

BACKGROUND

This randomized, open-label study was conducted to establish the non-inferiority of a combination of azithromycin (AZ) and chloroquine (CQ) to artemether-lumefantrine (AL) for treatment of uncomplicated malaria in children from six sites in sub-Saharan Africa.

METHODS

Children with uncomplicated Plasmodium falciparum malaria between six and 59 months of age were randomized 1:1 to either AZCQ (30 mg/kg AZ + 10 mg/kg CQ base) or AL per prescribing information for three days (Days 0, 1, 2). Each site could enrol in the study population once the treatment of uncomplicated malaria in five children five to 12 years of age was deemed to be effective and well tolerated. The primary efficacy evaluation was the proportion of subjects in both the modified intent-to-treat (MITT) and per-protocol (PP) populations with an adequate clinical and parasitological response (PCR corrected) at Day 28. Non-inferiority was concluded if the lower bound of the 95% confidence interval comparing the two groups was 10 percentage points or greater.

RESULTS

A total of 255 children were enrolled in the efficacy analysis (AZCQ, n = 124; AL, n = 131). The PCR corrected clearance rates were 89% (AZCQ) versus 98% (AL) for MITT, a difference of -9.10 (95% confidence interval; -16.02, -2.18) and 93% (AZCQ) versus 99% (AL) for PP, a difference of -6.08 (-12.10, -0.05). Early and late treatment failures were more common in subjects receiving AZCQ. Adverse events were more common in subjects treated with AZCQ. Drug concentrations obtained at specified time points following AZCQ administration had a large coefficient of variation partially due to sparse sampling with sample collection time window.

CONCLUSIONS

In this study, non-inferiority of AZCQ to AL was not demonstrated.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00677833 .

Analysis of chloroquine and metabolites directly from whole-body animal tissue sections by liquid extraction surface analysis (LESA) and tandem mass spectrometry

The rapid and direct analysis of the amount and spatial distribution of exogenous chloroquine (CHQ) and CHQ metabolites from tissue sections by liquid extraction surface sampling analysis coupled with tandem mass spectrometry (LESA-MS/MS) was demonstrated. LESA-MS/MS results compared well with previously published CHQ quantification data collected by organ excision, extraction and fluorescent detection. The ability to directly sample and analyze spatially resolved exogenous molecules from tissue sections with minimal sample preparation and analytical method development has the potential to facilitate the assessment of target tissue penetration of pharmaceutical compounds, to establish pharmacokinetic/pharmacodynamic relationships, and to complement established pharmacokinetic methods used in the drug discovery process during tissue distribution assessment.

pH-sensitive capsules as intracellular optical reporters for monitoring lysosomal pH changes upon stimulation

The concept of a long-term sensor for ion changes in the lysosome is presented. The sensor is made by layer-by-layer assembly of oppositely charged polyelectrolytes around ion-sensitive fluorophores, in this case for protons. The sensor is spontaneously incorporated by cells and resides over days in the lysosome. Intracellular changes of the concentration of protons upon cellular stimulation with pH-active agents are monitored by read-out of the sensor fluorescence at real time. With help of this sensor concept it is demonstrated that the different agents used (Monensin, Chloroquine, Bafilomycin A1, Amiloride) possessed different kinetics and mechanisms of action in affecting the intracellular pH values.

Radical curative efficacy of tafenoquine combination regimens in Plasmodium cynomolgi-infected Rhesus monkeys (Macaca mulatta)

BACKGROUND

Tafenoquine is an 8-aminoquinoline being developed for radical cure (blood and liver stage elimination) of Plasmodium vivax. During monotherapy treatment, the compound exhibits slow parasite and fever clearance times, and toxicity in glucose-6-phosphate dehydrogenase (G6PD) deficiency is a concern. Combination with other antimalarials may mitigate these concerns.

METHODS

In 2005, the radical curative efficacy of tafenoquine combinations was investigated in Plasmodium cynomolgi-infected naïve Indian-origin Rhesus monkeys. In the first cohort, groups of two monkeys were treated with a three-day regimen of tafenoquine at different doses alone and in combination with a three-day chloroquine regimen to determine the minimum curative dose (MCD). In the second cohort, the radical curative efficacy of a single-day regimen of tafenoquine-mefloquine was compared to that of two three-day regimens comprising tafenoquine at its MCD with chloroquine or artemether-lumefantrine in groups of six monkeys. In a final cohort, the efficacy of the MCD of tafenoquine against hypnozoites alone and in combination with chloroquine was investigated in groups of six monkeys after quinine pre-treatment to eliminate asexual parasites. Plasma tafenoquine, chloroquine and desethylchloroquine concentrations were determined by LC-MS in order to compare doses of the drugs to those used clinically in humans.

RESULTS

The total MCD of tafenoquine required in combination regimens for radical cure was ten-fold lower (1.8 mg/kg versus 18 mg/kg) than for monotherapy. This regimen (1.8 mg/kg) was equally efficacious as monotherapy or in combination with chloroquine after quinine pre-treatment to eliminate asexual stages. The same dose of (1.8 mg/kg) was radically curative in combination with artemether-lumefantrine. Tafenoquine was also radically curative when combined with mefloquine. The MCD of tafenoquine monotherapy for radical cure (18 mg/kg) appears to be biologically equivalent to a 600-1200 mg dose in humans. At its MCD in combination with blood schizonticidal drugs (1.8 mg/kg), the maximum observed plasma concentrations were substantially lower than (20-84 versus 550-1,100 ng/ml) after administration of 1, 200 mg in clinical studies.

CONCLUSIONS

Ten-fold lower clinical doses of tafenoquine than used in prior studies may be effective against P. vivax hypnozoites if the drug is deployed in combination with effective blood-schizonticidal drugs.

Distribution of chloroquine in ocular tissue of pigmented rat using matrix-assisted laser desorption/ionization imaging quadrupole time-of-flight tandem mass spectrometry

In pharmacology and toxicology, localization of the distribution of a drug molecule in its target tissue provides very important in vivo biological information. Traditionally, this has been examined using autoradiography (ARG). However, there are significant limitations in this application. One is the synthesis and use of radiolabeled compounds, the other is that the image generated expresses an undifferentiated mixture of the parent drug and/or its metabolites. The objective of the study was to define the specific distribution of the parent drug in rat ocular tissue containing melanin (e.g. the retina) using non-labeled chloroquine by MALDI Imaging tandem mass spectrometry (MS/MS). After single oral administration (at 20 mg/kg) of chloroquine, sections (10 µm) of rat eye tissue were prepared at 24 h. The MS system used was a quadrupole time-of flight (Q-TOF) tandem mass spectrometer (MALDI Synapt™, Waters, Milford, MA, USA). Tissue sections were sprayed with CHCA (α-cyano-4-hydroxycinnamic acid, 5 mg/mL) in 80% acetonitrile (ACN) containing 5% formic acid (FA) using either a manual sprayer (airbrush) or an automated sprayer (TM-Sprayer™, HTX Technologies, Carrboro, NC, USA). Chloroquine was readily detected in the MS/MS mode by monitoring one of its major fragment ions (m/z 247.10) and imaged through the rat eye tissue. The image of the specific distribution within the retina in the rat eye tissue was confirmed, and found to be similar to autoradiograms after oral administration of (14)C-chloroquine reported previously.

An in-vitro study of chloroquine transport in the rat submaxillary gland

The uptake and efflux of chloroquine by the rat submaxillary gland in-vitro were studied under various incubation conditions. Variations in the extracellular pH significantly affected both the uptake and efflux of the drug. Increasing chloroquine concentration significantly decreased the uptake. Uptake was also decreased significantly (P < 0·05) when compared with control conditions (pH 7·40, 37·5°C, O2 aeration, 6 × 10−6  m chloroquine) by the following experimental variations: aeration of the incubation medium with N2 instead of O2; decrease of bath temperature from 37·5 to 4°C; addition of metabolic inhibitors, cyanide (10−3  m), iodoacetic acid (10−3  m) and o-nitrophenol (10−3  m). Cimetidine (10−3  m), a known organic cationic inhibitor, had no significant effect on chloroquine uptake when compared with control values. These results show that the uptake of chloroquine by the rat submaxillary gland in-vitro is concentration-dependent and this is indicative of possible saturable binding sites for the drug in the gland. These results suggest that the transfer of chloroquine across the submaxillary gland may be mediated by an active transport process. On the other hand, it is possible that the apparent active transport process implicated in this study could be a consequence of chloroquine ion trapping in the acidic interior of lysosomes.

Absorption, distribution and excretion of 14C-levofloxacin after single oral administration in albino and pigmented rats: binding characteristics of levofloxacin-related radioactivity to melanin in vivo

After single oral administration of 14C-levofloxacin at a dose of 20 mg kg−1 under non-fasting conditions, the absorption, distribution and excretion of radioactivity were studied in albino and pigmented rats. Good penetration of radioactivity into tissues was indicated by higher concentrations in most tissues compared with serum and there were no quantitative differences in the distribution of radioactivity between albino and pigmented rats except for melanin-containing tissues such as the uveal tract of eyes and hair follicles. There was selective and strong binding of drug-related radioactivity to these tissues in pigmented rats. The uveal tract concentrations reached the maximum value (Cmax) of 26.33 + 0.75 μg eq.g−1 at 24 h after dosing and declined slowly with a terminal half-life of 468.1 h (19.5 days). The uveal tract concentration at 12 weeks was 0.73 + 0.12 μg eq.g−1, which is c. 1/36 of Cmax. The AUC0-∞ for the uveal tract was 12.58 mg h−1 g−1. The uveal tracts separated from one eye of each rat were extracted with 0.067 m phosphate buffer (pH 7.4) and 1m HCl/EtOH (30:70), successively. In pigmented rats, approximately 85–48% of radioactivity bound to the uveal tract was released from the tissue by the washing procedures. Most of the eluted radioactivity was released with 1m HCl/EtOH (30:70), indicating that the binding to melanin is reversible, and hydrophobic and electrostatic interactions play an important role in the binding of levofloxacin and/or its metabolites with melanin-containing ocular tissues. Only unchanged drug was detected in the extracts of the uveal tracts. The concentrations and half-life of radioactivity in the uveal tract after dosing of 14C-levofloxacin were found to be much lower and shorter than those after dosing of 14C-chloroquine. It is unlikely that levofloxacin causes toxicity because of its much lower affinity to melanin-containing ocular tissues and shorter duration of therapy compared to chloroquine.

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.

Pharmacokinetic interactions between chloroquine, sulfadoxine and pyrimethamine and their bioequivalence in a generic fixed-dose combination in healthy volunteers in Uganda

BACKGROUND

A pre-packaged fixed-dose formulation of chloroquine (CQ) and sulfadoxine/pyrimethamine (S/P) combination (Homapak) is widely used for the treatment of falciparum malaria in Ugandan children. It is however a product whose pharmacokinetics and interactions have not been studied.

OBJECTIVES

To explore possible pharmacokinetic interactions between CQ and S/P during co-administration, and to determine their bioavailability in the locally made Homapak compared to the Good Manufacturing Practice (GMP) made formulations.

METHODS

Thirty-two adult healthy volunteers were randomized into four groups and given single oral doses of fixed-dose CQ+S/P combination (Homapak), or GMP formulations of S/P (Fansidar), CQ (Pharco), or their combination. Plasma samples were followed for 21 days, analysed by HPLC-UV methods, with pharmacokinetic modeling using the WinNonlin software.

RESULTS

Sulfadoxine in Homapak was more rapidly absorbed (ka = 0.55 h(-1)) than in Fansidar + CQ (ka = 0.27 h(-1), p=0.004), but not more than S in Fansidar alone group (ka = 0.32 h(-1), p=0.03). No significant differences were observed in the other pharmacokinetic parameters of S, P and CQ when given together or separately. The relative bioavailability of CQ and S in Homapak showed bioequivalence to reference formulations.

CONCLUSIONS

There were no pharmacokinetic interactions between CQ, S and P when the compounds were given together, however, more investigations would be needed to explore this further. Compared with GMP made drugs, both S and CQ are bioequivalent in Homapak, the Ugandan made fixed-dose formulation. Furthermore, the absorption of S was more rapid which could be advantageous in malaria treatment.

Systematic Delivery of Chloroquine and Promethazine Using pH-Sensitive Polymers

Two pH sensitive polymers (Eudragit L30 D55 and L100) were used as coating materials, respectively, for promethazine hydrochloride and chloroquine phosphate granules formulated with sodium carboxylmethylcellulose and Carbopol 940, respectively, in the ratios 1:1, 1:2, 1:3, and 1:4 (drug:polymer). The granules were characterized. Release studies for the uncoated and coated particles were studied in simulated gastric fluid and simulated intestinal fluid. Result obtained showed that 1:1 and 1:2 ratios of both coated and uncoated granules of the two drugs had short release times and could be recommended for rapid action, whereas 1:4 ratio with low release time could be used for sustained effect. The two granules could be used at varying ratios to obtain desired release characteristics, such that therapeutic concentrations of the two drugs could be achieved.

Antimalarials Inhibit Human Erythrocyte Membrane Acetylcholinesterase

The current study examined the ability of antimalarials chloroquine (CQ), primaquine (PQ), and quinine (Q) to inhibit human erythrocyte membrane acetylcholinesterase (AChE) and the mechanisms underlying their inhibitory action. CQ was found to be the most effective inhibitor of the enzyme followed by PQ and Q. The concentrations required to obtain 33% inhibition (IC(33)) for CQ and PQ were 22 and 38 microM, respectively, whereas that for Q was 3.2 mM. The concentrations required to obtain 67% inhibition (IC(67)) were about 9 and 7 times higher for CQ and PQ, whereas that for Q was only about 2.5 times higher. Hill plot analysis revealed that CQ shows de-binding above 40 microM. The two kinetic components of AChE were inhibited by the three antimalarials, and the inhibition was of mixed type. Increasing concentrations of antimalarials caused progressive decrease in the V(max) of both components. IC(33) concentrations resulted in 1.6- to 6-fold increase in K(m) of both the components while IC(67) concentration caused 2.8- to 13-fold increases in K(m) with maximum effect being seen with Q. The K(i) values were lowest for CQ suggesting that it was the most potent inhibitor; these values were 3.3 and 60 times higher for PQ and Q. Antimalarials represent the bifunctional compounds that possess anti-inflammatory properties and also inhibit cholinesterases. The results of our studies suggest that 4-aminoquinoline-based antimalarials like CQ and hydroxychloroquine, which are both potent anti-inflammatory agents and inhibitors of cholinesterases, may have potential use as the most effective neuroprotective agents against amyloid-beta-peptide (Abeta) neurotoxicity in Alzheimer's disease.

Pharmacokinetic determinants of the window of selection for antimalarial drug resistance

The selection and spread of antimalarial drug resistance pose enormous challenges to the health of people living in tropical countries. Most antimalarial drugs are slowly eliminated and so, following treatment in areas of endemicity, provide a gradient of concentrations to which newly acquired parasites are exposed. There is a variable period during which a new blood-stage infection with resistant malaria parasites can emerge from the liver and subsequently produce gametocyte densities sufficient for transmission while reinfection by sensitive parasites is still suppressed. This "window of selection" drives the spread of resistance. We have examined the factors which determine the duration of this window and, thus, the resistance selection pressure. The duration ranges from zero to several months and is dependent on the degree of parasite resistance, the slope of the concentration-effect relationship, and the elimination kinetics of the antimalarial drug. The time at which the window opens and the duration of opening are both linear functions of the terminal elimination half-life. Because of competition from sibling susceptible parasites, the greater risks of extinction with low starting numbers, and opening of the window only when blood concentrations have fallen below the MIC, the window of selection for de novo resistance is narrower than that for resistance acquired elsewhere. The windows were examined for the currently available antimalarials. Drugs with elimination half-lives of less than 1 day, such as the artemisinins and quinine, do not select for resistance during the elimination phase.

Immunohistochemical demonstration of the distribution of chloroquine (CQ) and its metabolites in CQ-poisoned mice

Chloroquine (CQ) distribution in tissues of acutely poisoned mice was demonstrated by immunohistochemistry using anti-CQ polyclonal antibodies (PAC). PAC recognized 4-amino-7-chloro-quinoline structure and sufficiently reacted with CQ and CQ's metabolite bisdesethyl-chloroquine. In the brain, CQ and its metabolites (CQs) localized in the region of the choroids plexus, indicating an important role in the blood-cerebrospinal barrier system. In the heart, most regions showed diffused positive staining, and relatively strong reaction was observed in Purkinje cells, indicating an important role in acute CQ toxicity. In the lungs, CQs were observed in the bronchial epithelium, type II pneumocytes, and on the surface of alveolar walls. It was suggested that CQs were excreted to the alveolar wall with surfactant phospholipids, which are produced by type II pneumocytes. In the liver, CQs were concentrated in the centrolobular area rather than in the periportal area, in agreement with CQ's metabolic pathway. In the kidneys, tubular cells were strongly stained compared to glomerular capsules, and the distal part of renal tubules was better stained than the proximal tubules. These findings suggested that CQs were predominantly excreted or reabsorbed through the distal tubules and the collecting duct. Distribution of CQs in tissues presented here were mostly consistent with the physico-chemical properties of CQ and its metabolites. However, the elucidation of CQs' localization in Purkinje cells remains open. Further experimental studies at the level of microorganella will be needed to clarify the present result.

Sensitive and rapid liquid chromatography/tandem mass spectrometric assay for the quantification of chloroquine in dog plasma

A simple, sensitive and rapid liquid chromatography/tandem mass spectrometric (LC-MS/MS) method was developed and validated for quantification of chloroquine, an antimalarial drug, in plasma using its structural analogue, piperazine bis chloroquinoline as internal standard (IS). The method is based on simple protein precipitation with methanol followed by a rapid isocratic elution with 10 mM ammonium acetate buffer/methanol (25/75, v/v, pH 4.6) on Chromolith SpeedROD RP-18e reversed phase chromatographic column and subsequent analysis by mass spectrometry in the multiple reaction monitoring mode (MRM). The precursor to product ion transitions of m/z 320.3-->247.2 and m/z 409.1-->205.2 were used to measure the analyte and the IS, respectively. The assay exhibited a linear dynamic range of 2.0-489.1 ng/mL for chloroquine in dog plasma. The limit of detection (LOD) and lower limit of quantification (LLOQ) were 0.4 and 2.0 ng/mL, respectively in 0.05 mL plasma. Acceptable precision and accuracy were obtained for concentrations over the standard curve range of 2.0-489.1 ng/mL. A run time of 2.0 min for a sample made it possible to achieve a throughput of more than 400 plasma samples analyzed per day. The validated method was successfully used to analyze samples of dog plasma during non-clinical study of chloroquine.

Quantitative assessment of seminal vesicle and prostate drug concentrations by use of a noninvasive method

BACKGROUND

The male genital tract is a complex collection of anatomically and biochemically distinct compartments that contribute to the ejaculate. Understanding the pharmacokinetics in these compartments should inform rational therapeutics involving these glands.

METHODS

Nineteen men were administered a single dose of 600 mg chloroquine (base) and 975 mg aspirin before providing a semen sample by masturbation with fractionation into a 5-compartment collection device. Fractions were assayed for fructose (unique seminal vesicle marker), prostate-specific antigen (unique prostate marker), salicylate, and chloroquine. Seminal vesicle and prostate concentrations of salicylate and chloroquine were estimated via a novel analytic method involving a multilevel latent-variable model implemented by use of Bayesian methods.

RESULTS

The geometric mean chloroquine semen/blood ratio was 4.02 (95% confidence interval [CI], 2.36-6.86); for salicylate, the primary metabolite of aspirin, the semen/blood ratio was 0.10 (95% CI, 0.08-0.14). The estimated mean prostate/seminal vesicle ratio for salicylate, 0.38 (95% CI by Bayesian methods, 0.12-0.73), was consistent with our hypothesis that salicylate would achieve higher concentrations in the seminal vesicle than in the prostate. Chloroquine, however, did not demonstrate a statistically significant seminal vesicle/prostate difference (4.41; 95% CI by Bayesian methods, 0.14-30.52).

CONCLUSIONS

We successfully demonstrated the quantitative, noninvasive estimation of drug concentrations in the prostate gland fluid distinct from the seminal vesicle fluid using our optimized method of split-ejaculate collection and a novel mixed-effects model with Bayesian estimation. Our methods can be applied to gland-specific quantitation of drugs and other substances of interest, thus enabling pharmacokinetic, pharmacodynamic, and pathophysiologic studies to inform rational therapeutics within different glands of the male genital tract.

Lack of a pharmacokinetic interaction between azithromycin and chloroquine

A study was conducted to investigate a possible pharmacokinetic interaction between azithromycin and chloroquine. Twenty-four subjects received azithromycin, 1,000 mg a day for three days, followed by a washout period, then azithromycin, 1,000 mg plus chloroquine 600 mg base on days 1 and 2, and azithromycin, 1,000 mg plus chloroquine 300 mg base on day 3 of the final period. A second group of 16 subjects received chloroquine, 600 mg base on days 1 and 2, then 300 mg base on day 3. Blood samples were obtained serially up to 624 hours after the day 3 dose in each period. Log transformed maximum concentration and area under the curve values of azithromycin and chloroquine were compared using 90% confidence intervals calculated from appropriate analysis of variance models. Ninety percent confidence intervals for all pharmacokinetic parameters were contained within the interval 80-125%, which indicates the absence of a clinically relevant pharmacokinetic interaction.

El citocromo P-450 y la respuesta terapéutica a los antimaláricos

OBJECTIVES

To assess the relationship between the genetic and phenotypic factors linked to the cytochrome P-450 enzyme system and the response to the antimalarial drugs chloroquine, amodiaquine, mefloquine, and proguanil, as well as to determine how certain biological and social factors of the host influence the behavior of this enzymatic complex.

METHODS

We performed a systematic review of the medical bibliographic databases PubMed, Excerpta Medica, LILACS, and SciELO by using the following Spanish and English descriptors: "CYP-450" and "citocromo P-450" in combination with "proguanil" (and with "mefloquina," "cloroquina," and "amodiaquina"), "farmacocinética de proguanil" (and the same using "mefloquina," "cloroquina," and "amodiaquina"), "resistencia a proguanil" (and the same using "mefloquina," "cloroquina," and "amodiaquina"), "metabolismo," "farmacogenética," "enfermedad," "inflamación," "infección," "enfermedad hepática," "malaria," "nutrición," and "desnutrición." The same terms were used in English. The search included only articles published in Spanish, English, and Portuguese on or before 30 June 2005 that dealt with only four antimalarial drugs: amodiaquine, chloroquine, mefloquine, and proguanil.

RESULTS

Some genetic factors linked to human cytochrome P-450 (mainly its polymorphism), as well as other biological and social factors (the presence of disease itself, or of inflammation and infection, the use of antimalarials in their various combinations, and the patient's nutritional status) influence the behavior of this complex enzymatic system. It has only been in the last decade that the genetics of the cytochromes has been explored and that the mechanisms underlying some therapeutic interactions and aspects of drug metabolism have been uncovered, making it possible to characterize the biotransformation pathway of amodiaquine and chloroquine. Hopefully new research will help answer the questions that still remain, some of which pertain to the metabolism of other antimalarial drugs, the distribution in the population of the genetic alleles linked to the enzymes involved in their metabolism, the contribution of these genetic mutations to therapeutic failure, and the possibility of predicting the response to antimalarial therapy.

CONCLUSIONS

The therapeutic response to antimalarial drugs is a multifactorial process that is poorly understood, so that it is not possible to ascribe to a specific phenotype or genotype a role in the response to antimalarial therapy. Attention should be given to biological and social factors, such as diet, nutritional status, and inflammatory and infectious processes that are often present in areas where malaria is endemic.

PEGylated Peptide Dendrimeric Carriers for the Delivery of Antimalarial Drug Chloroquine Phosphate

PURPOSE

The present study was aimed at developing and exploring the use of uncoated and chondroitin sulfate A (CSA) coated PEGylated poly-L-lysine-based dendrimers for controlled and sustained delivery of a blood schizonticide, chloroquine phosphate (CQ).

METHODS

The poly-L-lysine-based peptide dendrimers with PEG amine core prepared and coated with CSA were used to encapsulate the drug molecules by dialysis method. Effect of CSA coating on the surface characteristics, drug entrapment, drug release, stability, hemolytic toxicity, macrophageal interactions, and cytoadherence were determined and compared with those of uncoated systems.

RESULTS

The CSA coating of the carriers was found to increase size and drug loading capacity, and reduce drug release rate and hemolytic toxicity. Transmission electron microscopic study revealed the surface properties of the systems. Stability studies had shown increased stability of the formulations on CSA coating. There was a significant reduction in hemolytic toxicity and cytotoxicity of CQ by the present dendrimeric carriers, which became more prominent on further CSA conjugation of the equivalent drug-loaded dendrimeric carriers. There were also significant reduction in levels of ring and trophozoite stages of Plasmodium falciparum in liquid culture when treated with CSA coated dendrimers because of the expression of similar carbohydrate receptors as that by placental and cerebral barriers for infected red blood cells. The systems were also found suitable for prolonging and controlling the blood level of drug as indicated by blood level and organ distribution studies in albino rats on intravenous administration, precluding any significant hematological or toxicological manifestations.

CONCLUSION

Thus it can be said that CSA coating can improve drug-loading capacity, control and sustain the release of CQ from such carriers, and can suitably act as safer and effective carriers for intravenous CQ administration.

Antipaludéens de synthèse

The antimalarials, mainly chloroquine and hydroxychloroquine, derive from the quinoleine core of quinine. Their initial therapeutic indication was the treatment of malaria attacks but, because of anti-inflammatory and immuno-modulatory activities, they have been since used to treat many other pathologies, in particular dermatological ones. For some of these pathologies, lupus or porphyria cutanea tarda for example, the use of these molecules is based on obvious scientific evidence. For other pathologies (cutaneous sarcoidosis, polymyositis, polymorphous light eruption...), the data on the medical literature corroborating the daily clinical practice are extremely poor. Their toxicity is limited. Their most common toxic effects are gastrointestinal (mild nausea or diarrhea) or mucocutaneous (reversible skin or mucosal pigmentation). Their most serious and dreaded side effect, retinopathy, can be largely prevented by using amounts of APS adapted to the weight of the patients. The recommended "safe" daily dose for hydroxychloroquine is 6.5 mg per kilogramme of body weight and for chloroquine 4 mg per kilogramme of body weight. However, at 6- to 12 months intervals, follow-up eye examinations should be performed.

Reversal of chloroquine resistance in Plasmodium falciparum by 9H-xanthene derivatives

Four new chemosensitisers against chloroquine-resistant Plasmodium falciparum based on the 9H-xanthene tricyclic scaffold were designed and synthesised in an attempt to identify simplified compounds that are easily accessible from commercially available starting materials. The compounds contain a common hydrophobic tricyclic 9H-xanthene moiety and an alkyl side chain with two amino groups, one of which is a tertiary substituted terminal amine, separated by three carbons and differing only in the chemical nature of the intermediary nitrogen atom. The best chemosensitising compound has a secondary amino group, showed a response modification index of 0.36 and caused a four-fold increase in chloroquine accumulation in a resistant strain of P. falciparum as well as having the highest selective therapeutic index when tested against a mammalian cell line.

Dictyostelium discoideum expresses a malaria chloroquine resistance mechanism upon transfection with mutant, but not wild-type, Plasmodium falciparum transporter PfCRT

Chloroquine resistance in Plasmodium falciparum malaria results from mutations in PfCRT, a member of a unique family of transporters present in apicomplexan parasites and Dictyostelium discoideum. Mechanisms that have been proposed to explain chloroquine resistance are difficult to evaluate within malaria parasites. Here we report on the targeted expression of wild-type and mutant forms of PfCRT to acidic vesicles in D. discoideum. We show that wild-type PfCRT has minimal effect on the accumulation of chloroquine by D. discoideum, whereas forms of PfCRT carrying a key charge-loss mutation of lysine 76 (e.g. K76T) enable D. discoideum to expel chloroquine. As in P. falciparum, the chloroquine resistance phenotype conferred on transformed D. discoideum can be reversed by the channel-blocking agent verapamil. Although intravesicular pH levels in D. discoideum show small acidic changes with the expression of different forms of PfCRT, these changes would tend to promote intravesicular trapping of chloroquine (a weak base) and do not account for reduced drug accumulation in transformed D. discoideum. Our results instead support outward-directed chloroquine efflux for the mechanism of chloroquine resistance by mutant PfCRT. This mechanism shows structural specificity as D. discoideum transformants that expel chloroquine do not expel piperaquine, a bisquinoline analog of chloroquine used frequently against chloroquine-resistant parasites in Southeast Asia. PfCRT, nevertheless, may have some ability to act on quinine and quinidine. Transformed D. discoideum will be useful for further studies of the chloroquine resistance mechanism and may assist in the development and evaluation of new antimalarial drugs.

Are 1–2 dangerous? Chloroquine and hydroxychloroquine exposure in toddlers

Ingestion of 1-2 tablets of chloroquine or hydroxylchloroquine is thought to predispose children under 6 years of age to serious morbidity and mortality. The actual risk to the toddler and appropriate guidelines for care remain unclear at a time when both medications are therapeutically utilized as anti-inflammatory agents in addition to their main use as anti-parasitics. A review of the literature and data from the American Association of Poison Control Centers reveals instances where exposure to as little as 1-2 tablets of chloroquine resulted in serious consequences. Based on these findings, ingestions of greater than 10 mg/kg of chloroquine base or unknown amounts require triage to the nearest health care facility for 4-6 h of observation. There is very limited data on pediatric hydroxychloroquine overdoses and no reports of toxicity from 1-2 pills, but given its similarity to chloroquine, it also should be considered potentially toxic at small doses. Thus, similar recommendations should be followed for triage after accidental hydroxychloroquine overdose.

HPLC analysis of anti-malaria agent, chloroquine in blood and tissue from forensic autopsy cases in Tanzania

HPLC analysis of anti-malaria agent, chloroquine (CQ) in blood and tissues with a simple HCl back extraction method was applied to three forensic autopsy cases in Dar es Salaam, Tanzania. CQ concentrations in femoral vein blood were 8.5, 48.4 and 43.8 microg/ml in three cases, respectively, which were high enough to attribute the cause of deaths to an acute CQ poisoning. There were great site dependent variations in blood CQ levels. The right heart blood samples were very high, which may be explained by incomplete distribution of the drug before death or postmortem diffusion from liver and its surrounding blood, as high CQ levels were remarkable in the liver. Suicidal and accidental CQ poisonings are very common and CQ is a very important chemical in the field of forensic toxicology in Tanzania.

Evidence for a Substrate Specific and Inhibitable Drug Efflux System in Chloroquine Resistant Plasmodium falciparum Strains

The mechanism underpinning chloroquine drug resistance in the human malarial parasite Plasmodium falciparum remains controversial. By investigating the kinetics of chloroquine accumulation under varying-trans conditions, we recently presented evidence for a saturable and energy-dependent chloroquine efflux system present in chloroquine resistant P. falciparum strains. Here, we further characterize the putative chloroquine efflux system by investigating its substrate specificity using a broad range of different antimalarial drugs. Our data show that preloading cells with amodiaquine, primaquine, quinacrine, quinine, and quinidine stimulates labeled chloroquine accumulation under varying-trans conditions, while mefloquine, halofantrine, artemisinin, and pyrimethamine do not induce this effect. In the reverse of the varying-trans procedure, we show that preloaded cold chloroquine can stimulate quinine accumulation. On the basis of these findings, we propose that the putative chloroquine efflux system is capable of transporting, in addition to chloroquine, structurally related quinoline and methoxyacridine antimalarial drugs. Verapamil and the calcium/calmodulin antagonist W7 abrogate stimulated chloroquine accumulation and energy-dependent chloroquine extrusion. Our data are consistent with a substrate specific and inhibitible drug efflux system being present in chloroquine resistant P. falciparum strains.

Comparative assessment of ocular tissue distribution of drug-related radioactivity after chronic oral administration of 14C-levofloxacin and 14C-chloroquine in pigmented rats

Fluoroquinolones have been reported to have a high affinity for melanin. The ocular tissue distribution and accumulation of radioactivity was compared after repeated oral administration of 14C-levofloxacin and 14C-chloroquine at daily doses of 20 mg (0.054 mmol) kg(-1) and 28 mg (0.054 mmol) kg(-1), respectively, in pigmented rats for 84 days. The mean serum level at 24 h following each dose of 14C-levofloxacin was almost constant in the range of 0.33-0.45 nmol equiv mL(-1) after the 14th dose and thereafter. The melanin-containing ocular tissues, such as iris ciliary body and stratum pigment chorioides sclera, showed a much higher concentration of radioactivity than other non-pigmented ocular tissues. The respective concentration in iris ciliary body and stratum pigment chorioides sclera after the 1st dose was 126.47 and 74.91 nmol equiv g(-1), and gradually increased with increasing dose number, reaching 1261.81 and 447.45 nmol equiv g(-1) after the 84th dose, which was ca. 10 and 6 times higher, respectively, than after the 1st dose. The mean serum level following each dose of 14C-chloroquine was almost constant in the range 0.51-0.87 nmol equiv mL(-1) after the 7th dose and thereafter. The respective concentration in iris ciliary body and stratum pigment chorioides sclera after the 1st dose was 572.10 and 709.41 nmol equiv g(-1), and gradually increased with increasing dose number, reaching 33 317.92 and 12 322.90 nmol equiv g(-1) after the 84th dose, which was ca. 58 and 17 times higher, respectively, than after the 1st dose. The concentration in aqueous humour, cornea, lens, vitreous body and retina after the 84th dose was 1.84, 6.33, 0.48, 5.60 and 11.42 nmol equiv g(-1) for 14C-levofloxacin and 18.84, 264.99, 27.26, 158.43 and 1020.89 nmol equiv g(-1) for 14C-chloroquine (ca. 10, 42, 57, 28 and 89 times higher, respectively, than for 14C-levofloxacin). Especially, the concentration in the retina was markedly higher after 14C-chloroquine administration than after 14C-levofloxacin administration. The concentration and the extent of accumulation of radioactivity not only in melanin-containing ocular tissues but also in other non-pigmented ocular tissues, such as retina, after chronic oral administration of 14C-levofloxacin once daily for 84 days were much lower than those after multiple dosing with 14C-chloroquine under the same conditions. These results indicate that levofloxacin would have a much lower risk for ocular toxicity than chloroquine after chronic dosing.

Pharmacokinetic interaction of chloroquine and methylene blue combination against malaria

OBJECTIVE

The combination of chloroquine and methylene blue is potentially effective for the treatment of chloroquine-resistant malaria caused by Plasmodium falciparum. The aim of this study was to investigate whether methylene blue influences the pharmacokinetics of chloroquine.

METHODS

In a randomized, placebo-controlled, parallel group design, a 3-day course of therapeutic oral doses of chloroquine (total 2.5 g in male, 1.875 g in female participants) with oral co-administration of placebo or 130 mg methylene blue twice daily for 3 days was administered to 24 healthy individuals. Chloroquine, desethylchloroquine, and methylene blue concentrations were determined by means of HPLC/UV or LC/MS/MS assays in whole blood, plasma, and urine for 28 days after the last dose.

RESULTS

During methylene blue exposure, the area under the chloroquine whole blood concentration-time curve normalized to body weight (AUC(0-24 h)/BW) yielded a trend of reduction (249+/-98.2 h mug l(-1) kg(-1) versus 315+/-65.0 h mug l(-1) kg(-1), P=0.06). The AUC(0-24 h)/BW of desethylchloroquine was reduced by 35% (104+/-40.3 h mug l(-1) kg(-1) versus 159+/-66.6 h mug l(-1) kg(-1), P=0.03), whereas the metabolic ratio between chloroquine and desethylchloroquine remained unchanged (2.25+/-0.49 versus 1.95+/-0.42, P=0.17). The renal clearance of chloroquine and the ratio between chloroquine in whole blood and plasma remained unchanged (P>0.1).

CONCLUSION

Oral co-administration of methylene blue appears to result in a small reduction of chloroquine exposure which is not expected to be clinically relevant and thus represents no concern for further development as an anti-malarial combination.

Absorption, distribution and excretion of 14C-chloroquine after single oral administration in albino and pigmented rats: binding characteristics of chloroquine-related radioactivity to melanin in-vivo

Chloroquine is an antimalarial agent that has been reported to have distinct affinity to melanin. After single oral administration of 14C-chloroquine at a dose of 20mg kg-1 under non-fasting conditions, the absorption, distribution and excretion of 14C-chloroquine-related radioactivity were studied in albino and pigmented rats. The objectives of the study were to investigate differences in the disposition of chloroquine between albino and pigmented rats and to define its in-vivo binding characteristics to melanin-containing ocular tissues. Extensive uptake of radioactivity into tissues was indicated by higher concentrations in most tissues compared with serum and there was no quantitative differences in the distribution of radioactivity found between albino and pigmented rats except for melanin-containing tissues, such as the uveal tract of the eye and perhaps hair follicles. There was selective and strong binding of drug-related compounds to these tissues in pigmented rats. The uveal tract concentrations reached the maximum value of 158.42 +/- 7.86 micrograms equiv g-1 (mean+/-s.e.) at 1 week and decreased very slowly with a terminal half life of 4476 h (187 day). The uveal tract concentrations at 24 weeks were still high (67.75 +/- 6.19 micrograms equiv g-1). The AUC for uveal tract was 842.3 mg.h g-1. A relatively high concentration was still determined in the uveal tract even at 48 weeks after single oral dosing by whole-body autoradiography. The uveal tracts separated from one eye of each rat were extracted with 0.067 M phosphate buffer (pH 7.4) and 1 M HCl-EtOH (30:70) successively. In pigmented rats, almost all radioactivity was released from the tissue with 1 M HCl-EtOH (30:70), indicating that the strong binding by melanin was reversible, and that hydrophobic or electrostatic interaction would play a critical role in the binding of chloroquine and its metabolites with the melanin-containing ocular tissues. Approximately 70% of the radioactivity given was recovered in urine and faeces up to 144 h after dosing both in pigmented and albino rats. The excretion pattern in pigmented rats was similar to that seen in albino rats.

Interaction between chloroquine sulphate and aqueous extract of Azadirachta indica A. Juss (Meliaceae) in rabbits

This study was carried out to investigate the effect of concurrent oral administration of aqueous leaf extract of Azadirachta indica (Meliaceae) on the pharmacokinetic properties of chloroquine sulphate in experimental rabbits. The results indicated that concurrent administration of both agents resulted in a significant decrease in serum concentration, slower absorption and elimination as well as longer half-life of chloroquine sulphate. The highest relative decrease of 78.0% was recorded 4 hours after concurrent administration, while the smallest decrease (64.6%) occurred 24 hours after concurrent administration. Significant reductions were also noted in some pharmacokinetic parameters of chloroquine and included the area under the curve (71.9%), maximum serum concentration (69.8%), absorption rate constant (37.3%), elimination rate constant (53.9%), clearance rate (76.5%) and volume of distribution (47.2%). However, there was a pronounced increase in the half-life of the drug (125.7%).

[Studies on pharmacokinetics of chloroquine in mice infected with chloroquine-resistant strain of Plasmodium berghei]

OBJECTIVE

To compare the pharmacokinetic differences of chloroquine in normal mice and the mice infected with the N and the RC strains of Plasmodium berghei.

METHODS

The concentrations of chloroquine in the plasma of normal mice and the mice infected with the N or the RC strains of P. berghei were analyzed by reverse-phase HPLC. The pharmacokinetic parameters were measured with software 3P87.

RESULTS

The t1/2 beta value was significantly lower in the mice infected with the RC strain than in normal mice and the mice infected with the N strain(P < 0.05), however, there were no significant differences between the mice infected with the N strain and normal mice.

CONCLUSION

Elimination of chloroquine in the mice infected with the RC strain of P. berghei speed up significantly comparing with the mice infected with the N strain.

The relationship of physico-chemical properties and structure to the differential antiplasmodial activity of the cinchona alkaloids

Background

The 8-amino and 9-hydroxy substituents of antimalarial cinchona alkaloids have the erythro orientation while their inactive 9-epimers are threo. From the X-ray structures a 90° difference in torsion angle between the N1-H1 and C9-O12 bonds in the two series is believed to be important. In order to kill the malaria parasite, alkaloids must cross the erythrocyte and parasite membranes to accumulate in the acid digestive vacuole where they prevent detoxication of haematin produced during haemoglobin breakdown.

Methods

Ionization constants, octanol/water distribution and haematin interaction are examined for eight alkaloids to explain the influence of small structural differences on activity.

Results

Erythro isomers have a high distribution ratio of 55:1 from plasma to the erythrocyte membrane, while for the more basic threo epimers this is only 4.5:1. This gives an increased transfer rate of the erythro drugs into the erythrocyte and thence into the parasite vacuole where their favourable conformation allows interaction with haematin, inhibiting its dimerization strongly (90 ± 7%) and thereby killing the parasite. The threo compounds not only enter more slowly but are then severely restricted from binding to haematin by the gauche alignment of their N1-H1 and C9-O12 bonds. Confirmatory molecular models allowed measurement of angles and bond lengths and computation of the electronic spectrum of a quinine-haematin complex.

Conclusion

Differences in the antiplasmodial activity of the erythro and threo cinchona alkaloids may therefore be attributed to the cumulative effects of lipid/aqueous distribution ratio and drug-haematin interaction. Possible insights into the mechanism of chloroquine-resistance are discussed.