STUDIES ON THE PHARMACOLOGY OF CHLOROQUINE. RECOMMENDATIONS FOR THE TREATMENT OF CHLOROQUINE RETINOPATHY

The Impact of Systemic Medications on Retinal Function

This study will provide a thorough review of systemic (and select intravitreal) medications, along with illicit drugs that are capable of causing various patterns of retinal toxicity. The diagnosis is established by taking a thorough medication and drug history, and then by pattern recognition of the clinical retinal changes and multimodal imaging features. Examples of all of these types of toxicity will be thoroughly reviewed, including agents that cause retinal pigment epithelial disruption (hydroxychloroquine, thioridazine, pentosan polysulfate sodium, dideoxyinosine), retinal vascular occlusion (quinine, oral contraceptives), cystoid macular edema/retinal edema (nicotinic acid, sulfa-containing medications, taxels, glitazones), crystalline deposition (tamoxifen, canthaxanthin, methoxyflurane), uveitis, miscellaneous, and subjective visual symptoms (digoxin, sildenafil). The impact of newer chemotherapeutics and immunotherapeutics (tyrosine kinase inhibitor, mitogen-activated protein kinase kinase, checkpoint, anaplastic lymphoma kinase, extracellular signal-regulated kinase inhibitors, and others), will also be thoroughly reviewed. The mechanism of action will be explored in detail when known. When applicable, preventive measures will be discussed, and treatment will be reviewed. Illicit drugs (cannabinoids, cocaine, heroin, methamphetamine, alkyl nitrite), will also be reviewed in terms of the potential impact on retinal function.

Quantitative Fundus Autofluorescence in Systemic Chloroquine/Hydroxychloroquine Therapy

Purpose

To investigate the effect of systemic chloroquine/hydroxychloroquine (CQ/HCQ) on outer retinal health using quantitative fundus autofluorescence (QAF) imaging.

Methods

For this prospective, cross-sectional study, 44 CQ/HCQ patients and 25 age-matched controls underwent multimodal retinal imaging including QAF (488 nm) and spectral-domain optical coherence tomography (SD-OCT) in addition to the recommended CQ/HCQ screening procedures. Custom written FIJI plugins enabled detailed QAF analysis and correlation with retinal thickness and comparison to the healthy controls.

Results

Out of 44 patients, 29 (mean age 43.5 ± 12.2, range 22–59 years) exposed to CQ/HCQ (mean cumulative dose 724.2 ± 610.4 g, median 608.0 g, range 18.6–2171.0 g) met eligibility criteria. Four of these 29 patients had bull's-eye maculopathy (BEM). Mean QAF values were significantly higher in CQ/HCQ patients than in healthy controls. QAF increase started early after treatment onset, remained high even years after treatment cessation, and was not accompanied by pathologies in the other screening methods, including retinal thicknesses (except in BEM patients).

Conclusions

QAF might be a useful tool in retinal imaging and in verifying systemic CQ/HCQ intake. The early onset and preserved high levels of QAF parallel findings of CQ deposition in the retina in animal models. Whether QAF can be used as a screening tool to detect early CQ/HCQ related maculopathy is the subject of long-term ongoing studies.

Translation Relevance

Experimental QAF imaging in systemic CQ/HCQ therapy monitoring might be a useful tool to indicate the drug or its metabolites and to detect metabolic retinal changes.

Review on the Clinical Pharmacology of Hydroxychloroquine Sulfate for the Treatment of COVID-19

BACKGROUND

As the number of severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infected people is greatly increasing worldwide, the international medical situation becomes very serious. Potential therapeutic drugs, vaccine and stem cell replacement methods are emerging, so it is urgent to find specific therapeutic drugs and the best treatment regimens. After the publications on hydroxychloroquine (HCQ) with anti- SARS-COV-2 activity in vitro, a small, non-randomized, open-label clinical trial showed that HCQ treatment was significantly associated with reduced viral load in patients with coronavirus disease-19 (COVID-19). Meanwhile, a large prophylaxis study of HCQ sulfate for COVID-19 has been initiated in the United States. HCQ offered a promising efficacy in the treatment of COVID-19, but the optimal administration is still being explored.

METHODS

We used the keyword "hydroxychloroquine" to conduct a literature search in PubMed to collect relevant literature on the mechanism of action of HCQ, its clinical efficacy and safety, pharmacokinetic characteristics, precautions for clinical use and drug interactions to extract and organize information.

RESULTS

This paper reviews the mechanism, clinical efficacy and safety, pharmacokinetic characteristics, exposureresponse relationship and precautions and drug interactions of HCQ, and summarizes dosage recommendations for HCQ sulfate.

CONCLUSION

It has been proved that HCQ, which has an established safety profile, is effective against SARS-CoV-2 with sufficient pre-clinical rationale and evidence. Data from high-quality clinical trials are urgently needed worldwide.

Dose Optimization of Chloroquine by Pharmacokinetic Modeling During Pregnancy for the Treatment of Zika Virus Infection

The insidious nature of Zika virus (ZIKV) infections can have a devastating consequence for fetal development. Recent reports have highlighted that chloroquine (CQ) is capable of inhibiting ZIKV endocytosis in brain cells. We applied pharmacokinetic modeling to develop a predictive model for CQ exposure to identify an optimal maternal/fetal dosing regimen to prevent ZIKV endocytosis in brain cells. Model validation used 13 nonpregnancy and 3 pregnancy clinical studies, and a therapeutic CQ plasma window of 0.3-2 μM was derived. Dosing regimens used in rheumatoid arthritis, systemic lupus erythematosus, and malaria were assessed for their ability to target this window. Dosing regimen identified that weekly doses used in malaria were not sufficient to reach the lower therapeutic window; however, daily doses of 150 mg achieved this therapeutic window. The impact of gestational age was further assessed and culminated in a final proposed regimen of 600 mg on day 1, 300 mg on day 2 and 3, and 150 mg thereafter until the end of trimester 2, which resulted in maintaining 65% and 94% of subjects with a trough plasma concentration above the lower therapeutic window on day 6 and at term, respectively.

Management of relapsing Plasmodium vivax malaria

Introduction: Relapses are important contributors to illness and morbidity in Plasmodium vivax and P. ovale infections. Relapse prevention (radical cure) with primaquine is required for optimal management, control and ultimately elimination of Plasmodium vivax malaria. A review was conducted with publications in English, French, Portuguese and Spanish using the search terms ‘P. vivax’ and ‘relapse’.

Areas covered: Hypnozoites causing relapses may be activated weeks or months after initial infection. Incidence and temporal patterns of relapse varies geographically. Relapses derive from parasites either genetically similar or different from the primary infection indicating that some derive from previous infections. Malaria illness itself may activate relapse. Primaquine is the only widely available treatment for radical cure. However, it is often not given because of uncertainty over the risks of primaquine induced haemolysis when G6PD deficiency testing is unavailable. Recommended dosing of primaquine for radical cure in East Asia and Oceania is 0.5 mg base/kg/day and elsewhere is 0.25 mg base/kg/day. Alternative treatments are under investigation.

Expert commentary: Geographic heterogeneity in relapse patterns and chloroquine susceptibility of P. vivax, and G6PD deficiency epidemiology mean that radical treatment should be given much more than it is today. G6PD testing should be made widely available so primaquine can be given more safely.

[SD-OCT As screening test for hydroxychloroquine retinopathy: The «flying saucer» sign]

CASE REPORTS

Two asymptomatic women treated with hydroxychloroquine 200mg every day for 8 and 16 years developed retinal toxicity.

DISCUSSION

Patient 1 was found to have a normal fundus and autofluorescence examination. Patient 2 was found to have a completely normal fundus examination. Fluorescein angiography shows parafoveal hyperfluorescence, and autofluorescence shows a minimal decrease in signal in the same region. In both patients the SD-OCT shows disruption of the ellipsoid zone in parafoveal region («flying saucer» sign). SD-OCT findings in the retina can identify hydroxychloroquine retinopathy in asymptomatic patients.

Pharmacology of Chloroquine and Hydroxychloroquine

The 4-aminoquinolines are weak bases that are completely absorbed from the gastrointestinal tract, sequestered in peripheral tissues, metabolized in the liver to pharmacologically active by-products, and excreted via the kidneys and the feces. The parent drugs and metabolites are excreted with a half-life of elimination of approximately 40 days. However, slow release from sequestered stores of the drugs means that after discontinuation, they continue to be released into the plasma for years. Correct dosing is based on the ideal body weight of the patient, which depends on height. The 4AQs diminish autoimmunity without compromising immunity to infections.

Antiviral activity of chloroquine against human coronavirus OC43 infection in newborn mice

Until recently, human coronaviruses (HCoVs), such as HCoV strain OC43 (HCoV-OC43), were mainly known to cause 15 to 30% of mild upper respiratory tract infections. In recent years, the identification of new HCoVs, including severe acute respiratory syndrome coronavirus, revealed that HCoVs can be highly pathogenic and can cause more severe upper and lower respiratory tract infections, including bronchiolitis and pneumonia. To date, no specific antiviral drugs to prevent or treat HCoV infections are available. We demonstrate that chloroquine, a widely used drug with well-known antimalarial effects, inhibits HCoV-OC43 replication in HRT-18 cells, with a 50% effective concentration (+/- standard deviation) of 0.306 +/- 0.0091 microM and a 50% cytotoxic concentration (+/- standard deviation) of 419 +/- 192.5 microM, resulting in a selectivity index of 1,369. Further, we investigated whether chloroquine could prevent HCoV-OC43-induced death in newborn mice. Our results show that a lethal HCoV-OC43 infection in newborn C57BL/6 mice can be treated with chloroquine acquired transplacentally or via maternal milk. The highest survival rate (98.6%) of the pups was found when mother mice were treated daily with a concentration of 15 mg of chloroquine per kg of body weight. Survival rates declined in a dose-dependent manner, with 88% survival when treated with 5 mg/kg chloroquine and 13% survival when treated with 1 mg/kg chloroquine. Our results show that chloroquine can be highly effective against HCoV-OC43 infection in newborn mice and may be considered as a future drug against HCoVs.

Cardiomyopathy after chloroquine treatment

A case of cardiomyopathy combined with vacuolar myopathy in the extremity muscles and irreversible retinopathy produced by chloroquine is described.

Hemoperfusion is ineffectual in severe chloroquine poisoning

OBJECTIVES

To study the toxicokinetics in severe chloroquine poisoning, and to evaluate the efficacy of hemoperfusion.

DESIGN

Case report on one observation.

SETTING

Medical intensive care unit (ICU) of the University Medical Center Utrecht, The Netherlands.

PATIENT HISTORY

A previously healthy, 52-yr-old woman ingested 100 tablets containing 100 mg chloroquine base 1 hr before admission. At admission, she was drowsy, agitated, hypotensive, and in respiratory distress. Shortly thereafter, she was resuscitated from cardiac arrest. After hemodynamic and respiratory stabilization, the patient was transferred to the medical ICU. TOXICOKINETICS EVALUATION: During the course of her stay at the ICU, blood samples were taken for the determination of chloroquine and the metabolite desethylchloroquine concentration. Hemoperfusion was started 3.5 hrs after ingestion of the chloroquine tablets.

MEASUREMENTS AND MAIN RESULTS

The following toxicokinetics data during this severe chloroquine poisoning were calculated: apparent volume of the central compartment 181 L, apparent volume of distribution 1137 L, half-life in the distribution phase 6.4 hrs, half-life in the elimination phase 392.8 hrs, and total body clearance 2.01 L/hour. The average extraction ratio during hemoperfusion was 0.07, 0.28, and 0.25, in plasma, erythrocytes and whole blood, respectively. The total amount of chloroquine removed by hemoperfusion was only 480 mg (5.3% of the amount ingested). Simulation of a hemoperfusion session over 5 hrs by using a column with an optimal extraction ratio of 1.0 would have removed 1,816 mg chloroquine, only 18.2% of the amount ingested. This limited contribution of hemoperfusion to the total clearance makes it ineffective.

CONCLUSION

Hemoperfusion is not effective in severe chloroquine poisoning, even when started (relatively) early in the course of the intoxication. Toxicokinetic evaluation of a chloroquine poisoning should be based on the evaluation of plasma and whole blood concentrations.

Hydroxychloroquine retinopathy

We analyzed ocular findings from two patients (aged 49 and 60 years) with hydroxychloroquine (Plaquenil, Winthrop Pharmaceuticals, Division of Sterling Drug, Inc., New York, New York) retinopathy. Both patients were treated for systemic lupus erythematosus; one patient was treated with 400 to 800 mg of hydroxychloroquine per day (6.1 to 12.2 mg/kg of body weight/day) over a ten-year period. Cumulative doses were 1,788 and 2,920 g, respectively. Neither patient had ever been treated with chloroquine. One patient complained of glare and difficulty in adjusting to changes in illumination, whereas the other was asymptomatic. Both had bilateral visual acuities of 20/25, pericentral scotomata, and increased final dark-adapted rod thresholds in the two retinal areas that were tested. Fullfield electroretinograms were reduced and delayed, and focal cone electroretinography showed abnormal foveal responses as well. Ophthalmoscopy and fluorescein angiography showed a bull's-eye maculopathy in both eyes of one patient and perifoveal depigmentation in both eyes of the other patient. Retinal function remained stable at follow-up examinations 18 to 24 months after the cessation of hydroxychloroquine treatment. These two cases demonstrate that peripheral retinopathy, as well as maculopathy, can develop in patients who are treated with hydroxychloroquine for systemic lupus erythematosus, and that retinal function may remain stable after discontinuation of hydroxychloroquine treatment.

Photoaging/photodamage and photoprotection

Exposure to sunlight can produce both acute and long-term effects. Acute changes include erythema, photosensitivity, and immunologic alterations. Long-term consequences include carcinogenesis and photoaging. All effects can be minimized by photoprotection. This article reviews the adverse effects of sun exposure and strategies to reduce photodamage.

Survival after chloroquine ingestion in a child

We report the case of a 17 month old, 14 kg male who ingested 4 grams of chloroquine phosphate. He developed ventricular fibrillation and cardiovascular collapse 1 hour after the ingestion. After resuscitation he was treated with diazepam 2 mg/kg acutely, and 0.25 mg/kg/hour for 4 days with no further cardiac electrophysiologic abnormalities. Gallium-67 scan showed increased radionuclide uptake in heart and renal cortex, but there was no clinical evidence of myocardial or renal dysfunction at the time of the scan. He survived with severe neurologic sequelae from the cardiovascular collapse. He had dynamic peripheral neuropathy and progressive loss of retinal function, as evidence of ongoing chloroquine neurotoxicity.

Effect of chronic chloroquine treatment on prostaglandin and human chorionic gonadotropin (hCG) stimulation of testosterone secretion by the rat testis

The effect of chronic chloroquine administration on prostaglandin E1 (PGE1) and human chorionic gonadotropin (hCG) stimulation of testosterone secretion by the rat Leydig cells was studied. Adult albino (Wistar strain) rats were injected with 4 mg/kg body weight of chloroquine phosphate every other day for 30 days. At the end of the period of treatment, the rats were sacrificed and the Leydig cells incubated with hCG and/or PGE1 for 3 hrs. The amount of testosterone secreted was estimated by radioimmunoassay. Chronic chloroquine treatment did not affect the activity of the Leydig cells and combined PGE1 and hCG did not show any additive effects.

Chloroquine excretion following malaria prophylaxis

Urinary excretion of chloroquine and its desethyl-metabolite was monitored for up to 395 days after the last dose of oral chloroquine (300 mg base) taken once weekly for 10 weeks as malaria prophylaxis. Concentrations in plasma could be followed for up to 70 days after the last dose. A three exponential decay was applied to the urinary excretion data. The half-life of the terminal phase varied from 45 to 55 days for chloroquine and from 59 to 67 days for the metabolite. Mean residence time was approximately 20 days for the parent compound and 35 days for the metabolite, indicating that the terminal phases are of less importance for the effective half-lives.

Aspects of chloroquine mutagenicity

Using the Ames plate reversion and fluctuation tests, the mutagenic activity of chloroquine was tested in the new tester strains of Salmonella typhimurium, TA97, TA102, and Escherichia coli strains WP2, WP2hcr, WP6 and WP67. The E. coli transconjugants obtained from the mating transfer of R-plasmid(s) in strains TA97 and TA102 respectively to E. coli WP2, i.e. EE97 and EE102, were also tested. Chloroquine reverted strain TA97 from histidine dependence to independence and also reverted E. coli strains EE97 and EE102 from tryptophan dependence to independence. The E. coli strains WP2, WP2hcr; WP6 and WP67 and S. typhimurium TA102 were not affected. S. typhimurium TA97 could be reverted with 250 ng/ml of chloroquine (therapeutic blood level of chloroquine is 300 ng/ml). Reversion generally occurred optimally at the relatively lower concentrations of chloroquine i.e. 25, 50 micrograms/ml than at higher concentrations. From the properties of the reverted tester strains, the results indicated that chloroquine per se mediated frameshift reversion.

Deferoxamine (Desferal)-induced toxic retinal pigmentary degeneration and presumed optic neuropathy

Eight patients (16 eyes) developed ocular toxicity while undergoing intravenous deferoxamine mesylate (Desferal) chelation therapy for transfusional hemosiderosis. Presenting symptoms included decreased visual acuity, color vision abnormalities, and night blindness. Six patients presented as presumed retrobulbar optic neuropathy demonstrating central scotomas and color vision abnormalities. The remaining two patients presented with pigmentary changes confined either to the macula or equator. Following cessation of therapy, vision improved in all but four eyes, which did not attain their pretreatment visual acuity. Optic neuropathy resolved in all cases. However, follow-up revealed development of retinal pigmentary degeneration in seven patients, involving the macula in six and the equatorial retina in one. Fluorescein angiography and electrophysiological tests suggested toxicity at the level of retinal pigment epithelium and photoreceptors.

Animal toxicity and pharmacokinetics of hydroxychloroquine sulfate

Chloroquine is two to three times as toxic in animals as hydroxychloroquine, even though various single and repeated oral dosage regimens in man have given nearly identical plasma level curves. Tissue distributions are qualitatively similar for both drugs in albino rats--namely, bone, fat, and brain less than muscle less than eye less than heart less than kidney less than liver less than lung less than spleen less than adrenal--but the absolute distribution values are about 2.5 times higher for chloroquine. The metabolism of chloroquine and hydroxychloroquine differs only in that the latter drug gives two first-stage metabolites, whereas chloroquine gives one. Oral absorption of both drugs in man is nearly complete. However, three times as much chloroquine as hydroxychloroquine appears in the urine, and three times as much hydroxychloroquine as chloroquine appears in the feces.

Tissue and blood concentrations of chloroquine following chronic administration in the rat

The antimalarial drug, chloroquine, is extensively distributed in tissue and slowly eliminated such that after a single dose, a plasma half-life of 3-5 days has been found (McChesney & McAuliff 1961; McChesney et al 1967). A peak tissue/plasma concentration ratio greater than 300 is obtained in many tissues and after a single dose the drug can be found in the liver and urine for up to five years (Gaudette & Coatney 1961; Rubin et al 1963; Zvaifler et al 1963). Chronic administration of chloroquine for the treatment of rheumatoid arthritis has revealed an ocular toxicity due to accumulation of the drug in the pigmented layers of the eye, particularly the choroid (Fuld & Horwish 1958; Fuld 1959). A more recent indication for chronic administration of chloroquine is in the prophylaxis of malaria, for which the drug is administered at a dose of 300-600 mg weekly to adults. The long term toxic effects of chloroquine when administered in this way are unknown but no ocular toxicity has been reported even after five years of such use. Since tissue toxicity and other untoward effects are largely determined by tissue stores (Fuld & Horwish 1958; Fuld 1959) and blood levels (Laaksonen et al 1974; Frisk-Holmberg et al 1979) of the drug, it is useful to know the changes occurring in tissue and plasma concentrations during chronic administration. Previous studies in animals have given conflicting results. McChesney et al (1965) found a steady increase in the tissue and plasma concentrations in rats throughout a 3-month period although the increase was fastest in the first month. Grundmann et al (1972) found that most rat tissues were saturated with chloroquine between the 10th and the 16th weeks. Plasma concentrations were not measured hence the effect of tissue saturation on blood levels was not determined, yet saturation of tissue stores would be expected to lead to a rapid increase in plasma concentration that could affect the pattern and incidence of adverse reactions to the drug. We have reinvestigated the uptake of chloroquine by rat tissues during chronic administration of the drug and in particular to relate the tissue levels to plasma concentrations.

Sunscreens: topical and systemic approaches for protection of human skin against harmful effects of solar radiation

This review deals with topical and systemic approaches for protection of human skin against the harmful effects of solar radiation. Two concerns about the deleterious effects of sun exposure involve: (1) acute effects (e.g., sunburn and drug-induced phototoxicity) and (2) potential long-term risks of repeated sun exposures leading to development of solar elastosis, keratoses, induction of both nonmelanoma and melanoma skin cancer, and alteration of immune responses and functions. Action spectra of normal and abnormal reactions of human skin to acute and chronic effects of solar radiation are presented with a view to helping the physician prescribe the appropriate sunscreens. Factors that influence acute effects of sunburn are reviewed. Various artificial methods effective in minimizing or preventing harmful effects of solar radiation, both in normal individuals and in patients with photosensitivity-related problems, are discussed. Emphasis is placed on the commercially available chemical sunscreens and their properties. Sun protection factor (SPF) values of several brand-name formulations determined with a solar simulator under indoor conditions (laboratory) and with solar radiation under natural, field conditions are presented. Factors responsible for variations of SPF values observed under indoor and outdoor conditions are reviewed. Systemic photoprotective agents and their limitations are outlined. The photobiology of melanin pigmentation (the tanning reaction) is briefly discussed, with emphasis on the dangers of using quick-tanning lotions for stimulation of the tanning reaction.

Chloroquine retinopathy: is there a safe daily dose?

Published case reports of chloroquine retinopathy rarely include details of daily dosage, but 30 reports where this information was available included 78 patients who developed impaired visual acuity an 13 had received daily doses of 250 mg or less. Eleven cases of ocular toxicity attributed to chloroquine were reported to the Committee on Safety of Medicines but only 2 developed impaired vision on 250 mg daily. A postal questionnaire among 41 rheumatology and 33 ophthalmology centres showed 2 patients who developed impaired vision as a result of treatment with chloroquine in a daily dose not exceeding 250 mg. Serious visual impairment related to chloroquine rarely occurs if the daily dose does not exceed 250 mg.

Antimalarials

The antimalarials, chloroquine, hydroxychloroquine, and quinacrine, are used primarily for malaria; but they can be beneficial for cutaneous lupus erythematosus (LE), polymorphous light eruption, solar urticaria, and porphyria cutanea tarda. Antimalarials bind to deoxyribonucleic acid (DNA) which prevents DNA and ribonucleic acid (RNA) polymerase reactions and DNA heat inactivation; and they inhibit the LE cell phenomenon, antinuclear antibody reactions, and suppress lymphocyte transformation. By competing with calcium ion, they stabilize membranes and have an anesthetic effect. Their anti-inflammatory potential is due to their inhibition of hydrolytic enzymes, stabilization of lysosomes, interference with prostaglandin synthesis, blocking of chemotaxis, and antagonism of histamine responses. The antimalarials have no sunscreening properties. The most common toxic effects are cutaneous pigmentation, nausea, vomiting, diarrhea, mild ileus, and cycloplegia. There has been a reluctance to use chloroquine and hydroxychloroquine because of the possibility of retinopathy. However, if the "safe" daily dose limit of chloroquine, 2 mg per pound of body weight, and of hydroxychloroquine, 3.5 mg per pound of body weight, is followed, the chance of retinopathy is slight. Quinacrine does not cause retinopathy, but it has more cutaneous side effects than the other two agents.

Retinopathy after tilorone hydrochloride

Two patients, a 34-year-old woman and a 50-year-old woman, received tilorone HCl, an experimental antitumor drug. After taking the drug orally (total dose, 152 g), the first patient developed corneal subepithelial infiltrates and toxic retinopathy characterized by fine pigment mottling of the peripheral fundus and macula with mild arteriolar narrowing. Although visual acuity was 6/6 (20/20) throughout treatment, Goldmann perimetry showed marked peripheral constriction of the visual fields and results of an electroretinogram and an electro-oculogram were abnormal. After taking the drug orally (total dose, 189 g), the second patient developed corneal subepithelial infiltrates, severe bilateral arteriolar narrowing, and mild pigment mottling of the macula. ERG and EOG were moderately attenuated. Visual fields by Goldman perimetry were within normal limits. Tilorone HCl, like chloroquine, may be an antioxidant that affects the free radical scavenging mechanism of the retinal pigment epithelium. Extensive testing should be done on all patients taking tilorone HCl in order to detect the initial manifestations of retinopathy.

The uptake of 14C-chloroquine by mouse pancreatic islets in vitro

The uptake of 14C-chloroquine by isolated mouse pancreatic islets in vitro was investigated. The islets were found to have a very high capacity to accumulate the substance. The uptake of 14C-chloroquine in the islets was a saturable process. Metabolic inhibitors, ouabain, anaerobic conditions and absence of glucose did not inhibit the uptake of 14C-chloroquine in the islets, suggesting that the substance is accumulated by some means other than energy-dependent active transport or pinocytosis. The uptake of 14C-chloroquine was inhibited by low temperature and low pH and in the presence of mepacrine, chlorpromazine, imipramine and desmethylimipramine. Only a small part of the 14C-chloroquine which had been taken up in the islets left the cells during 45 min. incubation in non-radioactive media. Two possible mechanisms for the uptake of 14C-chloroquine in the islets are considered: (1) The accumulation may be due to a binding of the substance to cellular constituents. (2) Chloroquine may be trapped by protonation within lysosomes or other membrane-surrounded organelles with low pH.

Mutagenicity evaluation of the two antimalarial agents chloroquine and mefloquine, using a bacterial fluctuation test

The two antimalarial agents chloroquine and mefloquine have been tested for mutagenicity in Salmonella typhimurium strains TA1535, TA1537 and TA1538. Chloroquine was found to revert strain TA1537 at concentrations of 100 and 250 micrograms/ml, most likely due to intercalation. No mutagenicity was found with mefloquine at concentrations up to 2.5 micrograms/ml, neither without nor with metabolic activation by Ca2+-precipitated rat liver microsomes. Higher concentrations of mefloquine and chloroquine inactivated the bacteria.

Nonfatal chloroquine poisoning

Acute overdosage with chloroquine is a life-threatening emergency. Adults who have ingested greater than 3 gm of chloroquine phosphate have died within 2 hr after ingestion. We describe the rapid onset of typical gastrointestinal, central nervous system, respiratory, and cardiovascular symptomatology in a 49-year-old female who ingested 19.5 gm of chloroquine phosphate. Prompt emesis, lavage, administration of activated charcoal, and aggressive treatment of hypotension and respiratory distress were responsible for the patient's recovery within 6 hr.

Peripheral visual field restriction in chloroquine retinopathy. Report of a case

Chloroquine compounds are known to cause a retinopathy which typically begins in the central fundus giving rise to a "bull's eye" macula. Ultimately peripheral changes may become apparent. In the routine eye examination of such patients emphasis has been laid on the central area of the fundus. A case is presented where the retinopathy was not diagnosed until marked peripheral changes had occurred with peripheral pigment changes, attenuated retinal vessels, slight optic atrophy, peripheral visual field restriction and a subnormal electroretinogram. The typical "bull's eye" changes were not apparent. Routine examination of the peripheral fundus by means of ophthalmoscopy and perimetry is necessary to avoid missing any such retinopathy.