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PubMed2002

Synthesis and antimalarial activity of some new 1,2-dioxolane derivatives.

The synthesis of 1,2-dioxolane derivatives in two different acetophenone series, as simplified models of natural coumarins is described. 2-Acetyl-3-acetoxy-4-(3-hydroperoxy-3-methylbut-1-enyl)phenyl acetate and 2-acetyl-5-acetoxy4-(3-hydroperoxy-3-methylbut-1-enyl) phenyl acetate synthons are used as precursors to these structures. In vitro antimalarial activity of the 1,2-dioxolane derivatives has been investigated.

Acetophenones↗
PubMed2000

Interaction of antimalarial agent artemisinin with cyclodextrins.

To obtain an effective solution of the poorly water soluble antimalarial agent artemisinin, the use of several kinds of cyclodextrins (CDs) as solubilizers was examined. The following CDs were used in this study: alpha-CD, beta-CD, gamma-CD as parent CDs, 2-hydroxypropyl-beta-CD (HP-beta-CD), sulfobutyl ether beta-CD (SBE7-beta-CD), heptakis (2,6-di-O-methyl)-beta-CD (DM-beta-CD), 2,3,6-partially methylated-beta-CD (PM-beta-CD) as modified CDs, and glucosyl-beta-CD (G1-beta-CD), and maltosyl-beta-CD (G2-beta-CD) as branched CDs. The solubility curves of artemisinin with CDs can all be classified as type AL. The apparent stability constants for artemisinin-parent CD complexes increased in the order of alpha- < gamma- < or = beta-CD. The constants for artemisinin-beta-CD derivative (and beta-CD) complexes increased in the order of G2-beta-CD approximately equal to G1-beta-CD approximately equal to PM-beta-CD approximately equal to beta-CD < HP-beta-CD < SBE7-beta-CD < DM-beta-CD. These results suggest that the addition of CDs enables the solubilization of artemisinin.

Antimalarials↗
PubMed2000

The mechanisms of parasite clearance after antimalarial treatment of Plasmodium falciparum malaria.

Studies were conducted to determine how malaria parasites are cleared from the blood after antimalarial treatment. Neither artesunate nor quinine decreased parasitized red cell deformability or increased antibody binding. In acute falciparum malaria, ring-infected erythrocyte surface antigen (RESA) was observed in erythrocytes without malaria parasites (RESA-red blood cell [RBC]), indicating prior parasitization. In uncomplicated malaria, RESA-RBC numbers increased significantly (P=.002) within 24 h of starting artesunate but rose much more slowly (7 days) after quinine treatment. In severe malaria, RESA-RBC increased significantly (P=. 001) within hours of starting artesunate but not with quinine treatment (P=.43). RESA-RBCs were not produced after drug treatment of malaria parasite cultures in vitro. Rapid malaria parasite clearance after treatment with artemisinin derivatives results mainly from the extraction of drug-affected parasites from host erythrocytes-presumably by the spleen. This explains why the fall in hematocrit after treatment of hyperparasitemia is often less than that predicted from loss of parasitized cells.

Animals↗
PubMed2003

Stevens-Johnson syndrome associated with Malarone antimalarial prophylaxis.

To the best of our knowledge, Stevens-Johnson syndrome (SJS) has not been reported previously as an adverse reaction to Malarone, which is a combination of atovaquone and proguanil hydrochloride used for antimalarial prophylaxis and therapy. We describe a 65-year-old patient who had SJS with typical clinical and histopathological findings associated with the use of Malarone prophylaxis for malaria. This report should alert physicians to this severe cutaneous reaction, and Malarone should be added to the list of drugs that can potentially cause SJS.

Aged↗
PubMed2004

Antiretrovirals as antimalarial agents.

Recent studies have indicated that antiretroviral protease inhibitors may affect outcome in malarial disease. We have investigated the antimalarial activities of 6 commonly used antiretroviral agents. Our data indicate that, in addition to the previously published effects on cytoadherence and phagocytosis, the human immunodeficiency virus (HIV)-1 protease inhibitors saquinavir, ritonavir, and indinavir directly inhibit the growth of Plasmodium falciparum in vitro at clinically relevant concentrations. These findings are particularly important in light of both the high rate of malaria and HIV-1 coinfection in sub-Saharan Africa and the effort to employ highly active antiretroviral therapy in these regions.

Animals↗
PubMed2006

Complexity of Plasmodium falciparum infections and antimalarial drug efficacy at 7 sites in Uganda.

Malaria infections in Africa frequently include multiple parasite strains. We examined the relationship between the number of infecting Plasmodium falciparum strains and the responses to 3 different combination therapies in 3072 patients with uncomplicated malaria at 7 sites in Uganda. Patients infected with > or =3 strains had almost 3 times the odds of treatment failure (odds ratio, 2.93 [95% confidence interval, 2.51-3.43]; P<.001), compared with those infected with 1 or 2 strains. Our data suggest that efforts to reduce the complexity of infection in highly endemic areas through the use of intermittent presumptive therapy, improved case management, and reduction in transmission intensity may improve the efficacy of antimalarial therapies.

Adolescent↗
PubMed2006

HIV-1 immune suppression and antimalarial treatment outcome in Zambian adults with uncomplicated malaria.

BACKGROUND: Human immunodeficiency virus (HIV)-1 infected adults with low CD4 cell count have a higher risk of malaria infection and clinical malaria. We assessed the influence that HIV-1 immune suppression has on the efficacy of antimalarial treatment in adults with uncomplicated malaria. METHODS: This clinical trial included 971 Zambian adults with uncomplicated malaria. Patients were tested for HIV-1, and, if positive, a CD4 cell count was assessed. The primary outcome was recurrent parasitemia corrected by molecular genotyping within 45 days after treatment. RESULTS: HIV-1 infection was detected in 33% (320/971) of adult patients with malaria. Treatment failure was not associated with HIV-1 infection (relative risk [RR], 1.12 [95% confidence interval {CI}, 0.82-1.53]; P=.45). HIV-1-infected patients with a CD4 cell count <300 cells/microL had an increased risk of recurrent parasitemia, compared with those with a CD4 cell count >or=300 cells/microL (RR, 2.24 [95% CI, 1.20-4.14]; P=.01). After genotyping, the risk of recrudescence was higher in HIV-1-infected patients with a CD4 cell count <300 cells/microL than in the other patients with malaria (RR, 1.67 [95% CI, 1.13-2.47]; P=.02). CONCLUSION: HIV-1-infected patients with malaria with a CD4 cell count <300 cells/microL have a higher risk of experiencing a recrudescent infection, compared with those with a CD4 cell count >or=300 cells/microL or without HIV-1 infection. Trial registered at http://www.clinicaltrials.gov/; reference number NCT00304980.

Adolescent↗
PubMed1997

Safety and immunogenicity of live oral cholera and typhoid vaccines administered alone or in combination with antimalarial drugs, oral polio vaccine, or yellow fever vaccine.

The effects of concomitant administration of antimalarial drugs, oral polio vaccine, or yellow fever vaccine on the immune response elicited by the Vibrio cholerae CVD103-HgR and Salmonella typhi Ty21a live oral vaccines were investigated. Healthy adults were immunized with CVD103-HgR alone or combined with Ty21a. Subjects were randomized to simultaneously receive mefloquine, chloroquine or proguanil, or oral polio or yellow fever vaccine. The vibriocidal antibody seroconversion rate was significantly reduced (P = .008) only in the group that received chloroquine with the CVD103-HgR. The geometric mean vibriocidal antibody titer was significantly decreased in the groups that received chloroquine (P = .001) or mefloquine (P = .02) compared with titers in groups that received CVD103-HgR alone. However, similar immunosuppressive effects were not observed in the groups immunized with Ty21a and CVD103-HgR. Only the concomitant administration of proguanil effected a significant (P = .013) decline in the anti-S. typhi lipopolysaccharide antibody response. These results indicate that chloroquine and proguanil should not be simultaneously administered with the CVD103-HgR and Ty21a vaccine strains, respectively.

Administration, Oral↗
PubMed2005

Short-term effects of vitamin A and antimalarial treatment on erythropoiesis in severely anemic Zanzibari preschool children.

BACKGROUND: The pathophysiology of anemia in coastal East Africa is complex. Impaired erythropoietin production is one possible mechanism. Plasmodium falciparum malaria has been found to blunt erythropoietin production, whereas vitamin A stimulates erythropoietin production in vitro. OBJECTIVE: We investigated the 72-h effects of vitamin A and the antimalarial drug sulfadoxine pyramethamine (SP) on erythropoietin production in severely anemic (hemoglobin < or = 70 g/L) preschool children in Zanzibar, a region of known vitamin A deficiency. We hypothesized that both treatments would stimulate erythropoietin production directly, within 72 h, before a change in hemoglobin would occur. DESIGN: One hundred forty-one severely anemic children were identified during the baseline assessment of a morbidity substudy of a community-based micronutrient supplementation trial. All severely anemic children were randomly assigned to receive either vitamin A (100,000 or 200,000 IU depending on age) or SP at baseline; 72 h later they received the opposite treatment plus daily hematinic syrup for 90 d. Erythropoietic and parasitic indicators were assessed at baseline and again after 72 h. RESULTS: After 72 h, SP reduced the malaria parasite density (by 5029 parasites/microL; P < 0.001), CRP concentrations (by 10.6 mg/L; P = 0.001), and the proportion of children infected with malaria (by 32.4%; P < 0.001). Vitamin A reduced CRP (by 9.6 mg/L; P = 0.011), serum ferritin (by 18.1 microg/L; P = 0.042), and erythropoietin (by 194.7 mIU/mL; P = 0.011) concentrations and increased the reticulocyte production index (by 0.40; P = 0.041). CONCLUSIONS: Contrary to our hypothesis, vitamin A significantly decreased erythropoietin concentration. The most important effect of both vitamin A and SP was the rapid reduction of inflammation. Vitamin A also mobilized iron from stores and stimulated the production of new erythrocytes.

Anemia↗
PubMed1996

Antimalarial drugs reduce cytoadherence and rosetting Plasmodium falciparum.

The in vivo and in vitro effects of antimalarials on cytoadherence and rosette formation were studied in 17 patients with severe and 46 with uncomplicated falciparum malaria. Cytoadherence was increased in severe malaria (P<.001). Artesunate and artemether were more potent than quinine in inhibiting both adherence properties. Artesunate was the most rapidly acting drug tested, producing >50% inhibition of both cytoadherence and rosetting in vivo and in vitro within 2 hr of drug exposure. Exposure to quinine for > or = to 4 h in vivo reduced rosetting by >50%, but not cytoadherence. Quinine did not reduce cytoadherence or rosetting significantly in vitro with exposure times of < or = to 8 h. These results suggest that artemisinin derivatives are more effective than quinine in preventing pathologic processes in parasitized erythrocytes that contribute to microvascular obstruction in severe malaria.

Adolescent↗
PubMed2000

Simple 1,2-aminoalcohols as strain-specific antimalarial agents.

We report here the in vitro activity of a selection of 1, 2-aminoalcohol-containing compounds against cloned strains of human Plasmodium falciparum. These compounds exhibit moderate antimalarial activity but a high degree of strain specificity, preferentially inhibiting a chloroquine-resistant strain of the organism.

Animals↗
PubMed2002

Two novel assays for the detection of haemin-binding properties of antimalarials evaluated with compounds isolated from medicinal plants.

Forty-two compounds isolated from nine plants used within South America for the treatment of malaria were tested for haemin binding using two novel, rapid screening methods. The data obtained were analysed with respect to IC(50) values for in vitro toxicity to Plasmodium falciparum trophozoites. One method, a multiwell assay based on the inhibition of the interaction of haemin with glutathione (GSH), is sensitive in the 10 microM range, takes c. 1 h and is suitable for either a high throughput screen or rapid assay during natural product isolation. Of 19 compounds showing antiplasmodial activity (IC(50) < 40 microM), 16 (84%) showed >40% inhibition of GSH-haemin reaction. The sensitivity and specificity of the assay were 0.85 and 0.82, respectively. The positive predictive value was 0.81 and the negative predictive value 0.86. A more sensitive assay (0.1 microM range) is based on the reversal by haemin-binding compounds of the haemin inhibition of the L-dopachrome-methyl ester tautomerase activity of human macrophage migration inhibitory factor. This assay gives a better idea of the affinity of interaction and uses very small amounts of test compound. The log[RI(50)] of eight of the compounds that tested positive in the above assays together with those of quinine and chloroquine showed a positive correlation with log[antiplasmodial IC(50)] for strain T9-96 (r = 0.824) and strain K1 (r = 0.904). Several of the antimalarial compounds that bind haemin are isoquinolines, a class not shown previously to interact with haemin.

Animals↗
PubMed1995

Incidence of myopathy in patients treated with antimalarials. A report of three cases and a review of the literature.

A retrospective review of 4405 patients' charts identified 214 patients who initiated antimalarial therapy between January 1987 and April 1993 for different rheumatic disorders (mean duration of therapy of 17 months). From these, three patients with myopathy were found for a total of 303 patient-years of therapy, for an incidence of 1 in 100 patient-years (95%, confidence interval 0.2-3). All three patients had rheumatoid arthritis and had received chloroquine for between 12 and 18 months with a maximum dose of 250 mg/daily. All had a muscle biopsy, but only one showed the classical rimmed vacuoles. All patients improved within 2 months after the drug was stopped. A review of the literature was carried out with special reference to the significance of clinical myopathy with a negative biopsy. We found that positive biopsies are usual only if the duration of symptoms have been allowed to persist for more than 6 months.

Adult↗
PubMed1991

Disease-modifying antirheumatic drugs: gold, penicillamine, antimalarials, and sulfasalazine.

In the assessment of the effects of disease-modifying antirheumatic drugs, three or four clinical measurements supported by the erythrocyte sedimentation rate, and sometimes radiographs, are generally agreed to be correct. Some advocate functional assessments also, or even alternatively. Several studies compared gold, penicillamine, antimalarials, and sulfasalazine either with each other or with placebo, and occasionally with methotrexate. No important differences between the general performance of the four drugs were found. More work was reported on sulfasalazine than on the other three drugs; the data support that it has a place in our armamentarium. Several important contributions concerned strategies of treatment. It is considered that disease-modifying antirheumatic drugs should be used earlier and more aggressively in rheumatoid arthritis. This aspect was perhaps the key note of the 1990 literature on this topic. As part of the new strategies, combination therapy is urged by some rheumatologists, whereas others urge caution on the grounds that we do not yet know enough about the effects of combinations, or by how much the risks of adverse effects are increased in combination.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Detection and prevention of maculopathy associated with antimalarial agents.

Rheumatologists use both cholorquine and hydroxychloroquine in the treatment of systemic arthritic and immune disease. Hydroxychloroquine is much more expensive but is better tolerated by patients. My experience in watching patients being switched from one drug to another suggests that chloroquine is more effective in some patients than is hydroxychloroquine. Reynes thought that a review of the literature suggests that chloroquine is more toxic at 250 mg/day as compared to 400 mg of hydroxychloroquine if dose is based on these dosages. This theory may be related, in part, to the observation by Raines and associates that chloroquine crosses the blood-retinal barrier whereas hydroxychloroquine does not. Patients should be assessed 6 months after starting antimalarials. Routine automated perimetry is not indicated. An appropriate examination would include visual acuity testing, color-vision testing, Amsler grid testing, and corneal assessment. Patients should be dosed on the basis of ideal body weight (not actual body weight) to reduce the incidence of macular toxicity. Patients with no risk factors should be examined no more than once a year.

Antimalarials↗
PubMed2006

Three 4-aminoquinolines of antimalarial interest.

The structures of three compounds with potential antimalarial activity are reported. In N,N-diethyl-N'-(7-iodoquinolin-4-yl)ethane-1,2-diamine, C15H20IN3, (I), the molecules are linked into ribbons by N-H...N and C-H...N hydrogen bonds. In N-(7-bromoquinolin-4-yl)-N',N'-diethylethane-1,2-diamine dihydrate, C15H20BrN3.2H2O, (II), two aminoquinoline molecules and four water molecules form an R5(4)(13) hydrogen-bonded ring which links to its neighbours to form a T5(2) one-dimensional infinite tape with pendant hydrogen bonds to the aminoquinolines. The phosphate salt 7-chloro-4-[2-(diethylammonio)ethylamino]quinolinium bis(dihydrogenphosphate) phosphoric acid, C15H22ClN3(2+).2H2PO4-.H3PO4, (III), was prepared in order to establish the protonation sites of these compounds. The phosphate ions form a two-dimensional hydrogen-bonded sheet, while the aminoquinoline cations are linked to the phosphates by N-H...O hydrogen bonds from each of their three N atoms. While the conformation of the quinoline region hardly varies between (I), (II) and (III), the amino side chain is much more flexible and adopts a significantly different conformation in each case. Aromatic pi-pi stacking interactions are the only supramolecular interactions seen in all three structures.

Aminoquinolines↗
PubMed1988

Redetermination of the crystal and molecular structure of the antimalarial chloroquine bis(dihydrogenphosphate) dihydrate.

N4-(7-Chloro-4-quinolinyl)-N',N'-diethyl-1,4-pentanediamine bis(dihydrogenphosphate) dihydrate, C18H28ClN2+(3).2H2PO-4-2H2O, Mr = 551.8, monoclinic, P2(1)/c, a = 9.830 (2), b = 16.879 (3), c = 15.783 (4) A, beta = 105.51 (2) degrees, V = 2523.2 A3, Z = 4, Dx = 1.452 g cm-3, Mo K alpha, lambda = 0.71073 A, mu = 2.78 cm-1, F(000) = 1168, room temperature, final R = 5.5% for 2431 reflections with [F0] greater than 3 sigma. The chloroquine molecule is a dication with a hydrogen atom from each of the phosphate moieties residing on the quinoline and the terminal chain nitrogen atoms. Neighboring phosphate chains are bridged by chloroquine molecules via hydrogen bonding. Each hydrogen atom on each nitrogen atom, on each phosphate oxygen atom, and in each water molecule participates in hydrogen bonding. The helical manner in which the side chains of the chloroquine molecules wrap around phosphate chains and the stacking interval of the quinoline rings between the phosphate groups may be indicative of the interaction of chloroquine molecules with cellular constituents important to antimalarial action.

Antimalarials↗
PubMed2005

Semi-mechanistic pharmacokinetic/pharmacodynamic modelling of the antimalarial effect of artemisinin.

PURPOSE: To characterize artemisinin pharmacokinetics (PK) and its antimalarial activity in vivo. METHODS: Artemisinin salivary concentration and parasite count data were obtained from Vietnamese malaria patients receiving two different dosage regimens. PK data were analysed using a previously developed semiphysiological model incorporating autoinduction of eliminating enzymes. A pharmacodynamic (PD) model reflecting different stages of the parasite life-cycle was developed and fitted to the data. The model included visible and invisible compartments as well as sensitive, insensitive, and injured parasite stages. Salivary artemisinin concentrations functioned as the driving force for the observed decrease in the number of parasites. RESULTS: Large interindividual variability was observed in both PK and PD data. The PK model described reasonably well the observed decrease in salivary concentrations after repeated drug administration. The preinduction hepatic extraction ratio of artemisinin was estimated to be 0.87 with a volume of distribution of 27 L. Artemisinin half-life averaged 0.7 h. Incorporation of a saturable hepatic elimination affecting the first-pass extraction as well as a higher intrinsic clearance in female patients resulted in the best fit of the model to the data. The PD model described the decrease in the number of parasites during the course of treatment well. The longest mean transit time of parasites from sensitive, visible to invisible to insensitive visible stages was found to be 34.5 h through one life-cycle. The half-life of injured parasites was 2.7 h. CONCLUSIONS: The proposed semimechanistic PK/PD model successfully described the time course of both salivary artemisinin concentrations after repeated dosing and the number of parasites in patients treated with the drug.

Antimalarials↗