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Improved targeting of antimony to the bone marrow of dogs using liposomes of reduced size.

A novel liposomal formulation of meglumine antimoniate (MA), consisting of vesicles of reduced size, has been evaluated in dogs with visceral leishmaniasis to determine its pharmacokinetics as well as the impact of vesicle size on the targeting of antimony to the bone marrow. Encapsulation of MA in liposomes was achieved through freeze-drying of empty liposomes in the presence of sucrose and rehydration with a solution of MA. The resulting formulation, with a mean vesicle diameter of about 400 nm, was given to mongrel dogs with visceral leishmaniasis as an i.v. bolus injection at 4.2 mgSb/kg of body weight. The pharmacokinetics of antimony were assessed in the blood and in organs of the mononuclear phagocyte system and compared to those achieved with the free drug and the drug encapsulated in large sized liposomes (mean diameter of 1200 nm). The targeting of antimony to the bone marrow was improved (approximately three-fold) with the novel liposomal formulation, when compared to the formulation of MA in large sized liposomes. This study provides the first direct experimental evidence that passive targeting of liposomes to the bone marrow of dogs is improved by the reduction of vesicle size from the micron to the nanometer scale.

Animals↗

[Liposomal amphotericin B in secondary prophylaxis of visceral leishmaniasis in HIV-infected patients: report of five clinical cases].

Treatment of visceral leishmaniasis in HIV patients encounters inefficacy and relapse due to drug resistance, toxicity and immunodepression. Our goal was to evaluate treatment of these patients by liposomal amphotericin B (L-AmB). Since 1998, five clinical files were exploitable out of 13 patients. Protocols used bolus doses ranging between 2.9 and 4.1 mg/kg dispatched on 5-24 days, followed by maintenance dose ranging from 2.7 to 3.8 mg/kg every 15 days. Attack treatment involved high bolus dose (cumulated doses ranging from 60 to 86 mg/kg at day 30) and allowed favorable clinical and biological results with healing in four patients. Secondary prophylaxis with L-AmB has been efficacious and well tolerated in three patients. Although literature and study results cannot indicate a standard therapeutic care in these patients, an initial treatment by L-AmB at doses higher than marketing-approved doses with a secondary prophylaxis by L-AmB associated with an antiretroviral treatment seem to be major asset in order to obtain healing. Expanding this study to a multicenter trial should allow to better define the frequency and duration of the secondary prophylaxis and to evaluate the risk of therapeutic escape as well as the life-span increase.

Adult↗

Evaluation of renal and hepatic functions in dogs naturally infected by visceral leishmaniasis submitted to treatment with meglumine antimoniate.

The present study aimed to evaluate the renal and hepatic responses in eight dogs with visceral leishmaniasis submitted to treatment with meglumine antimoniate and to verify the occurrence of possible side effects. Urinalysis, hepatic and renal function tests were carried out in all animals at up to seven moments. After the end of a six-month observation period, all dogs were euthanized. Before the beginning of the experiment urinary and biochemical alterations were observed in four dogs due to the changes caused by the parasite itself. These alterations included the presence of renal cells, cylindruria, proteinuria, azotemia, hyperproteinemia and hypoalbuminemia. One dog died on the third day after treatment because an aggravation of the clinical picture, probably due to the medication. During the course of the study, an increase in hepatic enzymes was verified in two animals. Sixty days after the beginning of the treatment four dogs showed remission of clinical signs. The other three were asymptomatic with persistent biochemical alterations. From these, two presented recurrence of clinical signs about 150 days after the beginning of the treatment while in the other, hyperproteinemia persisted. Meglumine antimoniate was not efficient to treat dogs with severe renal dysfunction and the side effects observed were pain at the site of injection and the probable transient hepatotoxicity, evidenced by biochemical examinations, but without the presence of clinical signs.

Animals↗

Clinical and parasitological evaluation of dogs naturally infected by Leishmania (Leishmania) chagasi submitted to treatment with meglumine antimoniate.

Aiming to evaluate the efficacy of the treatment of canine visceral leishmaniasis, to verify the occurrence of a possible disease relapse, and to search for the presence of the parasites after the end of the treatment, seven dogs naturally infected by Leishmania (Leishmania) chagasi were used. The dogs were subjected to a treatment with 75 mg/kg meglumine antimoniate subcutaneously every 12 h for 21 days, and followed-up for a period of 6 months. During the whole experimental period the animals wore deltamethrin collars and were kept in a screened kennel to avoid reinfection. Lymph node and bone marrow aspiration biopsy was carried out to search for the parasite at seven moments: before the treatment, 30, 60, 90, 120, 150 and 180 days after the start of the treatment. After the end of the experiment all dogs were humanely euthanized. Then, spleen and liver "imprints" and in vitro cultures were carried out to search for amastigote forms of the parasite. During the treatment all animals presented remission of symptoms. However, two dogs were observed to present new symptoms in the course of the experiment. At the end of the experiment, the presence of amastigote forms of the parasite was evidenced in five of the seven dogs. This enabled us to conclude that the treatment promoted clinical cure but did not eliminate the parasites completely.

Animals↗

Characterization of circulating lymphocyte subpopulations in canine leishmaniasis throughout treatment with antimonials and allopurinol.

Canine leishmaniasis (CL) is a systemic parasitic disease with a wide variability of response to specific therapy: the majority of patients apparently improve with treatment, some of them respond but later relapse, and few of them do not respond at all. It has been demonstrated that the immune response plays a key role in the development and outcome of Leishmania infection in the dog and in the response to the treatment, although this response is not well understood. Some authors have suggested that ill dogs show a reduction in the percentage of circulating CD4+ lymphocytes and in the CD4+/CD8+ ratio, both of which normalize after treatment and clinical recovery. The present paper discusses the variation of the different lymphocyte subpopulations (CD3, CD4, CD8, CD21) of peripheral blood mononuclear cells (PBMC) in 28 dogs diagnosed with CL and submitted to conventional treatment with meglumine antimoniate (Glucantime) for 1 month and with allopurinol (Zyloric) for 1 year, in order to evaluate the usefulness of these parameters as indicators of the immunological condition of the ill animals and of the prognosis of their evolution during the treatment. It is concluded that circulating lymphocyte subpopulations are similar in dogs with leishmaniasis and in healthy dogs and that there is no correlation between the clinical status or response to therapy and the values of the counts of the different lymphocyte subpopulations. Therefore, the percentage of different lymphocyte subpopulations cannot be used as a parameter to predict the evolution of an individual patient in a clinical context.

Allopurinol↗

Inter-current and nosocomial infections among visceral leishmaniasis patients in Ethiopia: an observational study.

From July 1989 up to September 1997, a total of 247 non-HIV associated visceral leishmaniasis (VL) patients were treated on outpatient basis in rural clinics (195 patients) and hospitalised in the Northern-Omo Regional Hospital (18 patients) and in Addis Ababa referral hospitals (34 patients). Patients treated in the rural clinics and in the Regional hospital originated from the same endemic area and had comparable baseline characteristics. Overall rates of complications (inter-current/concurrent infectious or non-infectious diseases or deaths) in the three categories were 10.7, 38.9 and 61.6%, while case fatality rates were 2.5, 5.6 and 11.7%, respectively. Nosocomial bacterial infections occurred in 16.6% of patients treated in the Regional hospital and 32.3% of patients treated in Addis Ababa referral hospitals, and these infections accounted for 42.8 and 52.4% of the complications seen in the respective categories. Among VL patients originating from the same endemic place and with comparable baseline clinical data, patients treated hospitalised had significantly higher rates of complications than patients treated on outpatient basis (P<0.001). Patients who had complications during the course of VL therapy had significantly lower pre-treatment haemoglobin levels. Considering the extra cost of hospitalisation and risk of nosocomial infections and petavalent antimonial therapy being fairly safe, we recommend that VL patients, unless with serious complications, should preferably be treated on ambulatory basis with follow-up to monitor response and inter-current infections if any.

Adolescent↗

Human cutaneous leishmaniasis due to Leishmania infantum in the Sidi Bourouis focus (Northern Tunisia): epidemiological study and isoenzymatic characterization of the parasites.

The authors report an increase of the number of case of cutaneous leishmaniasis in the Sidi Bourouis region community of Siliana Governorate (Tunisia), with 38 cases diagnosed in 6 months (1st November 2000-30th April 2001), contrary to its usual sporadic character. The isoenzymatic identification of 15 isolated strains emphasizes the role of the Leishmania infantum zymodeme MON-1 as an important factor in the genesis of the sporadic cutaneous leishmaniasis of Northern Tunisia. In fact it was isolated in 6 cases while L. infantum MON-24, the usual agent was isolated in 9 cases.

Aged↗

Involvement of thiol metabolism in resistance to glucantime in Leishmania tropica.

Clinical resistance to pentavalent antimonials, in the form of pentostam (sodium stibogluconate) or glucantime (N-methylglucamine antimoniate), has long been recognized as a problem in Leishmaniasis. However, the mechanisms of resistance are unclear. We selected in vitro a Leishmania tropica line resistant to 1.2 mg/mL of Sb(V) of glucantime (GLU-R10). The cell line has a stable phenotype for at least 6 months and a resistance index of 1400-fold. The resistant line has no cross-resistance to pentostam or to SbCl3 and SbCl5. The resistance to glucantime was reverted by buthionine sulfoximine (BSO) and chlorambucil (CLB); however, thiol analyses by HPLC of wild-type and GLU-R10 cell lines, in the presence or absence of the drug, showed no differences between these two cell lines. The resistant line had a DNA amplification shown as a circular extrachromosomal element (G-circle) of approximately 22 kb. However, the specific probes for gamma-glutamyl cysteine synthetase, ornithine decarboxylase and trypanothione reductase did not recognize the G-circle amplified in the GLU-R10. The G-circle did not arise from the H region and was not related with P-glycoprotein Pgp-MDR- or Pgp-MRP-like genes. Northern blot analysis of the G-circle showed that a single transcript of approximately 6 kb was overexpressed in the resistant line. Molecular characterization of the G-circle would lead to the determination of the gene(s) involved in resistance to glucantime in Leishmania.

Animals↗

Pentavalent antimonial-induced torsade de pointes.

Unexplained sudden deaths following use of pentavalent antimonial drugs have been described, presumably owing to ventricular arrhythmias. A patient is reported with QT interval prolongation and syncopal episodes related to torsade de pointes following treatment of visceral leishmaniasis with meglumine antimoniate. This is the first reported case of documented torsade de pointes following treatment with pentavalent antimonial drugs.

Aged↗

Glucantime dosage.

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Antiprotozoal Agents↗