A. J. Baillie

Non‐ionic surfactant vesicles, niosomes, as a delivery system for the anti‐leishmanial drug, sodium stibogluconate

Liver and serum concentrations of antimony in the mouse have been determined after administration of sodium stibogluconate in the free, liposomal and niosomal form. High liver and low serum values were attained by the use of both vesicular formulations. Niosomal sodium stibogluconate was shown to be more active than free drug against experimental murine visceral leishmaniasis, an effect apparently dependent on maintaining high drug levels in the infected reticuloendothelial system.

Vesicular Systems (Niosomes and Liposomes) for Delivery of Sodium Stibogluconate in Experimental Murine Visceral Leishmaniasis

Abstract— Suppression of Leishmania donovani liver amastigotes by sodium stibogluconate has been determined in a murine model of experimental visceral leishmaniasis. Niosomal and liposomal drug formulations were equiactive and both increased drug efficacy by an order of magnitude compared with that of free drug. Niosomes containing 30 mol % cholesterol were prepared from three different non‐ionic surfactants and no significant difference in activity was detected among the different drug‐loaded niosomes. Both negatively charged and neutral vesicles were found to be equally effective. However, vesicle cholesterol content had a slight influence on the antiparasitic activity of the drug‐loaded niosomes. Empty vesicles produced a dose‐dependent parasite suppression for all vesicles studied. Studies of antimony distribution in the mouse using neutron activation analysis showed high liver levels after i.v. administration of the carrier forms of the drug.

The therapeutic effect of sodium stibogluconate in BALB/c mice infected with Leishmania donovani is organ-dependent

Abstract— A study of the antileishmanial efficacy of sodium stibogluconate was carried out in BALB/c mice. The drug was administered to Leishmania donovani‐infected animals on days 7 and 8 post‐infection in one of three forms; free (40–50 mg Sbv Kg−1), liposomal, or niosomal (6.4–8.0 mg Sbv Kg−1) drug. On day 14 post‐infection counts of the number of parasites present in the liver, spleen and bone marrow of treated and control animals showed that although all three drug preparations significantly reduced parasite numbers in the liver (≃99% suppression) they had little effect on those residing in the spleen or bone marrow. The carrier forms of the drug were therefore significantly more effective than free drug in reducing liver parasite burdens. Increasing the concentration and the number of doses of free drug (maximum of 500 mg Sbv Kg−1), and reducing the size of the vesicles used to deliver the drug had a minimal effect on parasite numbers in the spleen and bone marrow. It is proposed that because of the resistance of spleen and bone marrow parasites to drug therapy, the BALB/c mouse infected with L. donovani provides an excellent model system for the study of drug delivery to these deeper tissue sites.

Visceral leishmaniasis: drug carrier system characteristics and the ability to clear parasites from the liver, spleen and bone marrow in Leishmania donovani infected BALB/c mice

Abstract— The efficacy of various sodium stibogluconate formulations against Leishmania donovani has been investigated using a BALB/c mouse model of visceral leishmaniasis. Only one therapy, multiple dosing with drug loaded sonicated vesicles, liposomes or niosomes, was found to be effective against parasites in the liver, spleen and bone marrow. Other treatments significantly reduced parasite liver burdens but either failed to effect spleen and bone marrow parasites, or were effective but toxic. Prophylactic treatment with sodium stibogluconate preparations, six days before infection, reduced parasite multiplication in the liver (free, niosomal and liposomal drug) and the spleen (sonicated, drug loaded niosomes only), but had no suppressive effect on bone marrow parasite burdens compared with controls. These results indicate that in‐vivo sodium stibogluconate persists in some compartments at parasiticidal concentrations and that failure to reach this concentration at some sites of infection such as bone marrow, is the cause of treatment failure and relapse.

Enhanced activity of streptomycin and chloramphenicol against intracellular Escherichia coli in the J774 macrophage cell line mediated by liposome delivery.

Streptomycin and chloramphenicol were entrapped within large neutral or anionic unilamellar vesicles of egg phosphatidylcholine prepared by an ether injection method. Both antibiotics in liposomal form were inactive against Escherichia coli in a simple tube dilution assay. A comparison was made of the activities of the free and liposomal forms of the antibiotics against E. coli located within the macrophages of the J774.2 murine cell line. The apparent intracellular antibacterial activity of both antibiotics was increased more than 10-fold by entrapment in neutral liposomes and in the case of chloramphenicol in anionic liposomes containing phosphatidylserine. Anionic liposomes containing phosphatidic acid were much less effective carriers than neutral liposomes for either antibiotic in this in vitro system. Incubation at 4 degrees C of cells with liposomes containing antibiotic or carboxyfluorescein inhibited intracellular antibacterial activity and cell-associated fluorescence. The high intracellular activity of the liposomal antibiotics is consistent with their phagocytic uptake by the macrophages followed by intracellular liposomal degradation and antibiotic release. Liposomal modification of cellular uptake and intracellular distribution of antibiotics may be used to extend the activity of existing and new agents against intracellular infection of the reticuloendothelial system. Images

Biodegradable microspheres†: polyacryl starch microparticles as a delivery system for the antileishmanial drug, sodium stibogluconate

Liver parasite burdens of Leishmania donovani in the mouse have been determined after treatment with intravenous administration of sodium stibogluconate in the free or carrier form. The carrier form, in which the drug was covalently bound to polyacryl starch microparticles, was up to 100 x more effective than the free form in this murine model of visceral leishmaniasis. Empty microparticles had no effect on liver parasite burdens and the enhanced in‐vivo antileishmanial activity of the carrier form of the drug was apparently due to passive drug delivery to the infected liver.

Thermographic assessment of patch‐test responses

Infra‐red thermography was used to quantify, at patch test sites, the allergic responses to experimental preparations of nickel sulphate and primary irritant responses to sodium lauryl sulphate in small groups of volunteers. The technique was also used to assess the patch‐test responses in a much larger group of patients who had undergone routine patch testing for contact allergy with a wide range of test substances and among which there were large numbers of allergic, irritant and equivocal reactions. Thermographically, when compared to the surrounding normal skin surface, the sites of allergic reactions appeared as hot areas, the temperature and area of which were apparently dependent on the severity of the response. For allergic responses, there was a good correlation between the clinical assessment and either of two thermographic parameters, temperature and area of involvement. Compared with an aqueous solution of nickel sulphate, ‘poor’ formulations of the allergen, such as a suspension in soft paraffin base, elicited smaller and cooler reactions. Irritant reaction sites were not ‘hot’ and the temperature at such sites was no different from that of the surrounding normal skin. Infra‐red thermography is a convenient non‐invasive technique which apparently can be used to discriminate between irritant and allergic responses and to quantify the latter type of response.

Patch testing for nickel allergy The influence of the vehicle on the response rate to topical nickel sulphate

A group of 43 patients with a clinical history of nickel allergy who exhibited an equivocal or no allergic reaction to a patch test al 48 h were further challenged using several different formulations of nickel sulphate. This experimental test battery comprised aqueous, dimethyl sulphoxide (DMSO) and propylene glycol(PG) solutions of nickel sulphate, and nickel sulphate incorporated into cetomacrogol cream and yellow soft paraffin (PMF).

Visceral Leishmaniasis in the BALB/c Mouse: A Comparison of the in Vivo Activity of Five Non-Ionic Surfactant Vesicle Preparations of Sodium Stibogluconate

Five non-ionic surfactants (Surfactants V-IX) were screened for their ability to produce vesicles for the delivery of sodium stibogluconate. Mean vesicle diameter and antimony content were determined prior to in vivo assessment of antiparasitic activity in a mouse model of acute visceral leishmaniasis. V/D suspensions (i.e. stibogluconate loaded vesicles kept in the hydrating drug solution) were more effective against spleen, liver and bone marrow parasites than drug loaded vesicle suspensions that had unentrapped drug removed. A Surfactant IX V/D suspension was the most active antileishmanial preparation causing 74 +/- 10%, 99 +/- 1% and 38 +/- 8% suppression of liver, spleen and bone marrow parasite burdens respectively. Contrary to previous findings, a reduction in splenic and bone marrow parasite burdens was achieved using large vesicles (mean diameter > 800nm). The significance of these results is discussed.

Visceral leishmaniasis in the BALB/c mouse: sodium stibogluconate treatment during acute and chronic stages of infection

The effect of initiating drug treatment (free, liposomal or surfactant vesicle forms of stibogluconate) at different times post-infection in Leishmania donovani infected BALB/c mice was studied. It was found that free stibogluconate therapy was less effective at the later stages of infection, i.e. there was a right shifting of the dose response curve. Treatment with either carrier form of the drug was less sensitive to the length of infection so that the benefit obtained by using this form of the drug dramatically increased over the course of infection. The liposomal and surfactant vesicle forms of the drug were equally effective and they were always more suppressive than the free drug. It is proposed that the successful therapeutic outcome of drug treatment is dependent on the interaction of the innate antileishmanial activity of the drug and a host factor(s), which can either augment or reduce the inherent activity of the drug.