Vitamins E and A increase the passing of the P-gp substrate ivermectin into the brain in mice.

This study aimed to determine the effect of administration of oral vitamins A and E at different doses on plasma and brain concentrations of ivermectin in mice. The study was carried out on 174 Swiss Albino male mice aged 8-10 weeks. After leaving six mice for method validation, the remaining mice were randomly divided into seven groups with equal numbers of animals. Mice received ivermectin (0.2 mg/kg, subcutaneous) alone and in combination with low (vitamin A: 4000 IU/kg; vitamin E: 35 mg/kg) and high (vitamin A: 30 000 IU/kg; vitamin E: 500 mg/kg) oral doses of vitamins A and E. The plasma and brain concentrations of ivermectin were measured using high-performance liquid chromatography-fluorescence detector. We determined that high doses of vitamins A and E and their combinations increased the passing ratio of ivermectin into the brain significantly. The high-dose vitamin E and the combination of high-concentration vitamins E and A significantly increased the plasma concentration of ivermectin (P < 0.05). The high-dose vitamins E and A and their high-dose combination increased the brain concentration of ivermectin by 3, 2, and 2.7 times, respectively. This research is the first in vivo study to determine the interaction between P-gp substrates and vitamins E and A.

Development of (6 R)-2-Nitro-6-[4-(trifluoromethoxy)phenoxy]-6,7-dihydro-5 H-imidazo[2,1- b][1,3]oxazine (DNDI-8219): A New Lead for Visceral Leishmaniasis.

Discovery of the potent antileishmanial effects of antitubercular 6-nitro-2,3-dihydroimidazo[2,1- b][1,3]oxazoles and 7-substituted 2-nitro-5,6-dihydroimidazo[2,1- b][1,3]oxazines stimulated the examination of further scaffolds (e.g., 2-nitro-5,6,7,8-tetrahydroimidazo[2,1- b][1,3]oxazepines), but the results for these seemed less attractive. Following the screening of a 900-compound pretomanid analogue library, several hits with more suitable potency, solubility, and microsomal stability were identified, and the superior efficacy of newly synthesized 6 R enantiomers with phenylpyridine-based side chains was established through head-to-head assessments in a Leishmania donovani mouse model. Two such leads ( R-84 and R-89) displayed promising activity in the more stringent Leishmania infantum hamster model but were unexpectedly found to be potent inhibitors of hERG. An extensive structure-activity relationship investigation pinpointed two compounds ( R-6 and pyridine R-136) with better solubility and pharmacokinetic properties that also provided excellent oral efficacy in the same hamster model (>97% parasite clearance at 25 mg/kg, twice daily) and exhibited minimal hERG inhibition. Additional profiling earmarked R-6 as the favored backup development candidate.

Formulation Studies of Solid Self-Emulsifying Drug Delivery System of Ivermectin.

BACKGROUND: The suggested dose of ivermectin is 300 µG/kg/day for onchocerciasis but it has low water solubility and poor oral bioavailability. AIM: To prepare and evaluate a solid lipid-based self-emulsifying drug delivery system of ivermectin. MATERIALS AND METHODS: Based on supersaturated solubility study, oil, surfactant, and co-surfactant were selected. On the basis of ternary phase diagrams and simplex-lattice design, self-emulsifying, drug delivery formulations had been developed and optimized. Ivermectin-excipients compatibility studies were performed using differential scanning calorimetry and Fourier transform infrared spectroscopy. Solid self-emulsifying drug delivery formulation was formulated from the optimized batch by surface assimilation method and filled into hard gelatin capsules. In vitro release rate and in vivo pharmacokinetic parameters of ivermectin from the capsules were determined. Two-tailed paired t-test/Dunnett multiple comparison tests were performed for in vivo pharmacokinetic parameter at 95 % of confidence level. RESULTS: Soybeans oil, tween 80, and span 80 were selected as oil, surfactant, and co-surfactant respectively. The ternary diagrams were shown the maximum area for emulsion in 1:2 surfactant/co-surfactant ratio. The optimized batch had found with 30 mg ivermectin, 6.17 g soybeans oil, 0.30 g tween 80, and 3.50 g span 80. All differential scanning calorimetry and Fourier transform infrared characteristic peaks of the optimized formulation were identical with that of pure ivermectin. The area under the curve of ivermectin from the capsule was about two-fold higher than that of ivermectin suspension. CONCLUSIONS: Solid self-emulsifying drug delivery system was an effective oral solid dosage form to improve the oral bioavailability of ivermectin.

Sustained release ivermectin-loaded solid lipid dispersion for subcutaneous delivery: in vitro and in vivo evaluation.

This work aimed to develop a sustained release solid dispersion of ivermectin (IVM-SD) in a lipid matrix (hydrogenated castor oil, HCO) for subcutaneous delivery. Solvent-melting technology was employed to prepare IVM-SDs using HCO. The physicochemical properties of the IVM-SDs were evaluated by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), and Fourier transform infrared spectroscopy (FTIR). The release of IVM from IVM-SDs was evaluated with HPLC in vitro. Pharmacokinetics of IVM was studied in rabbits following a single subcutaneous administration of IVM-SD formulations. The efficacy of IVM-SD against the ear mange mite was evaluated in rabbits. IVM was completely dispersed in HCO in an amorphous state at a drug:carrier ratio lower than 1:3. No chemical interactions between drug and carrier were found besides hydrogen bonding for the amorphous IVM-SDs. The amorphous IVM-SDs formulations exhibited a sustained release of IVM versus physical mixtures (PMs) of IVM and HCO. The drug release decreased as the drug:carrier ratios decreased, and the release kinetics of IVM were controlled via diffusion. Cytotoxicity of IVM-SD to MDCK cells was lower than native IVM. The IVM plasma concentration of SD1:3 remained above 1 ng/mL for 49 d. Higher AUC, MRT, and Tmax values were obtained at a SD1:3 relative to the IVM group. The IVM-SD improved almost 1.1-fold bioavailability of drug compared with IVM in rabbits. IVM-SD could provide longer persistence against rabbit's ear mites than a commercial IVM injection. This study shows that these solid lipid dispersions are a promising approach for the development of subcutaneous IVM formulations.

In vitro metabolism, disposition, preclinical pharmacokinetics and prediction of human pharmacokinetics of DNDI-VL-2098, a potential oral treatment for Visceral Leishmaniasis.

The in vitro metabolism and in vivo pharmacokinetic (PK) properties of DNDI-VL-2098, a potential oral agent for Visceral Leishmaniasis (VL) were studied and used to predict its human pharmacokinetics. DNDI-VL-2098 showed a low solubility (10µM) and was highly permeable (>200nm/s) in the Caco-2 model. It was stable in vitro in liver microsomes and hepatocytes and no metabolite was detectable in circulating plasma from dosed animals suggesting very slow, if any, metabolism of the compound. DNDI-VL-2098 was moderate to highly bound to plasma proteins across the species tested (94-98%). DNDI-VL-2098 showed satisfactory PK properties in mouse, hamster, rat and dog with a low blood clearance (<15% of hepatic blood flow except hamster), a volume of distribution of about 3 times total body water, acceptable half-life (1-6h across the species) and good oral bioavailability (37-100%). Allometric scaling of the preclinical PK data to human gave a blood half-life of approximately 20h suggesting that the compound could be a once-a-day drug. Based on the above assumptions, the minimum efficacious dose predicted for a 50kg human was 150mg and 300mg, using efficacy results in the mouse and hamster, respectively.

Los aceites esenciales como agentes antiparasitarios / Essential oils as anti-parasitic agents

La aparición de parásitos resistentes a la terapia, incluyendo protozoos de géneros como Leishmania, Trypanossoma, Giardia y Plasmodium, y/o la falta de eficacia, los efectos secundarios graves y el alto costo de la terapia, hace urgente desarrollar nuevos agentes antiparasitarios. En los últimos años se ha potenciado la búsqueda de nuevos medicamentos alternativos para el tratamiento de las infecciones por parásitos, habiendo aumentado el descubrimiento de potenciales agentes terapéuticos a partir de fuentes naturales como las plantas medicinales y sus extractos, incluyendo los aceites esenciales. Aceites esenciales, tales como los de Cymbopogon citratus, Croton cajucara, Ocimum gratissimum o Thymus vulgaris, han demostrado su actividad antiparasitaria, con un amplio espectro de actividad, a menudo demostrando eficacia equivalente a la quimioterapia establecida (AU)

The emergence of parasites resistant to therapy, namely protozoa of genera Leishmania, Trypanossoma, Giardia, Plasmodium, and/or the lack of efficacy, the occurrence of serious side effects and the high cost of therapy, makes urgent the development of new anti-parasitic agents. In the last years, the search for new alternative drugs for the treatment of parasitic infections have been developed. The discovery of potential therapeutic agents from natural sources such as medicinal plants and their extracts, including essential oils, has increased. Essential oils from Cymbopogon citratus, Croton cajucara, Ocimum gratissimum and Thymus vulgaris, showed anti-parasitic activity with a broad spectrum of activities and often demonstrating equivalent effectiveness to established chemotherapy (AU)

A emergência de parasitas resistentes à terapêutica instituída, designadamente protozoários de géneros como a Leishmania, Trypanossoma, Giardia, Plasmodium, e/ou a falta de eficácia, os efeitos secundários graves e o custo elevado, torna urgente o desenvolvimento de novos agentes anti-parasitários. Nos últimos anos, a pesquisa por fármacos novos e alternativos no tratamento de infecções por parasitas, tem vindo a desenvolver-se. A descoberta de potenciais agentes terapêuticos a partir de fontes naturais como as plantas medicinais e dos seus extractos, nomeadamente os óleos essenciais, tem vindo a aumentar. Os óleos essenciais como o Cymbopogon citratus, o Croton cajucara, o Ocimum gratissimum, ou o Thymus vulgaris, têm demonstrado actividade anti-parasitária com um amplo espectro de actividades evidenciando, muitas vezes, eficácia equivalente à quimioterapia padrão (AU)

Early toxicity screening and selection of lead compounds for parasitic diseases.

Despite many advances made in disease mechanisms knowledge and drug discovery and development processes, the election of promising lead compounds continues to be a challenge. Efficient techniques are required for lead selection of hit compounds selected through in vitro pharmacological studies, in order to generate precise low cost throughput data with minimal amount of compound to support the right decision making. In this context, the selection of lead compounds with physicochemical parameters that will benefit orally bioavailable drugs are crucial for patients compliance and cost effectiveness, as well as for successful pharmacology. A concept based in Lipinski's rules point out the importance of analyzing these informations in early stages. A hepatocyte screening system may provide data on many processes such as drug-drug interaction, metabolite formation, drug toxicity and ADME profile of a hit. Drug-induced liver injury is the most frequent reason for the withdrawal of an approved drug from the market and hepatocytes have a central role in the metabolism of xenobiotics. Cytotoxicity screening assays can also give some information about toxicity early drug discovery process. A set of goals in lead compound selection must be shared between all areas involved so the chances of success can be improved in translational research.

The effect of sesame and sunflower oils on the plasma disposition of ivermectin in goats.

The effect of sesame oil (SSO) and sunflower oil (SFO) (the excipients) on the plasma disposition of ivermectin (IVM) following intravenous (i.v.) and subcutaneous (s.c.) administration at a dosage of 200 microg/kg was investigated in goats. Ten clinically healthy crossbred goats were used in the study. The animals were allocated by weight and sex into two groups of five animals each. Group 1 (n = 5) received the drug and excipient by the i.v. route only and group 2 received drug and excipient by the s.c. route only. The study was designed according to a two-phase crossover design protocol. In the first phase three animals in group 1 were i.v. administered IVM (0.2 mg/kg) + SSO (1 mL) and the other two animals received IVM (0.2 mg/kg) + SFO (1 mL). In the second phase animals were crossed over and received the alternate excipient with IVM at the same dosages. In group 2 during the first phase, three animals were s.c. administered IVM (0.2 mg/kg) + SSO (1 mL) and the other two animals were received IVM (0.2 mg/kg) + SFO (1 mL). In the second phase animals were crossed over and received the alternate excipient with IVM at the same dosages. A 4-week washout period was allowed between the two phases. In group 2 significantly increased dermal thickness was observed at the s.c. injection site of the all animals which received IVM during phase I regardless of the excipient. There was almost no change observed at the injection site of any animal during the second phase of the study following s.c. administration. In group 2 the plasma concentrations of IVM in the second phase for both excipient combinations were much higher than the plasma concentrations following first administration and appeared to be related with the dermal changes. The mean plasma disposition of IVM in combination with SSO or SFO was similar following i.v. administration. Longer terminal elimination half-lives and resultant longer mean resident time were observed after s.c. administration of the both combinations compared with i.v. administration.

Target validation for drug discovery in parasitic organisms.

Parasite infections affect billions of humans world-wide, yet the current drugs available for the treatment of many parasitic diseases are either inadequate, or compromised by the development of resistance. Validation of a drug target is an important step in the development of new drugs. Target validation encompasses verifying that a target is primarily responsible for the therapeutic activity of a proven drug, or demonstrating the essential nature of a putative drug target in a parasite, and the capacity for selective inhibition of that target in vivo. Selective toxicity may be achieved by taking advantage of unique parasite biology or biochemistry, or by utilizing differences in metabolism or import. The essential nature of a target may be demonstrated by the correlation of the chemical or genetic reduction of target activity with the loss of parasite growth or virulence. Rescue experiments may demonstrate the single nature of a target. Ultimately, a target must be validated in vivo.