Mechanism for transport of ivermectin to the stratum corneum in rats

Regression of bovine cutaneous papillomas via ivermectin-induced immunostimulant and oxidative stress

OBJECTIVE

Ivermectin (IVM) could be used effectively to treat bovine cutaneous papillomatosis, a widespread viral skin disease that causes major economic losses in cattle. This study aimed to evaluate the regression of bovine cutaneous papillomas induced by IVM by estimating oxidative stress markers, besides clinicopathological and hematological findings.

MATERIALS AND METHODS

Twenty naturally infected animals with cutaneous papillomatosis were chosen randomly and diagnosed clinically and histopathologically. All the infected animals were divided into groups: Group I (n = 10), which received no treatment and was considered the control group. In Group II (n = 10), the animals were subcutaneously injected at 0.2 mg/kg of IVM 2 weeks apart during the 90-day experimental period. Papilloma regression was tracked clinically, papilloma biopsies were taken for histopathological analysis, and blood samples were taken for hematological and oxidative parameter testing.

RESULTS

From the 15th to 45th day after receiving IVM, papillomas began to fade. Necrotic areas, ulcerations, and lymphocytic infiltration were found in the histopathological studies, besides a decrease in papilloma epidermal proliferation. total erythrocytes count, packed cell volume, total leucocytes count, and lymphocytes values were increased significantly, and a large decrease in glutathione peroxidase and glutathione reduced was identified as signs of IVM-induced oxidative stress.

CONCLUSION

IVM has oxidative and immunostimulatory properties, and it can be used against cutaneous papillomatosis.

Safety, Pharmacokinetics, and Mosquito-Lethal Effects of Ivermectin in Combination With Dihydroartemisinin-Piperaquine and Primaquine in Healthy Adult Thai Subjects

Mass administration of antimalarial drugs and ivermectin are being considered as potential accelerators of malaria elimination. The safety, tolerability, pharmacokinetics, and mosquito‐lethal effects of combinations of ivermectin, dihydroartemisinin‐piperaquine, and primaquine were evaluated. Coadministration of ivermectin and dihydroartemisinin‐piperaquine resulted in increased ivermectin concentrations with corresponding increases in mosquito‐lethal effect across all subjects. Exposure to piperaquine was also increased when coadministered with ivermectin, but electrocardiograph QT‐interval prolongation was not increased. One subject had transiently impaired liver function. Ivermectin mosquito‐lethal effect was greater than predicted previously against the major Southeast Asian malaria vectors. Both Anopheles dirus and Anopheles minimus mosquito mortality was increased substantially (20‐fold and 35‐fold increase, respectively) when feeding on volunteer blood after ivermectin administration compared with in vitro ivermectin‐spiked blood. This suggests the presence of ivermectin metabolites that impart mosquito‐lethal effects. Further studies of this combined approach to accelerate malaria elimination are warranted.

Utility of hairless rats as a model for predicting transdermal pharmacokinetics in humans

This study investigated the use of HWY hairless rats to predict human plasma concentrations of drugs following dermal application.Utilizing a deconvolution method, pharmacokinetic parameters (e.g. in vivo absorption rates) were determined for six transdermal drugs in hairless rats. Obtained data were used to simulate the human plasma concentration-time profiles of transdermal drugs, which were then compared with clinical data in humans. Because hairless rats have lower hair follicle density than do humans, the impact of hair follicle density on skin permeability to hydrophilic compounds was also evaluated.Pharmacokinetic parameters showed low intra-individual variability in hairless rats. Simulated concentration profiles for compounds with logarithm of the octanol-water partition coefficient exceeding two were comparable to clinical data, but simulated concentration profiles for hydrophilic compounds (i.e. bisoprolol and nicotine) at maximum concentration differed from clinical data by more than two-fold. Finally, in vitro permeability to bisoprolol and nicotine was higher in human skin than in hairless rat skin, but hair follicle plugging reduced human skin permeability.In vivo skin absorption data from HWY hairless rats help to predict human concentration profiles for lipophilic compounds. However, the data underestimate human absorption of hydrophilic compounds.

Pharmacokinetics of ivermectin applied topically by whole-body bathing method in healthy volunteers

As a novel administration method of ivermectin (IVM) for scabies treatment, we proposed a "whole-body bathing method (WBBM)". In this method, the patients would bathe themselves in a bathing fluid containing IVM at an effective concentration. Previously, we demonstrated that WBBM could deliver IVM to the skin but not to the plasma in rats. In the present study, to assess the clinical validity of the method an arm bathing examination (first trial) and a whole-body bathing examination (second trial) were conducted in healthy volunteers. In both the first and second trials, after bathing in fluid containing IVM, the exposure in the stratum corneum was higher compared with that after taking IVM p.o. as reported previously. IVM was not detected in plasma at any sampling point after the whole-body bathing in the second trial. Furthermore no serious adverse events were found. These results in both trials suggest that WBBM can deliver IVM to the human stratum corneum without systemic exposure or serious adverse effects in healthy volunteers, and at concentrations that would be adequate for scabies treatment.

Preclinical Study of Single-Dose Moxidectin, a New Oral Treatment for Scabies: Efficacy, Safety, and Pharmacokinetics Compared to Two-Dose Ivermectin in a Porcine Model

Background

Scabies is one of the commonest dermatological conditions globally; however it is a largely underexplored and truly neglected infectious disease. Foremost, improvement in the management of this public health burden is imperative. Current treatments with topical agents and/or oral ivermectin (IVM) are insufficient and drug resistance is emerging. Moxidectin (MOX), with more advantageous pharmacological profiles may be a promising alternative.

Methodology/Principal Findings

Using a porcine scabies model, 12 pigs were randomly assigned to receive orally either MOX (0.3 mg/kg once), IVM (0.2 mg/kg twice) or no treatment. We evaluated treatment efficacies by assessing mite count, clinical lesions, pruritus and ELISA-determined anti-S. scabiei IgG antibodies reductions. Plasma and skin pharmacokinetic profiles were determined. At day 14 post-treatment, all four MOX-treated but only two IVM-treated pigs were mite-free. MOX efficacy was 100% and remained unchanged until study-end (D47), compared to 62% (range 26–100%) for IVM, with one IVM-treated pig remaining infected until D47. Clinical scabies lesions, pruritus and anti-S. scabiei IgG antibodies had completely disappeared in all MOX-treated but only 75% of IVM-treated pigs. MOX persisted ~9 times longer than IVM in plasma and skin, thereby covering the mite’s entire life cycle and enabling long-lasting efficacy.

Conclusions/Significance

Our data demonstrate that oral single-dose MOX was more effective than two consecutive IVM-doses, supporting MOX as potential therapeutic approach for scabies.

Scabies caused by the Sarcoptes scabiei mite affects many people worldwide and has been recently recognized by the WHO as a truly neglected tropical disease. Currently available treatments are insufficient to overcome this insidious disease and its co-morbidities for example impetigo, rheumatic heart disease and post-streptococcal glomerulonephritis. Treatment management is a major issue, as problems with compliance as well as mite resistance to current drugs are reported. Data have accumulated indicating that moxidectin could be a genuine new candidate drug for sustainable scabies control. To provide proof of concept, we utilized an experimental scabies pig model that closely resembles the human route of scabies infection. We demonstrated that a single moxidectin dose, when compared with the currently recommended two-doses ivermectin treatment routine, achieved a better and faster acaricidal efficacy. Importantly, the skin half-life of moxidectin is longer, potentially covering the entire mite life cycle. Our baseline data demonstrate in principle the potential and feasibility of moxidectin treatment for scabies, thereby enabling the move into larger high-powered efficacy and dose ranging studies in human populations. Moxidectin could indeed play a game-changing role in scabies control and has the potential to accelerate the steps towards elimination of this insidious disease.

Effect of high-fat meal intake on the pharmacokinetic profile of ivermectin in Japanese patients with scabies

Ivermectin (IVM) is used as an anthelmintic agent in many countries. To evaluate the effect of high-fat (HF) meal intake on the pharmacokinetics of IVM, a clinical trial was conducted in Japanese patients with scabies. The patients were administrated Stromectol(®) tablets in the fasted state, and after 1 week they were also administrated it after a HF meal (fed state). After the administration, IVM concentrations in plasma and the stratum corneum were determined. The geometric mean of fed/fasted ratio of area under IVM concentration-time curve (AUC) in plasma was 1.25 (90% confidence interval, 1.09-1.43), suggesting the tendency to increased absorption after a HF meal. The fed/fasted ratio of the maximum IVM concentration in the stratum corneum was well correlated with that in plasma. In addition, no serious adverse events were observed during the trial, while a mild increase of aspartate aminotransferase and alanine aminotransferase activity in plasma was observed under the fed state in two patients. The mean AUC of IVM in plasma of those two patients were approximately threefold higher than that of the other patients at that time. On the other hand, the treatment success rate was 76.9% at 7 days after the second administration, which was comparable with the expected level. The present study not only demonstrates that HF meal intake increases the IVM concentration in plasma and the stratum corneum in Japanese patients with scabies, but also suggests the possibility that HF meals increase the risk of hepatic dysfunction by the increased exposure of IVM.