Comparison of the oral bioavailability and tissue disposition of monensin and salinomycin in chickens and turkeys

Population Pharmacokinetics and Absolute Oral Bioavailability of Lasalocid after Single Intravenous and Intracrop Administration in Laying Hens

Lasalocid sodium is a polyether carboxylic ionophore agent authorized by the EU for use as a coccidiostat in broilers, turkeys, and pullets up to 16 weeks of age, except for laying hens. However, laying hens are the most common nontarget species exposed to lasalocid sodium, mainly due to cross-contamination from feed mills. This exposure may result in potential drug residue deposition in eggs, which could potentially expose consumers to the drug. The breeds commonly used for commercial egg production in Poland are Isa Brown and Green-legged Partridge hens, which have been found to significantly differ in egg-laying performance. This variability may also affect the pharmacokinetics of lasalocid. Data on lasalocid plasma pharmacokinetics in laying hens are lacking. In this study, we aimed to determine typical population pharmacokinetic parameters, absolute oral bioavailability, and how breed may influence the pharmacokinetics of lasalocid. Twenty-layer hens of the two breeds were used in this study. Lasalocid was administered orally at a single dose of either 1 mg or 5 mg/kg body weight or intravenously at a dose of 1 mg/kg body weight, in a crossover design with a three-week washout period between study periods. Blood samples were collected for 72 h, and lasalocid concentrations were measured using high-performance liquid chromatography with fluorescence detection. A population pharmacokinetic analysis was conducted using nonlinear mixed effects modeling. Standard numerical and graphical criteria were used to select the best model, and a stepwise covariate modeling approach was used to determine any influencing factors. The best model was a three-compartment mammillary model with first-order absorption, transit compartments, and linear elimination. The estimated absolute oral bioavailability was low (36%). It was found that breed significantly influenced not only absorption but also the elimination of lasalocid. This study revealed that lasalocid absorption and elimination varied between the two breeds. This variability in pharmacokinetics may result in breed-related differences in drug residue accumulation in eggs, and ultimately, the risk associated with consumer exposure to drug residues may also vary.

A generic avian physiologically-based kinetic (PBK) model and its application in three bird species

Physiologically-based kinetic (PBK) models are effective tools for designing toxicological studies and conducting extrapolations to inform hazard characterization in risk assessment by filling data gaps and defining safe levels of chemicals. In the present work, a generic avian PBK model for male and female birds was developed using PK-Sim and MoBi from the Open Systems Pharmacology Suite (OSPS). The PBK model includes an ovulation model (egg development) to predict concentrations of chemicals in eggs from dietary exposure. The model was parametrized for chicken (Gallus gallus), bobwhite quail (Colinus virginianus) and mallard duck (Anas platyrhynchos) and was tested with nine chemicals for which in vivo studies were available. Time-concentration profiles of chemicals reaching tissues and egg compartment were simulated and compared to in vivo data. The overall accuracy of the PBK model predictions across the analyzed chemicals was good. Model simulations were found to be in the range of 22-79% within a 3-fold and 41-89% were within 10- fold deviation of the in vivo observed data. However, for some compounds scarcity of in-vivo data and inconsistencies between published studies allowed only a limited goodness of fit evaluation. The generic avian PBK model was developed following a "best practice" workflow describing how to build a PBK model for novel species. The credibility and reproducibility of the avian PBK models were scored by evaluation according to the available guidance documents from WHO (2010), and OECD (2021), to increase applicability, confidence and acceptance of these in silico models in chemical risk assessment.

Ionophore coccidiostats - disposition kinetics in laying hens and residues transfer to eggs

Poultry production is linked with the use of veterinary medicinal products to manage diseases. Ionophore coccidiostats have been permitted for use as feed additives within the European Union (EU) for the prevention of coccidiosis in various species of poultry with except of laying hens. The presence of chemical residues in eggs is a matter of major concern for consumers' health. Despite such prohibition of use in laying hens, they were identified as the most common non-target poultry species being frequently exposed to these class of coccidiostats. Many factors can influence the presence of residues in eggs. Carryover of these class of coccidiostat feed additives in the feed of laying hens has been identified as the main reason of their occurrence in commercial poultry eggs. The physicochemical properties of individual compounds, the physiology of the laying hen, and the biology of egg formation are believed to govern the residue transfer rate and its distribution between the egg white and yolk compartments. This paper reviews the causes of occurrence of residues of ionophore coccidiostats in eggs within the EU with special emphasis on their disposition kinetics in laying hens, and residue transfer into eggs. Additional effort was made to highlight future modeling perspectives on the potential application of pharmacokinetic modeling in predicting drug residue transfer and its concentration in eggs.

Effects of salinomycin and ethanamizuril on the three microbial communities in vivo and in vitro

The fate of a drug is not only the process of drug metabolism in vivo and in vitro but also the homeostasis of drug-exposed microbial communities may be disturbed. Anticoccidial drugs are widely used to combat the detrimental effects of protozoan parasites in the poultry industry. Salinomycin and ethanamizuril belong to two different classes of anticoccidial drugs. The effect of salinomycin and ethanamizuril on the microbiota of cecal content, manure compost, and soil remains unknown. Our results showed that although both salinomycin and ethanamizuril treatments suppressed some opportunistic pathogens, they failed to repair the great changes in chicken cecal microbial compositions caused by coccidia infection. Subsequently, the metabolite5 profiling of cecal content by LC-MS/MS analyses confirmed the great impact of coccidia infection on chicken cecum and showed that histidine metabolism may be the main action pathway of salinomycin, and aminoacyl tRNA biosynthesis may be the major regulatory mechanism of ethanamizuril. The microbial community of manure compost showed a mild response to ethanamizuril treatment, but ethanamizuril in soil could promote Actinobacteria reproduction, which may inhibit other taxonomic bacteria. When the soil and manure were exposed to salinomycin, the Proteobacteria abundance of microbial communities showed a significant increase, which suggested that salinomycin may improve the ability of the microbiota to utilize carbon sources. This hypothesis was confirmed by a BIOLOG ECO microplate analysis. In the animal model of coccidia infection, the treatment of salinomycin and ethanamizuril may reconstruct a new equilibrium of the intestinal microbiota. In an in vitro environment, the effect of ethanamizuril on composting and soil microbiota seems to be slight. However, salinomycin has a great impact on the microbial communities of manure composting and soil. In particular, the promoting effect of salinomycin on Proteobacteria phylum should be further concerned. In general, salinomycin and ethanamizuril have diverse effects on various microbial communities.

Effects of D-α-tocopherol polyethylene glycol succinate-emulsified poly(lactic-co-glycolic acid) nanoparticles on the absorption, pharmacokinetics, and pharmacodynamics of salinomycin sodium

Although salinomycin sodium (SS) has shown in-vitro potential to inhibit cancer stem cell growth and development, its low water solubility makes it a poor candidate as an oral chemotherapeutic agent. To improve the bioavailability of SS, SS was encapsulated here using D-α-tocopherol polyethylene glycol succinate (TPGS)-emulsified poly(lactic-co-glycolic acid) (PLGA) nanoparticles and compared with its parent SS in terms of absorption, pharmacokinetics, and efficacy in suppressing nasopharyngeal carcinomas stem cells. The pharmacokinetics of SS and salinomycin sodium-loaded D-α-tocopherol polyethylene glycol succinate-emulsified poly(lactic-co-glycolic acid) nanoparticles (SLN) prepared by nanoprecipitation were analyzed in-vivo by timed-interval blood sampling and oral administration of SS and SLN to rats. Sensitive liquid chromatography-mass spectrometry (LC-MS) was developed to quantify plasma drug concentrations. SS and SLN transport in Caco-2 cells was also investigated. The therapeutic efficacy of SS and SLN against cancer stem cells was determined by orally administering the drugs to mice bearing CNE1 and CNE2 nasopharyngeal carcinoma xenografts and then evaluating CD133 cell proportions and tumorsphere formation. The in-vivo trial with rats showed that the Cmax, AUC(0-t), and Tmax for orally administered SLN were all significantly higher than those for SS (P<0.05). These findings were corroborated by a Caco-2 cell Transwell assay showing that relative SLN absorption was greater than that of SS on the basis of their apparent permeability coefficients (Papp). Significantly, therapeutic SLN efficacy against nasopharyngeal carcinoma stem cells was superior to that of SS. TPGS-emulsified PLGA nanoparticles effectively increase SS solubility and bioavailability. SLN is, therefore, promising as an oral chemotherapeutic agent against cancer stem cells.

An open source physiologically based kinetic model for the chicken (Gallus gallus domesticus): Calibration and validation for the prediction residues in tissues and eggs

Xenobiotics from anthropogenic and natural origin enter animal feed and human food as regulated compounds, environmental contaminants or as part of components of the diet. After dietary exposure, a chemical is absorbed and distributed systematically to a range of organs and tissues, metabolised, and excreted. Physiologically based kinetic (PBK) models have been developed to estimate internal concentrations from external doses. In this study, a generic multi-compartment PBK model was developed for chicken. The PBK model was implemented for seven compounds (with log K_ow range -1.37-6.2) to quantitatively link external dose and internal dose for risk assessment of chemicals. Global sensitivity analysis was performed for a hydrophilic and a lipophilic compound to identify the most sensitive parameters in the PBK model. Model predictions were compared to measured data according to dataset-specific exposure scenarios. Globally, 71% of the model predictions were within a 3-fold change of the measured data for chicken and only 7% of the PBK predictions were outside a 10-fold change. While most model input parameters still rely on in vivo experiments, in vitro data were also used as model input to predict internal concentration of the coccidiostat monensin. Future developments of generic PBK models in chicken and other species of relevance to animal health risk assessment are discussed.

Safety and efficacy of Elancoban® G200 (monensin sodium) for chickens for fattening, chickens reared for laying and turkeys

The feed additive Elancoban® G200, containing the active substance monensin sodium, an ionophore anticoccidial, is intended to control coccidiosis in chickens for fattening, chickens reared for laying and turkeys. The FEEDAP Panel cannot conclude on the safety of the additive for the target species, consumer, user and environment with regard to the safety of the production strain. The following conclusions apply to monensin sodium included in the additive. Based on the available data set, the FEEDAP Panel cannot conclude on the safety of Elancoban® G200 for chickens for fattening. Monensin sodium is safe for turkeys for fattening with a margin of safety of 1.5. Monensin sodium is not genotoxic and not carcinogenic. The pharmacological no observed adverse effect level (NOAEL) of 0.345 mg monensin sodium/kg body weight (bw) per day was identified in dog. The acceptable daily intake (ADI) derived from this NOAEL is 0.003 mg monensin sodium/kg bw applying an uncertainty factor of 100. Elancoban® G200 is safe for the consumer. The existing maximum residue limits (MRLs) ensure consumer safety, provided that the withdrawal period of 1 day is respected. Elancoban® G200 is very irritant for the eye, but it is not a skin irritant. Elancoban® G200 should be regarded as a potential skin and respiratory sensitiser. Inhalation exposure is considered a risk to persons handling the additive. Elancoban® G200 does not pose a risk for the terrestrial compartment, the aquatic compartment and the sediment. The bioaccumulation potential of monensin in the environment is low. Monensin sodium from Elancoban® G200 has the potential to effectively control coccidiosis in chickens for fattening and chickens reared for laying. The FEEDAP Panel cannot conclude on the efficacy Elancoban® G200 as a coccidiostat for turkeys for fattening.

Salinomycin decreases feline sarcoma and carcinoma cell viability when combined with doxorubicin

BACKGROUND

Cancer is a significant health threat in cats. Chemoresistance is prevalent in solid tumors. The ionophore salinomycin has anti-cancer properties and may work synergistically with chemotherapeutics. The purpose of our study was to determine if salinomycin could decrease cancer cell viability when combined with doxorubicin in feline sarcoma and carcinoma cells.

RESULTS

We established two new feline injection-site sarcoma cell lines, B4 and C10, and confirmed their tumorigenic potential in athymic nude mice. B4 was more resistant to doxorubicin than C10. Dose-dependent effects were not observed until 92 μM in B4 cells (p = 0.0006) vs. 9.2 μM (p = 0.0004) in C10 cells. Dose-dependent effects of salinomycin were observed at 15 μM in B4 cells (p = 0.025) and at 10 μM in C10 cells (p = 0.020). Doxorubicin plus 5 μM salinomycin decreased viability of B4 cells compared to either agent alone, but only at supra-pharmacological doxorubicin concentrations. However, doxorubicin plus 5 μM salinomycin decreased viability of C10 cells compared to either agent alone at doxorubicin concentrations that can be achieved in vivo (1.84 and 4.6 μM, p < 0.004). In SCCF1 cells, dose-dependent effects of doxorubicin and salinomycin were observed at 9.2 (p = 0.036) and 2.5 (p = 0.0049) μM, respectively. When doxorubicin was combined with either 1, 2.5, or 5 μM of salinomycin in SCCF1 cells, dose-dependent effects of doxorubicin were observed at 9.2 (p = 0.0021), 4.6 (p = 0.0042), and 1.84 (p = 0.0021) μM, respectively. Combination index calculations for doxorubicin plus 2.5 and 5 μM salinomycin in SCCF1 cells were 0.4 and 0.6, respectively.

CONCLUSIONS

We have developed two new feline sarcoma cell lines that can be used to study chemoresistance. We observed that salinomycin may potentiate (C10 cells) or work synergistically (SCCF1 cells) with doxorubicin in certain feline cancer cells. Further research is indicated to understand the mechanism of action of salinomycin in feline cancer cells as well as potential tolerability and toxicity in normal feline tissues.

Influence of mycotoxin binders on the oral bioavailability of tylosin, doxycycline, diclazuril, and salinomycin in fed broiler chickens

The presence of mycotoxins in broiler feed can have deleterious effects on the wellbeing of the animals and their performance. Mycotoxin binders are feed additives that aim to adsorb mycotoxins in the intestinal tract and thereby prevent the oral absorption of the mycotoxin. The simultaneous administration of coccidiostats and/or antimicrobials with mycotoxin binders might lead to a reduced oral bioavailability of these veterinary medicinal products. This paper describes the influence of 3 mycotoxin binders (i.e., clay 1 containing montmorillonite, mica, and feldspars; clay 2 containing montmorillonite and quartz; and yeast 1 being a modified glucomannan fraction of inactivated yeast cells) and activated carbon on the oral bioavailability and pharmacokinetic parameters of the antimicrobials doxycycline and tylosin, and the coccidiostats diclazuril and salinomycin. A feeding study with 40 15 day-old broilers was performed evaluating the effects of long-term feeding 2 g mycotoxin binder/kg of feed. The birds were randomly divided into 5 groups of 8 birds each, i.e., a control group receiving no binder and 4 test groups receiving either clay 1, clay 2, yeast 1, or activated carbon mixed in the feed. After 15 d of feeding, both the control and each test group were administered doxycycline, tylosin, diclazuril, and salinomycin, consecutively, respecting a wash-out period of 2 to 3 d between each administration. The 4 medicinal products were dosed using a single bolus administration directly in the crop. After each bolus administration, blood was collected for plasma analysis and calculation of the main pharmacokinetic parameters and relative oral bioavailability (F = area under the plasma concentration-time curve (AUC0-8 h) in the test groups/AUC0-8 h in the control group)*100). No effects were observed of any of the mycotoxin binders on the relative oral bioavailability of the coccidiostats (i.e., F between 82 and 101% and 79 and 93% for diclazuril and salinomycin, respectively). Also, no significant effects could be noticed of any of the mycotoxin binders on the relative oral bioavailability of the antimicrobials doxycycline and tylosin (i.e., F between 67 and 83% and between 43 and 104%, respectively).

Survival After Severe Rhabdomyolysis Following Monensin Ingestion

INTRODUCTION

Monensin is a veterinary antibiotic with a narrow therapeutic window that has led to lethal intoxication in many animal species. Only two prior cases of human toxicity have been reported, both fatal. We present the first case of survival from severe toxicity following monensin ingestion.

CASE

A 58-year-old man presented with 8 days of vomiting and abdominal pain. Due to delusions of central nervous system toxoplasmosis, he ingested 300 mg of monensin. His laboratory studies revealed severe rhabdomyolysis without renal dysfunction. Total creatine kinase (CK) peaked above 100,000 U/L. His CK decreased to 5192 U/L after 15 days of aggressive hydration and sodium bicarbonate therapy. His ejection fraction on echocardiogram decreased from 69 to 56%.

DISCUSSION

Reports on acute clinical effects after human exposure to monensin are limited. Ingestion is known to cause skeletal and cardiac muscle rhabdomyolysis and necrosis. Animal studies demonstrate that monensin's toxicity is due to increases in intracellular sodium concentrations and Ca²⁺ release. To date, no effective antidotal treatment has been described.

CONCLUSIONS

Monensin is a veterinary medication not approved for human use by the US Food and Drug Administration. Though poorly studied in humans, this case demonstrates the severe harm that may occur following ingestion.

Specific targeting of neurotoxic side effects and pharmacological profile of the novel cancer stem cell drug salinomycin in mice

Salinomycin is a polyether antibiotic which effectively eliminates a variety of cancer stem cells and chemotherapy-resistant tumor cells in vitro and in vivo. One important caveat for its clinical application is the paucity of preclinical pharmacological and safety data. In the present study, we thus aimed to elucidate pharmacokinetic properties of salinomycin and to assess the side effect profile of chronic treatment with this compound in C57Bl/6 mice. In addition, we tested whether neurotoxic side effects can be prevented by interference with the intracellular calcium homeostasis. We observed that salinomycin has a narrow therapeutic index; however, a dose of 5 mg/kg body weight was well tolerated, and analysis of blood parameters as well as organ histology of liver, kidney, skeletal muscle, and heart showed no abnormalities after daily salinomycin injection for 4 weeks. Pharmacokinetic evaluation revealed low micromolar peak concentrations and an almost complete systemic elimination within 5 h after injection. In contrast to low systemic toxicity, typical signs of a sensory polyneuropathy with mechanical and cold allodynia, distinct gait alterations, decreased sensory nerve action potential amplitudes, and loss of myelinated fibers in the sciatic nerve were observed in salinomycin-treated animals. Inhibition of the mitochondrial Na(+)/Ca(2+) exchanger partially prevented the development of salinomycin-induced neuropathy in vivo, an approach which did not reduce salinomycin's antineoplastic efficacy in vitro. Taken together, this study establishes a framework of pharmacokinetic data for future preclinical trials and safety data for translational trials. Furthermore, we established a strategy to reduce salinomycin's off-target neurotoxic effects.

KEY MESSAGE

Salinomycin has a narrow therapeutic index; a dose of 5 mg/kg is tolerated in mice. Mice treated with salinomycin develop a painful sensory polyneuropathy. An optimized protocol was established to measure salinomycin in serum samples. Inhibition of Na(+)/Ca(2+) exchangers prevents salinomycin-induced neuropathy. Blocking mitochondrial Na(+)/Ca(2+) exchangers does not impair antineoplastic efficacy.

Salinomycin: a novel anti-cancer agent with known anti-coccidial activities

Salinomycin, traditionally used as an anti-coccidial drug, has recently been shown to possess anti-cancer and anti-cancer stem cell (CSC) effects, as well as activities to overcome multi-drug resistance based on studies using human cancer cell lines, xenograft mice, and in case reports involving cancer patients in pilot clinical trials. Therefore, salinomycin may be considered as a promising novel anti-cancer agent despite its largely unknown mechanism of action. This review summarizes the pharmacologic effects of salinomycin and presents possible mechanisms by which salinomycin exerts its anti-tumorigenic activities. Recent advances and potential complications that might limit the utilization of salinomycin as an anti-cancer and anti-CSC agent are also presented and discussed.

Salinomycin, a polyether ionophoric antibiotic, inhibits adipogenesis

The polyether ionophoric antibiotics including monensin, salinomycin, and narasin, are widely used in veterinary medicine and as food additives and growth promoters in animal husbandry including poultry farming. Their effects on human health, however, are not fully understood. Recent studies showed that salinomycin is a cancer stem cell inhibitor. Since poultry consumption has risen sharply in the last three decades, we asked whether the consumption of meat tainted with growth promoting antibiotics might have effects on adipose cells. We showed in this report that the ionophoric antibiotics inhibit the differentiation of preadipocytes into adipocytes. The block of differentiation is not due to the induction of apoptosis nor the inhibition of cell proliferation. In addition, salinomycin also suppresses the transcriptional activity of the CCAAT/enhancer binding proteins and the peroxisome proliferator-activated receptor γ. These results suggest that the ionophoric antibiotics can be exploited as novel anti-obesity therapeutics and as pharmacological probes for the study of adipose biology. Further, the pharmacological effects of salinomycin could be a harbinger of its toxicity on the adipose tissue and other susceptible target cells in cancer therapy.