Pharmacokinetics of Metformin in Combination With Sitagliptin in Adult Horses After Enteral Administration

An in vivo pharmacokinetic study of metformin microparticles as an oral sustained release formulation in rabbits

BACKGROUND

Metformin hydrochloride is a biguanide derivative that has been widely used to treat type 2 diabetes in humans. In veterinary medicine, metformin has shown increasing potential for diabetes treatment in different species, such as equids, dogs, cats and rabbits. It is highly hydrophilic, with incomplete gastrointestinal absorption and very large variability in absolute bioavailability between species, ranging from 4% in equids to 60% in humans. Metformin also shows a short half-life of approximately 2 h in dogs, cats, horses and humans. The objectives of this study were to evaluate a poly (lactic acid) (PLA) metformin microparticle formulation to test in rabbits and conduct a pharmacokinetics study of intravenous (S_IV) and oral solution (S_PO) metformin administration and oral PLA microparticle (S_PLA) administration to rabbits to evaluate the improvement in the metformin pharmacokinetics profile.

RESULTS

Metformin-loaded PLA microparticles were characterized by a spherical shape and high encapsulation efficiency. The results from Fourier transform infrared (FTIR) spectroscopy suggested the presence of interactions between metformin and PLA. X-Ray diffraction (XRD) analysis corroborated the results from the differential scanning calorimetry (DSC) studies, showing that metformin is present in an amorphous state within the microparticles. Physicochemical characterization suggested that PLA and metformin hydrochloride interacted within the microparticles via hydrogen bonding interactions. The pharmacokinetic study in rabbits showed sustained-release characteristics from the prepared microparticles with a delay in the time needed to reach the maximum concentration (T_max), decreased C_max and bioavailability, and increased mean residence time (MRT) and half-life compared to the pure drug solution.

CONCLUSIONS

Metformin-loaded PLA microparticles showed optimal and beneficial properties in terms of their physicochemical characteristics, making them suitable for use in an in vivo pharmacokinetic study. The pharmacokinetic parameters of the metformin microparticles from the in vivo study showed a shorter T_max, longer MRT and half-life, decreased C_max and the prolonged/sustained release expected for metformin. However, the unexpected decrease in bioavailability of metformin from the microparticles with respect to the oral solution should be evaluated for microparticle and dose design in future works, especially before being tested in other animal species in veterinary medicine.

A review of recent developments in the pharmacological prevention and treatment of endocrinopathic laminitis

Despite the prevalence of endocrinopathic laminitis, the pharmacologic options for preventing and treating the disease are severely limited. The present review aims to discuss the spectrum of potential therapeutic agents for the condition, ranging from early experimental compounds to agents nearing registration. There are different pharmacologic targets for, and approaches to, managing laminitis. Reducing hyperinsulinaemia is central to diminishing endocrinopathic laminitis risk, and a detailed understanding of the pathophysiology of insulin dysregulation is necessary to identify pathways that can be targeted to minimise post-prandial insulin secretion and action. This area of research is advancing rapidly, with several exciting prospects, such as sodium-dependent glucose co-transporter-2 inhibitors, on the horizon for the treatment of equine metabolic dysfunction. Drugs that directly target the lamellae and aim to reduce the damage inflicted on the lamellae as part of this condition, are not yet available. Although progress in this area of laminitis therapy is slower, improved understanding of the events that lead to lamellar failure has enabled the investigation of novel drugs that aim to prevent laminitis at the site of the lesion. Finally, a brief review is included of the directions being taken in the management of the chronic and acute pain that accompanies laminitis. Medications for relieving the pain associated with laminitis are currently the most-prescribed drugs for the disease, and range from simple, affordable and thoroughly tested options, such as phenylbutazone, to newer, less-understood applications such as paracetamol and gabapentin. In the future, endocrinopathic laminitis management plans will likely take a multi-faceted approach that still hinge on effective dietary management and exercise, but also include drugs that address foot pathology, pain and underlying endocrine disturbances.

Sitagliptin protects liver against aflatoxin B1-induced hepatotoxicity through upregulating Nrf2/ARE/HO-1 pathway

Dipeptidyl peptidase-4 inhibitor (DPP-4 inhibitor) such as sitagliptin has been presented as antidiabetic drugs and has numerous restorative advantages over different diseases; however, its defensive role against aflatoxin b1 (AFB1) liver toxicity has not been previously examined. Wistar rats (65 weeks, male) were utilized in the investigation. Animals were divided into five different groups (n = 10): control; AFB1; AFB1 + Sita (50); AFB1 + Sita (100); and Sita (100). Sitagliptin significantly (*p ≤ .05, **p ≤ .01, and ***p ≤ .001) altered the levels of various serum liver enzymes (lactate dehydrogenase, alkaline phosphate, aspartate aminotransferase, and alanine aminotransferase). It decreased the concentration of an oxidative stress marker, that is, malondialdehyde and increased the level of antioxidant enzymes such as reduced glutathione, catalase, superoxide dismutase, and glutathione peroxidase in AFB1-administered rats. It also improved the Nrf2 expression and HO-1 level in AFB1-intoxicated rats. This investigation discusses innovative evidence on the protective role of sitagliptin against AFB1-induced hepatotoxicity in rats.