Aportaciones al tratamiento de diarreas crónicas inespecíficas en el perroestudio del perfil farmacocinético de infliximab, tilosina y transferencia de microbiota fecal

Abstract

For FMT study, two groups were used following the same protocol. One group consisted of patients from the Veterinary Hospital of the University of Murcia: dogs with chronic enteropathies (more than 3 weeks of duration), diagnosed with IBD at different levels (stomach, duodenum or colon mainly) by endoscopic biopsy. A second group consisted of patients from the veterinary clinic for small species Hinckley Vets4pets (England): dogs with chronic diarrhea with partial response to antibiotic treatment initially treated with metronidazole and that relapsed. In all cases, the owners authorized the performance of one or two TMF and provided information on the clinical evolution of the animal. A point-based classification of inflammatory bowel disease was performed, following the "Canine Inflammatory Diease Activity Index" (CIBDAI index described by Jergens et al. (2003)). For stool grading, the "Waltham faeces scoring system" was used. Transplants were performed, 48h after tylosin administration, by enema, at a dose of 5 mL/kg, after allowing the feces to thaw at room temperature overnight prior to administration. After the first transfer, two other transfers were performed two days apart. After the third transfer, the last classification of fecal consistency was performed, observing whether there was clinical improvement. A telephone follow-up was then carried out with the owner to follow the evolution of the animal and the patient was summoned when it was considered appropriate. In the pharmacokinetic study of tylosin, 5 dogs were used, all of them healthy, neutered male Beagles weighing between 15.6 and 24 kg. The animals were between 2 and 3 years of age. The study was a 2-phase crossover study, with intervals between each phase of 15 days to ensure the absence of interference between each of the studies. The aforementioned antibiotic was administered at a dose of 5 mg/kg in aqueous solution intravenously (IV) in the right cephalic vein, and orally (PO) by administration of the weighed and individualized powder dose in capsules. Blood samples (1 mL) were collected from the left cephalic vein up to 24h from IV administration and up to 96 h from PO administration of the drug. Analytical determination of tylosin in plasma samples was performed by high performance liquid chromatography (HPLC), using the method of Abu-Basha et al. (2012), slightly modified. In the pharmacokinetic study of Infliximab, 5 dogs were used, which were administered by slow intravenous infusion, during 1'5 hours, a dose of 5 mg/kg, and were kept under hospitalized conditions, during the first 24 hours and then returned to their home kennels. To evaluate the tolerance of the dogs to the dose of infliximab administered, blood, hematological and biochemical analyses were performed. The analytical determination of infliximab in serum samples was performed using the Promitor IFX© kit (Grifols, Spain), a validated commercial enzyme-linked immunosorbent assay (ELISA) method. The pharmacokinetic study of tylosin and infliximab was performed by compartmental and non-compartmental analysis. Regarding the results obtained with FMT, the CIBDAI index showed a 100% clinical improvement after transplantation in both groups. In the case of the Walthan index, the improvement was also 100%. In addition, none of the animals suffered weight loss after treatment and, in case 2 of group 2, the patient not only regained his weight, but continued to increase it afterwards. All animals improved by decreasing stool frequency before and after FMT in group 1, while in group 2 all improved except one case. Another of the parameters that provide the most information on the success or otherwise of FMT is the evolution of stool consistency. In our study, the results have been quite positive, with 100% of the cases presenting an increase in stool consistency. The distribution of tylosin in dogs follows a bicompartmental model after intravenous administration of 5 mg/kg of the drug. The half-life of the fast disposition phase (t½λ1) for tylosin, has been 1.3 hours, and that of the slow disposition phase (t½λz) 8.89 hours and an MRT value of 10.07 hours has been obtained. The Cl obtained was 0.21 L/kg/h, the Vss acquired a value of 2.15 L/kg, while Vz reached a value of 2.77 L/kg. After administration of tylosin in oral formulation, a Ka of 2.11 h-1 and a t½ka of 0.33 h were obtained. The bioavailability obtained was 13.25±1.5%. As for infliximab, after IV infusion, its plasma concentrations conform to a monocompartmental model. Its t½λz was 210 hours and its MRT was 331 hours. It should be noted that the high half-life obtained, although shorter than in humans, would allow long dosing schedules of up to 6 weeks in the case that animals affected by inflammatory bowel disease can be treated. Its Cl has been 0.0001 L/kg/h, the Vss acquires a value of 0.049 L/kg and the Vz reaches a value of 0.047 L/kg. Regarding the tolerance of dogs to infliximab, no alteration in hematocrit or red blood cell count was observed, indicating no anemia and normal bone marrow function. There was no vitamin B or folic acid deficiency and no liver disorders are to be expected. The levels of leukocytes, segmented, lymphocytes, monocytes, eosinophils and basophils remain at all times within the limits admitted as normal. In the case of the biochemical parameters tested, all remain within the ranges accepted as normal during the whole experience. In conclusion, 100% of the animals with IBD treated with TMF obtained a clinical benefit. Analysis of the pharmacokinetic parameters for the two pathways tested for tylosin indicate a wide distribution (Vz = 2.77 L/kg) and sufficient for potential treatment of conditions in dogs with inflammatory bowel disease. The permanence of the drug infliximab in the dog, after its IV infusion, according to the plasma half-life obtained was 210 h (IV), may allow establishing dosage regimens sufficiently broad for the treatment of inflammatory intestinal processes.