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Pharmacokinetics of a New Parenteral Formulation of Tilmicosin-La in Cows
Lilia Gutiérrez1, Rodrigo Soriano1,  Ismael Martínez-Cortes2, Jorge Miranda-Calderon1 and Héctor Sumano1*
1Departamento de Fisiología y Farmacología and 2Departamento de Medicina en Rumiantes Facultad de Medicina Veterinaria y Zootecnia. Universidad Nacional Autónoma de México. Av. Universidad 3000, Delegación Coyoacán, Ciudad de México C.P. 04510, México
*Corresponding author: sumano@


The blood serum pharmacokinetics of a Poloxamer-407 based new pharmaceutical preparation of 39% tilmicosin was determined in cows.  Two dose levels injected SC, were assessed: 10 mg/kg (Til-LA10) and 26 mg/kg (Til-LA26). Tilmicosin was determined using HPLC, also electrocardiographic (EKG) monitoring in all animals before and at 1, 2 and 4 h after the injection of the drug was performed to measure key EKG parameters, including heart rate. Maximum serum concentration values were 2.6 µg/mL and 1.23 µg/mL, occurring 4.9 and 5.1 h after the injection of Til-LA26 and Til-LA10, respectively.  Mean residence time was statistically larger for Til-LA26 (50.4±5.8 h) than Til-LA10 (37.4±4.7 h) (P<0.05), with T½el of 39.8 h for Til-LA26 and 33.2 h for Til-LA10. There were no differences in relative bioavailability as adjusted for dose (AUMC of 8663 µg/mLžh2 for Til-LA26 and 2858 µg/mLžh2 for Til-LA10). This new formulation as dosed for Til-LA26 possesses a long T½el of tilmicosin and resulted in a lack of changes in the EKG and heart rate. Based on PK/PD ratios tilmicosin is regarded as a time-dependent antibacterial drug. Considering a theoretical minimum therapeutic serum concentration (MTC) of  0.1 µg/mL useful concentrations can be achieved for up to 192 h with Til-LA26 and an AUC/MTC ratio of 1514 without cardiac toxicity. Further studies are necessary to correlate PK/PD parameters obtained with clinical efficacy and a more thorough analysis of cardiac toxicity is required to determine the suitability of this preparation in bovine medicine.

Key words: Cow, Long-acting, New-preparation, Pharmacokinetics, Tilmicosin


ISSN 0253-8318 (Print)
ISSN 2074-7764 (Online)