Pharmacokinetics and pharmacodynamics of two in-feed chlortetracycline regimens provided to beef cattle.

Plasma chlortetracycline (CTC) concentration data were subjected to Monte Carlo simulation of area under the concentration curve (AUC) values related to bovine respiratory disease pathogen MIC distributions to evaluate target attainment rates. Crossbred Hereford heifers were randomly assigned into two treatment groups. Treatment group (A) received chlortetracycline (CTC) at a target dose of 22 mg/kg of bodyweight daily for 5 consecutive days (n = 8) and group (B) received CTC at 350 mg/head per day (1.5 ± 0.2 mg/kg based on actual bodyweights) for seven consecutive days (n = 8). Non-compartmental analysis was used to calculate plasma-free drug CTC area under the concentration curves. The mean observed (±SD) free drug AUC values were 4.18 (±1.72) µg × h/mL and 0.30 (±0.06) µg × h/mL for treatment groups A and B, respectively. The probability of target attainment for AUC24/MIC values of 25 and 12.5 was modeled using Monte Carlo simulations. Treatment group A achieved >90% target attainment (AUC24/MIC of 25) at an MIC of 0.06 µg/mL, whereas treatment group B displayed only 12.6% target attainment (AUC24/MIC of 12.5) at the lowest MIC evaluated (0.015 µg/mL). Both in-feed CTC regimens failed to obtain a reasonable target attainment rate in light of expected MIC distributions of potential pathogens.

Pharmacokinetic report: Pharmacokinetics of a single oral dose of gabapentin in goats (Capra hircus).

Gabapentin is used in goats to treat chronic pain associated with lameness. However, pharmacokinetic data and clinical effectiveness trials are lacking. The objective of the study was to describe the pharmacokinetics of gabapentin in goats following a single oral dose. Six Spanish-crossbred goats were enrolled. Each goat was administered gabapentin at a target dose of 15 mg/kg per os. Serial blood samples were collected out to 60 h post-gabapentin administration for plasma gabapentin concentration determination. Plasma samples were analyzed for gabapentin concentration using ultra-high-pressure liquid chromatography coupled with mass spectroscopy. Individual animal pharmacokinetic outcomes were determined using non-compartmental analysis. Gabapentin was detectable in the plasma of all goats at 60 h post-administration. The mean (±SD) Cmax was 2.01 ± 0.62 µg/mL which occurred at 8.47 ± 1.9 h. The mean terminal half-life (T1/2) and mean resident time were determined to be 8.52 ± 1.8 and 18.7 ± 4.0 h, respectively. This study indicates gabapentin is absorbed from the gastrointestinal tract of goats. Further research is needed to determine an optimal dose for clinical efficacy in goats.