Tolazoline

dose responses and side effects in non-sedated Holstein calves

Abstract

The objective of this study was to investigate the dose response effects of intravenous administration of tolazoline and to characterize the side effects associated with these doses in Holstein calves. Six healthy calves (mean body weight 352.7 ± 87.8 lb; 160.3 ± 39.9 kg) were used in the study. Seven doses (0.23, 0.45, 0.68, 0.91, 1.82, 3.64 and 4.55 mg/lb; 0.5, 1, 1.5, 2, 4, 8 and 10 mg/kg) of tolazoline administered intravenously via jugular vein were studied. Calves were allowed to recover over a period of seven days between each experiment. Heart rate, respiratory rate, mucous membrane color and capillary refill time were recorded before drug administration and at 10 minute intervals for 90 minutes after drug administration. Signs of adverse effects such as anxiety, excitement, CNS depression, salivation, bright red mucous membrane color, sweating, piloerection, trembling, hyperesthesia on the head and neck, muscle weakness, recumbency, dyspnea, abnormal breathing patterns, abdominal pain and diarrhea were recorded. At lower doses (≤0.68 mg/lb; 1.5 mg/kg), administration of tolazo-line caused coughing, increased frequency of defecation and mild increase in breathing effort. At higher doses (0.91-4.55 mg/lb; 2-10 mg/kg), adverse effects such as bright red conjunctival mucous membrane, coughing, nasal discharge, salivation, increased breathing effort (labored breathing), CNS depression, signs of abdominal pain, straining, head pressing, restlessness, increased frequency of defecation and diarrhea were observed. All calves recovered.