Intravenous administration of tramadol hydrochloride in sheep: a haematological and biochemical study

Tramadol is a synthetic, centrally acting opioid analgesic. This drug is a μ-opioid agonist that also inhibits the reuptake of noradrenaline and serotonin. The present study was carried out to investigate the effects of this drug on blood profile, hepatic enzymes activities and blood urea nitrogen (BUN) in sheep. For this purpose, ten healthy non-pregnant Lory ewes were used. Before the experiment, three blood samples were taken from the jugular vein as a control; ewes were then randomly divided into two groups. The test group was given tramadol IV (5 mg/kg) for five consecutive days; group 2, the sham group, was given normal saline IV (5 mg/kg) for the same time period. The results of present study showed that short-term injection of tramadol causes significant change in red blood cell count and packed cell volume value. However, level of serum activities of hepatic enzymes and BUN remained unaltered. In conclusion, these results suggest that although short-term use of tramadol may have no toxic effects on the liver and kidney, its effects on the blood profile should be kept in mind.