Analgesic effects of butorphanol in horses: dose-response studies.

This research investigates the pain-relieving effects of a drug called butorphanol in horses. Results suggest that the potency and duration of analgesia from butorphanol are dose-related, and this drug possesses a stronger effect than the comparator, pentazocine.

Experimental Design and Methodology

• This experiment was conducted on 6 horses that were set up to objectively measure their response to painful superficial and visceral stimuli.
• The drugs tested in the experiment were different dosages of butorphanol (0.05, 0.1, 0.2, and 0.4 mg/kg), pentazocine (2.2 mg/kg), and a butorphanol vehicle (0.04 ml/kg).
• The Latin square design was utilized in administering the drugs intravenously to the horses. This design is used when researchers want to ensure that a variable does not impact the results adversely due to an ordering effect.
• Before the drugs were injected, baseline measurements were established. Then, the post-injection analgesic effects were observed at 15, and 30 minutes, and subsequently every 30-minute intervals until minute 240.

Findings

• The research found that the pain-relieving effects of butorphanol were dose-dependent – the higher the dosage, the stronger and longer the analgesic effects were. Specifically, the effects of the different butorphanol doses lasted between 15 and 90 minutes.
• When pentazocine was administered at a dosage of 2.2 mg/kg, the duration of its analgesic effect ranged from 15 to 30 minutes.
• When compared with pentazocine, the highest tested dose of butorphanol (0.4 mg/kg) provided a more intense and more extended period of analgesia.
• The researchers proposed the optimal dose of butorphanol to be 0.2 mg/kg when injected intravenously.
• On comparing the potencies, the researchers found that butorphanol was 10 to 17 times more potent than pentazocine, when dosage and body weight were considered.
• Both drugs had behavioral side effects on the horses, with these effects increasing with dosage.

Implications and Conclusion

• The results of this study provide important insights into the dose-response relationship of butorphanol. The effectiveness and duration of its analgesic effects were found to be clearly dose-related.
• The study’s findings suggest that butorphanal could potentially be a more efficient choice of analgesic than pentazocine in horses, given its superior potency and duration.
• The determination of the optimal dose of butorphanol (0.2 mg/kg) could serve to guide its usage in veterinary practice, striking a balance between its analgesic effects and side effects.