Reversal of oxymorphone sedation by naloxone, nalmefene, and butorphanol

The effects of naloxone (0.4 mg and 1.2 mg intravenously [IV]), nalmefene (0.03 mg/kg IV) and butorphanol (0.2 mg/kg IV and 0.4 mg/kg IV) on oxymorphone-induced sedation were studied in six dogs over a 4-hour observation period. The same dogs were observed for 4 hours untreated (unsedated control) and with oxymorphone sedation followed by saline solution (sedated control). The reversal drug or saline placebo was administered IV 20 minutes after oxymorphone (4.5 mg IV). Blinded observers evaluated the dogs for positional and attitudinal responses, heart rate, and respiratory rate. Sedated dogs treated with nalmefene most closely resembled unsedated dogs in all observed variables. Naloxone was most effective when administered at the higher dose. Mild renarcotization occurred in two dogs at hour 2, even after the higher naloxone dose. Residual sedation was observed in all dogs treated with 0.4 mg naloxone. Butorphanol resulted in partial reversal of sedation at both dosage levels. However, the degree of sedation was significantly less than that observed in the saline-treated controls, and it appeared that 0.4 mg/kg butorphanol may be clinically useful for opiate reversal in some situations.