Drug delivery techniques are an integral component in modern medical practices. Numerous drugs have been designed to exploit drug delivery systems, primarily oral administration, as it is preferred by the public for treatment of animals and humans. Butorphanol is a commonly used opioid analgesic drug for pain relief in avian species. The pharmacokinetic reports on butorphanol suggest that it is metabolised and cleared from an avian body at a much faster rate when compared to mammals. A single intravenous injection of butorphanol at 2 mg/kg provides analgesia for only 2 hours. When given at higher doses, butorphanol starts to produce side effects such as hyperventilation, cardiac insufficiency, coma and death. Therefore, there is a need to develop a slow release drug delivery system for butorphanol which can prolong the duration of analgesia without the side effects.
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