Cyprenorphine

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Cyprenorphine is a powerful opioid drug related to buprenorphine and diprenorphine. It is extremely potent and mainly acts as an antagonist at opioid receptors, meaning it can block other opioids from working. It also has mixed agonist–antagonist effects like buprenorphine, but its stronger dysphoric and hallucinogenic effects make it less useful as a painkiller in humans.

Key points
- Potency and action: Very strong at blocking opioid receptors; can prevent effects of morphine and etorphine.
- Effects: Can cause pronounced dysphoria and hallucinatory experiences; this limits its use for pain relief in people.
- Behavior and testing: May suppress certain appetites in experiments and can increase general activity in some situations.
- Veterinary use: Used to reverse the immobilizing effects of etorphine in large animals. The reversal dose is usually about three times the initial etorphine dose. Etorphine is typically given by a dart into muscle, while cyprenorphine is given to rapidly reverse the effects, often by injection into a vein of the immobilized animal. The reversal process is generally quick, but can take longer in some species (e.g., white rhinoceroses).
- Availability: Etorphine and cyprenorphine are white powders that are often used together in field settings and cannot be purchased separately.
- Humans vs. animals: Because of side effects, cyprenorphine is rarely used in humans; diprenorphine is often preferred for reversing opioids in people.
- Related form: There is an isoform called 16-methyl cyprenorphine that blocks multiple opioid receptors (delta, mu, and kappa) and has its own specific receptor interactions.