Substitution and primary dependence studies in animals.

Area of Science:

• Pharmacology
• Neuroscience
• Addiction Research

Background:

• Opioid analgesics are crucial for pain management.
• Understanding the dependence liability of mixed agonist-antagonist opioids is essential for clinical safety.
• Rhesus monkeys serve as a valuable model for studying opioid effects and addiction.

Purpose of the Study:

• To compare the pharmacological profiles of several mixed agonist-antagonist analgesics.
• To evaluate their potential for physical dependence and addiction.
• To differentiate their effects from prototype mu and kappa agonists.

Main Methods:

• Acute administration and behavioral observation in drug-naive rhesus monkeys.
• Discriminative stimulus studies using etorphine or ethylketazocine trained monkeys.
• Self-administration assays relative to codeine.
• Suppression and precipitation of withdrawal in morphine-dependent monkeys.
• Primary addiction studies in drug-naive animals.

Main Results:

• Buprenorphine and nalbuphine precipitated withdrawal in morphine-dependent monkeys.
• Chronic buprenorphine administration led to no observable abstinence signs, unlike nalbuphine.
• Butorphanol, pentazocine, and picenadol produced mild kappa-type dependence, mimicking Mr 2033 withdrawal.

Conclusions:

• Mixed agonist-antagonist analgesics exhibit varied physical dependence and addiction potential.
• Buprenorphine demonstrates a unique withdrawal profile with potential for reduced abstinence symptoms after chronic use.
• Kappa-type dependence was observed for butorphanol, pentazocine, and picenadol, differentiating them from mu agonists.