Kappa receptors agonist-antagonists/partial agonists

Opioid receptor binding Pentazocine (Brogden et al., 1973) is a mixed opioid agonist-antagonist with agonistic effects at the kappa and partial antagonistic effects at the p-type of opioid receptor. 

Buprenorphine hinds to mu, kappa, and delta opioid receptor suhtypes. It has a partial agonist activity at mu receptors and an antagonist activity at kappa receptors. Less is known about the activity of buprenorphine at delta receptors. Buprenorphine is more lipophilic than morphine and penetrates the blood-brain barrier more easily and has a rapid onset of effect. 

Major and minor sites of action methyinaltrexone is a peripheral opioid-receptor antagonist. It is also a partial agonist at mu, delta, and kappa opioid receptors. 

Buprenorphine is derived from thebaine. It is a partial mu agonist with kappa antagonist activity. Buprenorphine has 25 to 50 times the potency of morphine. It is used to produce a longer-lasting analgesia than morphine. Effects of buprenorphine last longer because it is released more slowly from mu receptors than morphine. It is available as an injectable for intramuscular (IM) or intravenous administration in a 1-ml solution containing 0.3 mg buprenorphine (as buprenorphine HC1) for the relief of moderate to severe pain. It is also available to treat opioid dependence in the formulation of a tablet,51 alone or in combination with naloxone, in 2- or 8-mg... 

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