Partial agonist buprenorphine is an opioid, which strikingly differs chemically from other opioids, in that it is not related to morphine, but to another alkaloid called thebaine.
So buprenorphine is a semi synthetic opioid.
Pharmacodynamically, partial agonist buprenorphine is highly potent. 0.3 mg is equianalgesic with 10 mg of morphine. It has a 50 times greater affinity than that of morphine.
As a result, the respiratory depression produced by this drug is very prolonged, and being non-related to antagonists (which are structurally related to morphine), in therapeutic doses naloxone cannot reverse its actions.
For this purpose, to reverse the effect of this drug on respiratory depression, general CNS stimulant like doxapram is needed. Sedation and drowsiness which is not so common in pure agonists is commonly seen (in 50% of the patients). In addition, contrary to pure agonists, nausea and vomiting may be seen in only 10—20 % of the patients.
The other significant feature differentiating partial agonist buprenorphine from pure agonists is it has the capability of reversing respiratory depressant effects of pure agonists.
Partial agonist buprenorphine differs from agonists-antagonists in that it does not produce psychomimetic, dysphoriant effects like these drugs.
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