Pharmacology
Pharmacodynamics
Opioid receptor modulator
Buprenorphine has been reported to possess these following pharmacological activities:
μ-Opioid receptor (MOR): Very high affinity partial agonist: at low doses, the MOR-mediated effects of buprenorphine are comparable to those of other narcotics, but these effects reach a "ceiling" as the receptor population is saturated. This behavior is responsible for several unique properties: buprenorphine greatly reduces the effect of most other MOR agonists, can cause precipitated withdrawal when used in actively opioid dependent persons, and has a lower incidence of respiratory depression and fatal overdose relative to full MOR agonists. κ-Opioid receptor (KOR): High affinity antagonist—this activity is hypothesized to underlie some of the effects of buprenorphine on mood disorders and addiction. δ-Opioid receptor (DOR): High affinity antagonist
Nociceptin receptor (NOP, ORL-1): Weak affinity, very weak partial agonistIn simplified terms, buprenorphine can essentially be thought of as a nonselective, mixed agonist–antagonist opioid receptor modulator, acting as an unusually high affinity weak partial agonist of the MOR, a high affinity antagonist of the KOR and DOR, and a relatively low affinity, very weak partial agonist of the ORL-1/NOP.Although buprenorphine is a partial agonist of the MOR, human studies have found that it acts like a full agonist with respect to analgesia in opioid-intolerant individuals.
Adverse effects
Common adverse drug reactions associated with the use of buprenorphine, similar to those of other opioids, include nausea and vomiting, drowsiness, dizziness, headache, memory loss, cognitive and neural inhibition, perspiration, itchiness, dry mouth, shrinking of the pupils of the eyes (miosis), orthostatic hypotension, male ejaculatory difficulty, decreased libido, and urinary retention. Constipation and central nervous system (CNS) effects are seen less frequently than with morphine. Respiratory effects
The most severe side effect associated with buprenorphine is respiratory depression (insufficient breathing). It occurs more often in those who are also taking benzodiazepines or alcohol, or have underlying lung disease. The usual reversal agents for opioids, such as naloxone, may be only partially effective, and additional efforts to support breathing may be required. Respiratory depression may be less than with other opioids, particularly with chronic use. In the setting of acute pain management, though, buprenorphine appears to cause the same rate of respiratory depression as other opioids such as morphine. Buprenorphine dependence
Buprenorphine treatment carries the risk of causing psychological or physiological (physical) dependencies. It has a slow onset of activity, with a long duration of action, and a long half-life of 24 to 60 hours. Once a patient has stabilised on the (buprenorphine) medication and programme, three options remain - continual use (buprenorphine-only medication), switching to a buprenorphine/naloxone combination, or a medically supervised withdrawal. Pain management
Achieving acute opioid analgesia is difficult in persons using buprenorphine for pain management.