Buprenex

Buprenorphine, also colloquially referred to as bupe, is an opioid drug with partial agonist and antagonist actions. Buprenorphine hydrochloride was first marketed in the 1980s by Reckitt & Colman (now Reckitt Benckiser) as an analgesic, yet is now primarily used for the treatment of opioid addiction. It is a Schedule III drug under the Convention on Psychotropic Substances. more...

Commercial preparations

Britsh firm Reckitt & Colman (now Reckitt Benckiser) first marketed buprenorphine under the trade names Temgesic (sublingual/parenteral preparations, no active additives) and Buprenex (parenteral, no active additives). Two more recent formulations from Reckitt Benckiser have been approved for opioid addiction treatment in the U.S.: Subutex (lemon-lime flavored sublingual, no active additives; in 2mg and 8mg dosages) and Suboxone (orange-tang flavored sublingual, one part naloxone for every four parts buprenorphine; hexagon shaped tablet in 2mg and 8mg dosages). Suboxone contains the opioid antagonist naloxone to deter illicit intravenous preparation of the tablet, this is intended to attenuate the effects of buprenorphine on opioid-naive users should this formulation be injected - however no human studies have been done demonstrating the efficacy of this approach with buprenorphine and a growing number of street reports indicate that the naloxone is ineffective. It must also be noted that buprenorphine in and of itself will induce a precipitated withdrawal syndrome if ingested by an acutely opioid dependent individual via any route.

Buprenorphine is also delivered transdermally in 25, 50 and 75 mcg/hour. The trade name in the UK is Transtec, and manufactured by Napp. A new 5, 10 and 20 mcg/hour patch marketed as Bu'7rans (Bu-trans), where the 7 indicates its once weekly dosage for pain in osteoarthritis.

Pharmacology and pharmacokinetics

Buprenorphine is a thebaine derivative, and its analgesic effect is due to partial agonist activity at μ-opioid receptors. The partial agonist activity means that opioid receptor antagonists (e.g. naloxone) only partially reverse the effects of buprenorphine. Buprenorphine is also a κ-opioid receptor partial agonist/antagonist, and partial/full agonist at the recombinant human ORL1 nociceptin receptor. (Huang et al., 2001)

Buprenorphine hydrochloride is administered by intramuscular injection, intravenous infusion, via a transdermal patch, or as a sublingual tablet. It is not administered orally, due to very high first-pass metabolism. Buprenorphine is metabolised by the liver, via the CYP3A4 isozyme of the cytochrome p450 enzyme system, into norbuprenorphine (by N-dealkylation) and other metabolites. The metabolites are further conjugated with glucuronic acid and eliminated mainly through excretion into the bile. The elimination half-life of buprenorphine is 20.4–72.9 hours (mean 34.6).

The main active metabolite, norbuprenorphine, is a δ-opioid receptor and ORL1 receptor agonist, μ- and κ-opioid receptor partial agonist. (Huang et al., 2001)

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