Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2020 Publisher: Martindale Pharmaceuticals Ltd, Bampton Road, Romford, Essex, RM3 8UG, United Kingdom
Pharmacotherapeutic group: Drugs used in opioid dependence
ATC code: N07BC01
The Espranor oral lyophilisate dosage form is designed to rapidly disperse on the tongue usually in less than 15 seconds.
Buprenorphine is an opioid partial agonist/antagonist which attaches itself to the μ (mu) and κ (kappa) receptors of the brain. Its activity in opioid maintenance treatment is attributed to its slowly reversible link with the μ receptors which, over a prolonged period, minimises the need of the addicted patient for drugs.
During clinical pharmacological studies in opiate-dependent subjects, buprenorphine demonstrated a ceiling effect on a number of parameters, including positive mood, “good effect”, and respiratory depression.
When taken orally, buprenorphine undergoes first-pass hepatic metabolism with N-dealkylation and glucuroconjugation in the small intestine and liver. The use of this medication by the oral route is therefore inappropriate.
Peak plasma concentrations are achieved around 70 minutes after oromucosal administration and the maximal dose-concentration relationship is linear, between 2 mg and 8 mg.
The absorption of buprenorphine is followed by a rapid distribution phase and a distribution half-life of 2 to 5 hours.
Buprenorphine is metabolised by 14-N-dealkylation and glucuroconjugation of the parent molecule and the dealkylated metabolite. Clinical data confirm that CYP3A4 is responsible for the N-dealkylation of buprenorphine. N-dealkylbuprenorphine (also known as norbuprenorphine) is a μ (mu) agonist with weak intrinsic activity.
Elimination of buprenorphine is bi- or tri- exponential, and has a mean half-life from plasma of 32 hours.
Buprenorphine is eliminated in the faeces by biliary excretion of the glucuroconjugated metabolites (70%), the rest being eliminated in the urine.
Pre-clinical data reveal no special hazard for humans based on conventional studies of safety pharmacology, repeat dose toxicity, genotoxicity or carcinogenicity.
From teratology studies in rats and rabbits, it was concluded that buprenorphine is not embryotoxic or teratogenic, and it does not have any marked effects on weaning potential. There were no adverse effects on fertility or general reproductive function in rats, although at the highest intramuscular dose (5 mg/kg/day) the mothers experienced some difficulty in parturition and there was a high neonatal mortality.
Minimal to moderate hyperplasia of the bile duct with associated peribiliary fibrosis occurred in dogs following 52 weeks of oral dosing of 75 mg/kg/day.
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