Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2018 Publisher: Actavis UK Limited (Trading style: Actavis), Whiddon Valley, BARNSTAPLE, N Devon EX32 8NS
Pharmacotherapeutic group: Benzodiazepine derivatives
ATC code: N05BA01
Diazepam is a benzodiazepine tranquilliser with anticonvulsant, sedative, muscle relaxant and amnesic properties.
Benzodiazepines, such as diazepam, bind to receptors in various regions of the brain and spinal cord. This binding increases the inhibitory effects of gamma-aminobutyric acid (GABA). GABAs functions include CNS involvement in sleep induction. Also involved in the control of hypnosis, memory, anxiety, epilepsy and neuronal excitability.
Diazepam is readily and completely absorbed from the GI tract. Peak plasma concentrations occurring within about 30-90 minutes of oral administration, a steady plasma concentration is reached after 5-6 days and is directly related to dose.
Diazepam crosses the blood-brain barrier and is highly lipid soluble, this causes the initial effects to decrease rapidly as it is redistributed into fat deposits and tissues Diazepam is very extensively bound to plasma proteins (98-99%). Diazepam and its metabolites also enters breast milk and crosses the placenta freely, this may lead to accumulation in the infant or foetus.
Diazepam is extensively metabolised in the liver and, in addition to desmethyldiazepam, its active metabolites include oxazepam and temazepam. Diazepam has a biphasic half-life with an initial rapid distribution phase followed by a prolonged terminal elimination phase of 1 or 2 days; its action is further prolonged by the even longer half-life of 2-5 days of its principle active metabolite, desmethyldiazepam (nordiazepam), the relative proportion of which increases in the body on long-term administration. The plasma half-life of diazepam is prolonged in neonates, in the elderly, and in patients with kidney or liver disease.
It is excreted in the urine, mainly in the form of its metabolites, either free or in conjugated form.
Not applicable.
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