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Pharmacology: Pharmacodynamics: Alprazolam, like other benzodiazepines, has a high affinity for the benzodiazepine binding site in the brain. It facilitates the inhibitory neurotransmitter action of gamma-aminobutyric acid which mediates both pre- and post-synaptic inhibition in the central nervous system (CNS).
Pharmacokinetics: Following oral administration, peak plasma concentrations are reached in about 1.7 hours. After a single oral dose of 500 micrograms, the average maximal concentration was 7.1 nanograms/ml. There is a linear relationship between the dose and plasma concentration. At least 80% of the oral dose is absorbed. About 70% of the absorbed dose is bound to plasma proteins.
Alprazolam is extensively metabolised in the liver, primarily to hydroxylated metabolites, but about 20% of the dose is excreted as unchanged alprazolam. Elimination occurs mostly via the kidneys; 80% of the dose is excreted into the urine and only 7% into the faeces. The mean elimination half-life is 10-12 hours.
