Gastrointestinal system benzodiazepines

Buspirone causes less psychomotor impairment than diazepam and does not affect driving skills. The drug does not potentiate the central nervous system depressant effects of conventional sedative-hypnotic drugs, ethanol, or tricyclic antidepressants, and elderly patients do not appear to be more sensitive to its actions. Tachycardia, palpitations, nervousness, gastrointestinal distress, and paresthesias may occur more frequently than with benzodiazepines. Buspirone also causes a dose-dependent pupillary constriction. Blood pressure may be elevated in patients receiving MAO inhibitors. A number of buspirone analogs have been developed (eg, ipsapirone, gepirone, tandospirone) and are under study. 

Absorption. The rate of absorption from the gastrointestinal tract after oral dosage determines the speed of the onset of action of a benzodiazepine. For a quick onset of action, the benzodiazepine must dissolve completely in the stomach and cross the stomach mucosa into the systemic circulation. The different dissolution and absorption kinetics of benzodiazepines will affect their onset of action. Once the benzodiazepine is in the systemic circulation, it must also cross the blood-brain barrier to enter the CNS. Therefore, the lipophilidty of the benzodiazepine is important in determining the entry into the CNS and the onset of clinical action. Most benzodiazepines are highly lipophilic with the 3-hydroxy-substi-tuted benzodiazepines (lormetazepam, loraz-epam, temazepam, and doxefazepam) triazolam is the least lipophilic. 

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