tailieunhanh - Color Atlas of Pharmacology (Part 21): Psychopharmacologicals

Psychopharmacologicals tive driving skills and other tasks requiring precise sensorimotor coordination will be impaired. Triazolam (t1/2 of elimination ~– h) is especially likely to impair memory (anterograde amnesia) and to cause rebound anxiety or insomnia and daytime confusion. The severity of these and other adverse reactions (., rage, violent hostility, hallucinations), and their increased frequency in the elderly, has led to curtailed or suspended use of triazolam in some countries (UK). Although benzodiazepines are well tolerated, the possibility of personality changes (nonchalance, paradoxical excitement) and the risk of physical dependence with chronic use must not be overlooked. . | 226 Psychopharmacologicals Benzodiazepines Benzodiazepines modify affective responses to sensory perceptions specifically they render a subject indifferent towards anxiogenic stimuli . anxiolytic action. Furthermore benzodiazepines exert sedating anticonvulsant and muscle-relaxant myotonolytic p. 182 effects. All these actions result from augmenting the activity of inhibitory neurons and are mediated by specific benzodiazepine receptors that form an integral part of the GABAA receptor-chloride channel complex. The inhibitory transmitter GABA acts to open the membrane chloride channels. Increased chloride conductance of the neuronal membrane effectively shortcircuits responses to depolarizing inputs. Benzodiazepine receptor agonists increase the affinity of GABA to its receptor. At a given concentration of GABA binding to the receptors will therefore be increased resulting in an augmented response. Excitability of the neurons is diminished. Therapeutic indications for benzodiazepines include anxiety states associated with neurotic phobic and depressive disorders or myocardial infarction decrease in cardiac stimulation due to anxiety insomnia preanesthetic preoperative medication epileptic seizures and hypertonia of skeletal musculature spasticity rigidity . Since GABA-ergic synapses are confined to neural tissues specific inhibition of central nervous functions can be achieved for instance there is little change in blood pressure heart rate and body temperature. The therapeutic index of benzodiazepines calculated with reference to the toxic dose producing respiratory depression is greater than 100 and thus exceeds that of barbiturates and other sedative-hypnotics by more than tenfold. Benzodiazepine intoxication can be treated with a specific antidote see below . Since benzodiazepines depress responsivity to external stimuli automo tive driving skills and other tasks requiring precise sensorimotor coordination will be impaired. Triazolam t1 2 of elimination .