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Canada (158,073)
Psychology (9,549)
PSYC62H3 (273)
Chapter 8

chapter 8

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University of Toronto Scarborough
Suzanne Erb

CHAPTER 8 pg 169-181 SEDATIVEHYPNOTICS AND ANXIOLYTICS Drugs with sedativehypnotic properties are perhaps the most commonly used and abused drugs in U.S. society, with alcohol topping the list. Despite the fact that they posses all the qualities that society deems unacceptable with respect to drugs (namely, toxicity, lethality, social disruptiveness, and psychological and physical dependence), and despite the fact that they are more destructive to individuals and society than all other drugs combined, they are readily accepted in both recreational and medicinal contexts. ~20% patients seen in psychiatric facilities are alcoholics. The term sedativehypnotic is used because, in most individuals, the lower doses of these drugs have psychological calming effect, and somewhat higher does have a hypnotic or sleep-inducing effect. These drugs are also commonly called CNS depressants, because their predominant tendency is to inhibit the excitability of neurons. Not all neurons decrease their rate of firing, particularly at the lower doses. In fact, while many neurons decrease their rate of firing with these drugs, others may increase their rate of firing because of the removal of the inhibitory influence of other neuronsan inhibition of inhibition or disinhibition. Alcohol (ethanol) is the most used and abused recreational sedative-hypnotic drugs in U.S. society, and barbiturates and benzodiazepines are among the most frequently abused prescription sedative-hypnotics. All of these drugs differ primarily in their quantitative aspectsthat is, the latency of onset, the intensity of effect, and the duration of actionwithout having any distinct qualitative differences. Their qualitative effects are directly dose related. Lower doses induce sedation; moderate doses induce sleep somewhat similar to natural sleep, in which the person is still responsive to pain; high doses induce sleep to the point of anaesthesia; and successively higher dose can cause coma, respiratory arrest and death. www.notesolution.com In the lower dose range, excitement, increase activity, pregariousness, and aggression may occur in some individuals. This phenomenon has commonly been attributed to the disruption of neural pathways of higher cortical origin that play an inhibitory function of subcortical centers of the brain= disinhibition. BARBITURATES AND OTHER SEDATIVEHYPNOTICS Barbiturates and other drugs in the sedativehypnotic class have effects so similar to alcohols effects, except to note that long-term alcohol exposure probably has more toxic physiological consequences. Sedative-hypnotic compounds without the barbiturate structure, such as methaqualone and glutethimide, have been synthesized, but their actions are essentially indistinguishable from those of the barbiturates. Barbiturates differ from each other primarily in terms of pharmacokinetics, which determines how quickly the drugs act, their intensity of action, and their duration of action. (all three properties are tied together) These differences in these properties are a major factor in determining what these drugs are used for. For example the ultrashort-duration ~15min is used as an anaesthetic, they can be used as sedative, sleep inducers and an anticonvulsant. Over the past 3 years the medical use of these drugs has declined considerably, primarily because of the development of newer compounds with less toxicity of dependence liability. They are no longer under patent, and thus they are very inexpensive. The general tendency of these drugs is to decrease the excitability of neurons throughout the nervous system. Although barbiturates depolarize some neurons, their predominant action throughout the nervous system is to hyperpolarize neurons. The inhibitory influence of barbiturates has been postulated to be due to their ability to enhance GABAs activity at the GABA A type receptor, which results in the opening of Cl- channels, allowing Cl- to slow into neurons and hyperpolarizing them. The primary action of barbiturates appears to be one of prolonging the duration that these channels remain open. www.notesolution.com
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