5,5-Barbiturates, hypnosis

Shah HC, Lal H. 1976. Effects of 1,1.1-trichloroethane administered by different routes and in different solvents on barbiturate hypnosis and metabolism in mice. J Toxicol Environ Health 1 807-816. 

Certain pharmacologic actions of chlorpromazine have also been associated with central catecholamine function. Reduction of brain catecholamine levels in rats by inhibition of tyrosine hydroxylation enhanced the usual chlorpromazine-induced effects of hypothermia, potentiation of barbiturate hypnosis and blockade of a conditioned avoidance responsel That conditioned avoidance responses are dependent upon the activation of central catecholamine neurons has been demonstrated by histochemical and pharmacologic studies - ... 

All barbiturates have essentially die same mode of action. Depending on the dose given, tiiese drags are capable of producing central nervous system (CNS) depression and mood alteration ranging from mild excitation to mild sedation, hypnosis (sleep), and deep coma These drugs also are respiratory depressants the degree of depression... 

Sedation is an intermediate degree of CNS depression, while hypnosis is a degree of CNS depression similar to natural sleep. From the chemical point of view, soporific, sedative, and hypnotic drugs are classified as barbiturates, benzodiazepine hypnotics, and so on. Except for a few rare exceptions, any one of these compounds can be used for acquiring a sedative effect or state of sleep. Presently, the less toxic benzodiazepines are edging out the class of barbiturates more and more because of the possibility of chronic dependence associated with the use of barbiturates. Drugs of both classes are primarily CNS depressants, and a few of their effects, if not all, are evidently linked to action on the GABA-receptor complex. 

Pharmacology These agents depress the sensory cortex, decrease motor activity, alter cerebellar function, and produce drowsiness, sedation, and hypnosis. Barbiturates have little analgesic action at subanesthetic doses and may increase the reaction to painful stimuli. All barbiturates exhibit anticonvulsant activity in anesthetic doses. However, only phenobarbital and mephobarbital are effective as oral anticonvulsants in subhypnotic doses. 

Barbiturates are the derivatives of barbituric acid. They are general CNS depressants. They can cause sedation, hypnosis and general anaesthesia depending upon the particular barbiturates used and its dose. 

Barbiturates are referred to as sedative-hypnotics. These drugs will induce sleep which can lead to even deeper sedation (hypnosis) and can cause a fatal depression of the RAS affecting the respiratory system. The sleep which is encountered does not have the normal cycles of slow wave and rapid eye movement activity, so it is not always restful. However, these agents prove to be useful in anesthesia for both short and longer durations of time. Many of you may have been given thiopental prior to wisdom tooth extraction. Thiopental "wears off quickly and so the actual anesthetic for the time of the extraction is usually nitrous oxide. 

Actions Phenytoin is not a generalized CNS depressant like the barbiturates, but it does produce some degree of drowsiness and lethargy without progression to hypnosis. Phenytoin reduces the propagation of abnormal impulses in the brain. 

The barbitmates are the other major group of sedative-hypnotic agents. Similar to the benzodiazepines, they are a group of chemically related drugs and there are many variations in properties, particularly onset of effects and duration of action. The most recognized effects of the barbiturates are centrally mediated and include sedation, hypnosis, decreased anxiety, and, at high doses, anesthetic properties. The mechanism of... 

Some of the more frequently used barbiturates are described briefly in the following sections. For the structures, the usual dosages required to produce sedation and hypnosis, the times of onset, and the duration of action, see Table 14-2,... 

Mephobarbital is a barbiturate sedative and hypnotic agent. It depresses sensory cortex, decreases motor activity, alters cerebellar fnnction, and produces drowsiness, sedation, and hypnosis. It is indicated as a sedative for relief of anxiety, tension, and apprehension and as an anticonvnlsant for the treatment of grand mat epilepsy. 

Most barbiturates have antiseizure properties. The discussion below is limited to the two barbiturates that exert maximal antiseizure action at doses below those required for hypnosis, a property that determines their clinical utility as antiseizure agents. The pharmacology of barbiturates is considered in Chapter 16. 

In general, the barbiturates exert a significant depressant action on the cerebrospinal axis. The relative degrees of depression, sedation, hypnosis or anaesthesia are exelusively dependent on the nature of the barbiturate, its dose and route of administration. 

It is a barbiturate of choice for rapid action, administered intravenously, for causing anaesthesia, supplementing general anaesthetic agents, short surgical trauma and induction of hypnosis. 

Barbiturates are derivatives of barbituric acid. These substances were once used extensively in clinical practices as sedatives-hynotics. Because of their abuse and physical dependence, their therapeutic application has diminished considerably. The sedative effects of barbiturates are similar to those of alcohol. Higher dosage can cause hypnosis and anesthesia. An intake of barbiturates 10-15 times that of the hypnotic dose can be toxic. Coma and death can result from overdose. 

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