CNS depressants barbiturates

Diffutin (see above) has pronounced adaptogenic (anti-stress and anti-anxiety) activity, as well as being a mild CNS depressant (barbiturate potentiation). It also has a marked inotropic effect in perfused frog heart, and shows no arrhythmogenic properties. In addition, it potentiates the contractile response of guinea pig vas deferens to catecholamines, without inhibition of the uptake of adrenalin. At 500 mg/kg, diffutin is nontoxic to dogs. The use of Canscora in Indian medicine as a herbal remedy for certain mental disorders is supported by these observations. 

Benzodiazepiaes have largely replaced barbiturates and barbiturate-like agents for use as anxiolytics and sedative—hypnotics. Because benzodiazepiaes rarely produce levels of CNS depression that require therapeutic iatervention, the need for analeptics has decreased considerably. 

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... 

Because narcoticanalgesicsdepressthe CNS(see Chap. 19), the nurse should not administer a barbiturate or miscellaneous sedativesand hypnoticsapproximately 2 hoursbefore or after administration of a narcoticanalgesic or other CNS depressant. If the time interval between administration of a narcotic analgesic and a sedative or hypnotic is less than 2 hours the patient may experien ce severe respiratory depres-son, bradycardia, and unresponsiveness. 

The barbiturates are contraindicated in patients with known hypersensitivity to the drugs. The barbiturates are used cautiously in patients with liver or kidney disease and those with neurological disorders. The barbiturates (eg, phenobarbital) are used with caution in patients with pulmonary disease and in hyperactive children. When barbiturates are used with other CNS depressants (eg, alcohol, narcotic analgesics, and antidepressants), an additive CNS depressant effect may occur. See Chapter 26 for additional information on the barbiturates. 

Barbiturates produce CNS depression, which ranges from sedation to general anesthesia. Action is through suppression of the mesencephalic reticular activating system. Barbiturates enhance GABA-induced inhibition the site of inhibition may be presynaptic in the spinal cord or postsynaptic in the cortical... 

Death from overdose of barbiturates may occur and is more likely when more than 10 times the hypnotic dose is ingested. The barbiturates with high lipid solubility and short half-lives are the most toxic. Thus the lethal dose of phenobarbital is 6—10 g, whereas that of secobarbital, pentobarbital, or amo-barbital is 2-3 g. Symptoms of barbiturate poisoning include CNS depression, coma, depressed reflex activity, a positive Babinski reflex, contracted pupils (with hypoxia there may be paralytic dilation), altered respiration, hypothermia, depressed cardiac function, hypotension, shock, pulmonary complications, and renal failure. 

There are similarities between the biological actions of inhalants and those of alcohol and barbiturates (Bowen et al. 1996b). For example, acute administration of inhalants affects motor coordination (Moser and Balster 1981) and induces anxiolysis, whereas chronic administration is associated with physical dependence and withdrawal (Bowen et al. 1996a Evans and Balster 1991, 1993). In addition, some inhalant drugs have anticonvulsant properties (Wood et al. 1984). Like other CNS-depressant agents, inhalants have biphasic effects on spontaneous locomotor activity in rodents, with increased activity seen at lower doses and diminished locomotion seen at higher doses (Cause et al. 1985 Kjellstrand et al. 1985). 

Although PCP was developed as an anesthetic, its profile as an anesthetic is very different from typical general anesthetics of the CNS-depressant class (Domino 1964). Nonetheless, PCP has a number of behavioral and pharmacological effects similar to those of depressants such as the barbiturates (Balster and Wessinger 1983). PCP has profound motor effects, as evidenced by effects on rotorod performance and similar measures (Kalir et al. 1969 ... 

Withdrawal of CNS depressants (abrupt) Alcohol, barbiturates, benzodiazepines... 

CNS depressants (e.g., barbiturates, narcotics, benzodiazepines, short-term use of large doses of alcohol)... 

Several pharmacological issues pertain to most CNS depressant drugs (Hobbs et al. 1996 Julien 1997). Depending on their pharmacological mechanisms, combinations of CNS depressants can produce additive or synergistic effects, when the total effect is equal to or greater than the sum of their individual effects, respectively. For example, in doses that would be safe individually, combinations of alcohol and barbiturates can be lethal. 

Many CNS depressants have some liability for dependence. This is typically greater with barbiturates, but lesser with benzodiazepines, and perhaps nonexistent in many antiseizure medications. CNS depressants produce tolerance when administered chronically, where increasingly larger doses are required to sustain the same level of effect. Further, a cross-tolerance often develops, where the tolerance is generalized to other CNS depressants. For example, a person with an ethanol tolerance will also display some tolerance to barbiturates. The therapeutic index tends to decrease as tolerance increases, so that the difference between an effective and toxic dose diminishes. Thus, tolerance to CNS depressants is accompanied by a smaller safety margin. 

No health hazards are known with the proper use of kava (Gruenwald et al. 1998). Kava has been approved by the German Commission E for treatment of anxiety and insomnia. In clinical studies of kava for anxiety, adverse effects were uncommon and did not differ across placebo and kava groups. There do not appear to be any studies published on the effects of acute overdosage with kava. Given its CNS depressant effects, it should not be taken with other similar drugs, including benzodiazepines, barbiturates. 

Behaviorai effects Opioids produce sedation, but not as profoundly as CNS depressants like barbiturates or general anesthetics. A person administered an opioid is generally lethargic but arousable. 

Alkyl and 1-aralkyl-5,6-dihydrouracils (LXXIX), prepared by condensation of A -(2-carbamoylalkyl)aralkylamines with urea or by treating a suitable primary amine with an ester of acrylic acid followed by cyanic acid, are CNS depressants and anticonvulsants [639, 640], as well as anti-inflammatory agents [641]. Such compounds are to be compared with the corresponding barbituric acid derivatives in which not more than one hydrogen in the 5-position is substituted, and also with barbiturates in which the 5,5-substituents are similar to the R and groups of the 5,6-positions here. 

The discovery of the sedative/hynoptic activity of derivatives of barbituric acid has led to very extensive dissections of that molecule. One outcome of this work is the realization that acylurea and acylamide derivatives often exhibit CNS depressant activity. A fair number of such molecules have been prepared that contain a succinimide or glutarimide pharmacophore. For example, Michael addition of cyanide to the stereochemically xmdefined cinnamate... 

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. 

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