Pharmacology, barbiturates

Pharmacological Profiles of Anxiolytics and Sedative—Hypnotics. Historically, chemotherapy of anxiety and sleep disorders rehed on a wide variety of natural products such as opiates, alcohol, cannabis, and kawa pyrones. Use of various bromides and chloral derivatives ia these medical iadications enjoyed considerable popularity early ia the twentieth century. Upon the discovery of barbiturates, numerous synthetic compounds rapidly became available for the treatment of anxiety and insomnia. As of this writing barbiturates are ia use primarily as iajectable general anesthetics (qv) and as antiepileptics. These agents have been largely replaced as treatment for anxiety and sleep disorders. 

Authors are designed row sensitive and selective test-systems for analysis of heavy metals, active chlorine, phenols, nitrates, nitrites, phosphate etc. for analysis of objects of an environment and for control of ions Ee contents in the technological solutions of KH PO, as well as for testing some of pharmacological psychotropic daigs alkaloids (including opiates), cannabis as well as pharmaceutical preparations of phenothiazines, barbiturates and 1,4-benzodiazepines series too. 

The continuing search for molecules that possess the sedative-hypnotic properties of the barbiturates but show a better pharmacologic ratio has, as shown above, taken many directions. To name only two variants, the ring has been contracted and even opened entirely in each case some activity of the parent was retained. Although at one time the acylurea functional array was thought necessary for activity, the work below shows that even... 

Charney et al. (2001), Harvey (1985), Matthew (1971), and Wesson and Smith (1977) have discussed the pharmacology of barbiturates. Barbiturates are derived from barbituric acid, which is the product of the fusion of malonic acid and urea. Barbituric acid lacks CNS activity. The two main classes of barbiturates are the highly lipid-soluble thiobarbiturates, in which sulfur replaces oxygen at the second carbon atom of the barbituric acid ring, and the less soluble oxybarbiturates, with oxygen at the second carbon atom (Table 3-3). Highly lipid-soluble barbiturates have a more rapid onset, a short duration of action, and greater potency than those with lower lipid solubility. 

Barbiturates are rare these days but these depressants produce their pharmacological effects by increasing the duration of CU channel opening associated with GABAa receptors (see Chapter 11). 

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 ... 

A nonaqueous solvent or a mixed aqueous/nonaqu-eous solvent system may be necessary to stabilize drugs, such as the barbiturates, that are readily hydrolyzed by water, or to improve solubility (e.g., di-gitoxin). Nonaqueous solvents must be carefully screened and tested to ensure that they exhibit no pharmacological action, are nontoxic and nonirritating, and are compatible and stable with all ingredients of a formulation. 

Haefely WE (1977). Synaptic pharmacology of barbiturates and benzodiazepines. Agents Actions, 7(3), 353-359. 

Secobarbital exhibits the same pharmacologic properties as other members of the barbiturate class. Most nonmedical use is with short-acting barbiturates, such as secobarbital. Although there may be considerable tolerance to the sedative and intoxicating effects of the drug, the lethal dose is not much greater in addicted than in normal persons. Tolerance does not develop to the respiratory effect. The combination of alcohol and barbiturates may lead to fatalities because of their combined respiratory depressive effects. Similar outcomes may occur with the benzodiazepines. Severe withdrawal symptoms in epileptic patients may include grand mal seizures and delirium. 

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. 

The pharmacological activity of a series of 3,5,6-trialkyluracils was studied, considering them as analogues ofbarbitone, and it was found that they did possess sedative action. The 3,5-dibutyl-6-methyl derivative (XLVlll) was reported to be a comparatively potent sedative agent [372]. Partition coefficient and metabolic studies would be of interest in comparing such compounds with the barbiturates. 

The preparation of barbiturates illustrates many of the synthetic methods covered in this chapter. The preparation employs the reaction of urea (C0(NH2)2) with malonic ester to form barbituric acid. The general reaction is presented in Figure 15-30. The stable pyrimidine and other resonance forms help drive the reaction. By alternating the substituent at carbon number five (C5), various pharmacologically active substances can be formed. Barbital, a sedative, and phenobarbital, a sleeping aid, are shown in Figure 15-31. 

As with all of the examined drugs in this chapter, methyprylon is intended for treating insomnia. The pharmacological effects of methyprylon are similar to those of barbiturates. However, barbiturates are beginning to give way, thanks to the introduction of benzodiazepines into medical practice. Synonyms for this drug are noctar, noludar, and others. 

Pharmacology Zolpidem is a nonbenzodiazepine hypnotic. While zolpidem is a hypnotic agent with a chemical structure unrelated to benzodiazepines, barbiturates, or other drugs with known hypnotic properties, it interacts with a GABA-BZ receptor complex and shares some of the pharmacological properties of the benzodiazepines. 

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