General anesthetics inhaled

Inhalation is the most common means by which ethers enter the body. The effects of various ethers may include narcosis, irritation of the nose, throat, and mucous membranes, and chronic or acute poisoning. In general, ethers are central nervous system depressants, eg, ethyl ether and vinyl ether are used as general anesthetics. 

Malignant hyperthermia (MH) is an autosomal-dominant pharmacogenetic disorder that is triggered by exposure to inhalation of general anesthetics, such as halothane. In susceptible individuals, these drugs can induce tachycardia, a greatly increased body metabolism, muscle contracture and an elevated body temperature (above 40°C) with a rapid rate of increase. Many cases of MH are linked to a gene for type 1 ryanodine receptor (RyRl). 

Despite the paucity of systematic studies in humans, the available evidence suggests that, like drugs such as alcohol, sedatives, and stimulants, inhalant drugs (i.e., solvents, general anesthetics, and nitrites) exert reinforcing effects and increase motor activity. Furthermore, with continuous use, these drugs appear to induce both tolerance and symptoms of withdrawal. 

Inhalation of other general anesthetics susceptible to abuse, such as ether and chloroform, appears to be limited to health professionals who have easy access to these compounds and who tend to use these dtugs in isolation. Recreational and social use of these substances has been somewhat limited by their high flammability and by frequent and intense undesirable adverse effects at moderate doses. It has been suggested that the abuse of ether or chloroform alone is a rare phenomenon (Delteil et al. 1974 Deniker et al. 1972), occurring usually in the context of dependence on othet substances, particularly alcohol (Krenz et al. 2003). 

Inhalation (general anesthetics) Dermal Single administration Single application I, II, III, NDA I... 

Ethane is really quite a simple molecule just two types of atoms, carbon andhydrogen, and eight atoms in all. Yet simple derivatives of ethane find important use in human medicine as inhalation general anesthetics. 

The earliest inhaled general anesthetic that found significant use is chloroform, CHCI3, more systematically trichloromethane, a simple derivative of methane. Chloroform was gradually replaced by diethyl ether, commonly known simply as ether, a safer and more effective molecule than chloroform. 

Diethyl ether was the inhalation anesthetic of choice during my childhood. Happily, 1 had rather little need of it. Ether was replaced years ago by a family of superior inhaled general anesthetics, most of which are ethane derivatives. The notable exception is another very simple molecule, nitrous oxide, N2O, frequently known as laughing gas. N2O has been around for a long time and was once a party drug. ... 

According to their mode of application, general anesthetics in the restricted sense are divided into inhalational (gaseous, volatile) and injectable agents. 

Anesthetic induction (give slowly [over 3 min]).-Reduce concentration of inhalation agents by 30%-50% for initial hour) 130-245 mcg/kg 0.5-1.5 mcg/kg/min or general anesthetic dependent on duration of procedure... 

N.P. Franks, W.R. Lieb, Stereospecific effects of inhalational general anesthetic optical isomers on nerve ion channels. Science 254 (1991) 427-429. 

General anesthetics are typically administered by intravenous injection or by inhalation. For many years, inhalation anesthesia was used for all types of surgical procedures. Recently, intravenous anesthesia has become a more widely used technique around the world. 

In the past decade, considerable evidence has accumulated that a primary molecular target of general anesthetics is the GABA receptor-chloride channel, a major mediator of inhibitory synaptic transmission. Inhaled anesthetics,... 

Inhaled (volatile) anesthetics potentiate the neuromuscular blockade produced by nondepolarizing muscle relaxants in a dose-dependent fashion. Of the general anesthetics that have been studied, inhaled anesthetics augment the effects of muscle relaxants in the following order isoflurane (most) sevoflurane, desflurane, enflurane, and halothane and nitrous oxide (least) (Figure 27-9). The most important factors involved in this interaction are the following (1) nervous system depression at sites proximal to the neuromuscular junction (ie, central nervous system) (2) increased muscle blood flow (ie, due to peripheral vasodilation produced by volatile anesthetics), which allows a larger fraction of the injected muscle relaxant to reach the neuromuscular junction and (3) decreased sensitivity of the postjunctional membrane to depolarization. 

Inhalation Rapid onset direct application for respiratory disorders large surface area for systemic absorption Chance of tissue irritation patient compliance sometimes a problem General anesthetics antiasthmatic agents... 

Hence, it is believed that general anesthetics exert most, if not all, of their effects by binding to one or more neuronal receptors in the CNS. This idea is a departure from the general perturbation theory described earlier that is, that the inhaled anesthetics affected the lipid bilayer rather than a specific protein. Continued research will continue to clarify the mechanism of these drugs, and future studies may lead to more agents that produce selective anesthetic effects by acting at specific receptor sites in the brain and spinal cord. 

General anesthetics are usually given by inhalation or by intravenous injection. 

Four types of inhalants are abused (1) anesthetic gases (2) industrial solvents, including a variety of hydrocarbons, such as toluene (3) aerosol propellants, such as various fluorocarbons and (4) organic nitrites, such as amyl or butyl nitrite. The mode of action of the inhalant anesthetics has been discussed in Chapter 25 General Anesthetics. 

The lungs are important for the excretion of volatile drugs. As a result of reduced respiratory capacity (Figure 61-1) and the increased incidence of active pulmonary disease in the elderly, the use of inhalation anesthesia is less common and parenteral agents more common in this age group. (See Chapter 25 General Anesthetics.)... 

General anesthetics are administered by intravenous, inhalation, or intramuscular routes. Adverse effects of general anesthetics are hypersensitivity, involuntary muscle movements, bronchospasm, cardiac arrhythmias, and respiratory... 

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