Anaesthetics, general Alcohol

Volatile lipophilic substances like volatile general anaesthetics, ethyl alcohol, paraldehyde are excreted by the lungs. These volatile substances and certain gases that enter the body through the respiratory tract in the form of aerosol are excreted by this route. 

CNS depressants + CNS depressants Alcohol + Antihistamines Ben KJiazepines + Anaesthetics, general Opioids + Benzodia pines Impaired psychomotor skills, reduced alertness, drowsiness, stupor, respiratory depression, coma, death... 

In a double-blind study in 11 healthy subjects there were several instances when alcohol 0.25 to 5 g/kg (equivalent to 1 to 3 drinks) enhanced the effects of nitrous oxide 30% in oxygen, inhaled for 35 minutes. Some effects were seen with the drug combination, which were not seen with either drug alone these included subjective effects and delayed free recall. For mention of the effect of alcohol following anaesthesia, see Anaesthetics, general -I- Alcohol , p.92. 

Meyer, in 1901, was the first to suggest that alcohol acted like general anaesthetics by dissolving into cell membranes and thereby disrupting the lipid network that comprises the cell wall. It is now known that, at pharmacologically relevant concentrations (in the range 25-100 mmol/L),... 

When it comes to physicochemical (biological) properties the common structural formulae obscure rather than explain the problem. One of the most convincing examples may be the anaesthetic activity of chemicals. Among general anaesthetics one can identify such diverse chemical families like hydrocarbons, alcohols, ethers, barbiturates, nitrous oxide, steroids, etc. Each one must have anaesthetic activity encoded in its structure but how is it discovered using conventional chemical symbolic The planar or three-dimensional chemical notation can be an obstacle to making a breakthrough in chemistry. 

Alcohol acts on the central nervous system in a manner broadly similar to volatile anaesthetics, exerting on cells a generally depressant effect that is probably mediated through particular membrane ion channels and receptors. Alcohol enhances (inhibitory) GABA-stimulated flux of chloride through receptorgated membrane ion channels, a receptor subtype... 

Alcohol has effects that resemble those of general anaesthetics. It inhibits prcsynaptic entry (and hence transmitter release) and polentiute.s OABA-medtated inhibition. Considerable tolerance occurs to alcoltol. but the mechanism. involved are poorly understood. Prcsynaplic Ca channels may increa.se in number, so that when alcohol is w ithdrawn transmitter release is abnormally high and this may contribute to the withdrawal syndrome. 

Depressants may be hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, weak acids (like the barbiturates), weak bases, or sulphones. They are the selectively toxic agents used in medicine as hypnotics and general anaesthetics. This is the only kind of biological activity in which structure simply does not matter (there is much more about this in Chapter 15). See Section 3.3 for the general function of partition effects in securing selective distribution of drugs. 

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