Anaesthetics

maybe this will help - there is a section dealing with it and its effects http://www.whatislife.com/reader/anaesthetics/anaesthetics.html

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... amino acids. Even though many alkaloids are poisonous (such as strychnine or coniine), some are used in medicine as analgesics (pain relievers) or anaesthetics, particularly morphine and codeine. Most alkaloids have a very bitter taste. Although formally an alkaloid, the class of pyrazoles contain ...

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... but they can pass literally through the lipidic bilayer or by canal proteins. Examples: Transport of lipidic molecules (as steroidic hormones), anaesthetics as ether, liposoluble chemicals, apolar substances (as atmospheric oxygen and nitrogen) and some polar molecules (as carbon dioxide, ethanol, ...

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