Sympathomimetics

The actions are summarised in Table 22.1. The classic, mainly endogenous substances will be described first despite their limited role in therapeutics, and then the more selective analogues that have largely replaced them.

CATECHOLAMINES5

For pharmacokinetics, see above.

Adrenaline (epinephrine)

Adrenaline (a- and P-adrenoceptor effects) is used:

• as a vasoconstrictor with local anaesthetics (1:80 000 or weaker) to prolong their effects (about 2-fold)

• as a topical mydriatic (sparing accommodation; it also lowers intraocular pressure)

• for severe allergic reactions, i.m., i.v. (or s.c.). The route must be chosen with care. For adults, adrenaline 500 micrograms (i.e. 0.5 ml of the 1 in 1000 solution) may be given i.m. and repeated

5 Traditionally catecholamines have had a dual nomenclature (as a consequence of a company patenting the name Adrenalin), broadly European and N. American. The latter has been chosen by the World Health Organization as International Nonproprietary Names (INN) (see Ch. 6), and the European Union has directed member states to use INN. Because uniformity has not yet been achieved and because of the scientific literature, we use both. For pharmacokinetics, see above.

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