Antipyretics

Lessen production of heat..........................

Acting on tissue change....................

Quinine.

Cinchonine.

Quinidine.

Cinchonidine.

Berberin.

Benzoic acid.

Carbolic acid.

Picric acid.

Salicylic acid.

Salicylate of sodium.

„ quinine.

„ methyl.

(oil of winter-green).

Salicin.

Kairin.

Camphor.

Eucalyptol.

Thymol.

Other essential oils.

Alcohol.

Acting on the circulation.......................

Generally

Antimony salts.

Aconite.

Digitalis.

Veratrine.

Colchicum.

Thallin.

Locally

Wet cupping.

Leeches.

Dry cupping.

Blisters.

Poultices.

Increase loss of heat...

By dilating the cutaneous vessels, and increasing radiation..........

Alcohol.

Nitrous ether.

Antipyrin,1 thallin.

By increasing the loss of heat due to evaporation of perspiration

Sudorifics

Antimonial preparations.

Opium and ipecacuanha.

Nitrous ether.

By abstracting heat from the body

Cold bath.

Cold affusion.

Cold sponging.

Wet pack.

Ice to the surface.

Ice-bags to the neck.

Cold drinks.

Cold enemata.

Mode of action uncertain........................

Purgatives. Venesection.

The mode of action of those which affect the blood and tissues themselves has already been considered tolerably fully under the head of 'Oxidation of Protoplasm' (p. 67). They appear simply to diminish the temperature by lessening oxidation. The mode of action of antipyretics which produce their effect through the circulation, has not been investigated in detail with satisfactory exactitude, but it is supposed that by lessening the rapidity of the circulation through those parts of the body in which the increased tissue-change is taking place, the temperature is reduced.

Blisters will have this effect locally by causing contraction of the vessels in the inflamed part, as already described under the head of Counter-irritants (p. 343). Antipyretics, which increase the loss of heat, may do so (1) by causing greater dilatation of the vessels of the skin, and thus allowing a quicker radiation of heat from the body; (2) by augmenting the secretion of sweat: and thus carrying off heat by means of evaporation (see Diaphoretics, p. 440); or (3) they may actually remove warmth from the body, as cold baths, cold affusion, cold sponging, wet packing, cold enemata, or ice to the surface.

1 Bettelheim, 'Ueber das Antipyrin,' Wien. rued. Jahrbiicher, 1885.

Uses. - Antipyretics are used to lower the temperature when it has risen above the normal, whatever be the cause. A high temperature may be produced simply by prolonged exposure to heat. This exposure and the rise in temperature it occasions, seems to induce increased tissue-change, and this increase of the tissue-change will keep up a febrile temperature, even after the external temperature has fallen. Such thermal fever is found in warm climates, and in it quinine injected subcutaneously seems to be very efficient.

A high temperature may also occur from specific fevers, as typhus, typhoid, scarlet fever, measles, and acute rheumatism. The most rapid and powerful antipyretic in such cases is the application of cold by bathing, or sponging; and probably next in efficiency come large doses of quinine or salicylate of sodium. [n typhoid fever, salicylate of sodium does not seem to act so rapidly as it does in acute rheumatism.

Venesection, though formerly the antipyretic which was chiefly relied upon, has now fallen to a great extent out of use-probably from its having been very much abused.

In persons suffering from acute inflammation of the lungs or bronchi, where the amount of lung-tissue which remains sound is insufficient to aerate the whole mass of blood, and the patient is becoming livid, small bleedings are serviceable; they not only relieve the breathing, but lessen delirium which may be present.

Venesection lowers the temperature for a short time, but it soon rises again in many cases, so that bleeding alone is by no means a powerful antipyretic,1 unless the quantity of blood abstracted be so great as probably to injure the patient seriously; yet in combination with other antipyretics it may sometimes be of very great service.

Local bleeding by leeches or by wet cupping sometimes gives very great relief, lessening both local inflammation and the general symptomatic fever consequent upon it, in pneumonia, pleurisy, pericarditis, peritonitis, etc. In such cases blisters may be used to diminish the local inflammation, and thus aid the action of other antipyretics.

Vascular antipyretics, such as aconite and digitalis, also seem to be of more service in symptomatic fever than they are in specific fevers.

1 Wunderlich's Medical Thermometry, pp. 118, 134, 378, New Sydenham Society's edition.

Purgatives take an intermediate place between antipyretics which lessen the production of beat by acting on the tissues, and those which act on the circulation. They diminish the force of the circulation, and may in this way lessen the production of heat. But it is not impossible also, although this is a point on which we have not sufficient information, that they may do so by removing from the body substances whose effect when present in the circulation or tissues would be to maintain the high temperature.

Amongst antipyretics which increase the loss of heat we have: first, alcohol, which is included also in the former list of those which lessen the production of heat, for it appears to act in both ways, both diminishing oxidation and also increasing the loss of heat. It does this by dilating the vessels of the skin and allowing free radiation from the surface, and also by the cooling effect of evaporation of the sweat, although its action as a sudorific is not very marked. Antipyrin seems to act in a similar manner.

We have also the whole class of sudorifics (p. 440). One of the most useful of these in checking a febrile condition just at its outset is a dose of compound ipecacuanha powder, or Dover's powder, which has now, to a great extent, taken the place of the older remedy having a somewhat similar action, viz. antimonial powder, or James's powder.

Another mixture in great favour is acetate of ammonium and spirit of nitrous ether. The most powerful, however, of all remedies which increase the loss of heat is the application of cold water or ice. The mode of applying these is discussed at page 464.