The cheapest and most generally obtainable salt is the sulphate. It is soluble in 720 parts of water and contains 74% of alkaloid. The opinion now prevails that this is one of the less desirable of forms for the administration of quinine. It is frequently obtained in pill or tablet form and it must not be forgotten that such preparations may be almost stone-like and pass through the alimentary tract without absorption. If used it is best to give it in acid solution made by dissolving 5 grains of quinine sulphate in one teaspoonful (1 dram) of water with one drop of concentrated hydrochloric acid.
Dosage of Quinine.—The ordinary full dose of quinine for an adult is 10 grains repeated three times in a day or 30 grains daily. Some authorities recommend 15 grains three times daily (45 grains) at the commencement of treatment and such dosage seems to be just as efficient as the larger dose of 60 grains in a day. In cinchonism we have ringing in the ears, fullness in the head, deafness and dizziness. For children Bass recommends 1/20 of the adult dose for each year of age so that a child of 5 years age would receive ¼ of the adult dose. Beyond 15 years of age the dose is that of an adult.
There now seems to be a tendency to use the alkaloid itself instead of its salts, it having been found that the alkaloid and its very insoluble tannate are absorbed from the digestive tract equally as well as the soluble salts. Quinine is almost insoluble in water (1-1560) and hence has less bitter taste than the soluble salts. It is also less haemolytic so that it may be used with greater safety where blackwater fever is feared.
Euquinine or ethylcarbonate of quinine contains 81% quinine, and is only soluble in 1-12,000 parts of water, hence its comparative tastelessness. It is expensive.
Quinine tannate contains only about 30% of quinine and is practically insoluble in water. It is often given to children in chocolate tablet form. It can often be taken by those who suffer disagreeable effects from other salts. The dose should be 2½ times that of quinine sulphate.
Until recently the bimuriate (72% of alkaloid and soluble in 1 part of water) or the chlorhydrosulphate (74% of alkaloid and soluble in 2 parts of water) have been considered the most desirable salts for hypodermic injections or oral administration. At present, owing to its extensive use in local anaesthesia and incident availability, bimuriate of quinine and urea is to be recommended for intramuscular use. It contains 60% of quinine and is soluble in an equal amount of water.
It has been found to have a slightly greater tendency to produce amblyopia than other quinine salts and should not be used intravenously.
In a very important series of experiments on prisoners, MacGilchrist found that hydroquinine (a synthetic product of quinine) was about 20% more efficient than quinine. Cinchonine was about the same as quinine while quinidine was about one-half as potent as quinine.
Acton has praised the value of cinchona febrifuge (the combined alkaloids of cinchona) given in daily doses of 21 grains for ten days.