This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
There are two varieties of indigestion in which hydrochloric acid is especially indicated -the so-called "atonic" form, and the "acid" form - but the mode of its use is somewhat different for each.
Atonic dyspepsia occurs either in connection with general weakness or impaired hygienic conditions - for instance, in over-worked factory girls, seamstresses, etc., - or in well-fed person who tax their stomach with too much nitrogenous food while leading a sedentary life. The secretion of gastric juice is but scanty, and the patient suffers from weight and heaviness after food, from general oppression, and other signs of unfinished digestion. One indication for the treatment of such a condition is to supply additional acid to the gastric secretion; but, as we have reason to believe that adding such acid before a meal will check the formation of the naturally acid though scanty gastric juice, it is better to allow this to do what it can, and to prescribe our medicinal acid shortly after food has been taken, with the object of assisting nature, and not interfering unduly.1
In cases of "acid" dyspepsia, the patient suffers rather from heartburn and regurgitation of sour fluid, connected either with hyper-secretion from the gastric glands, or abnormal fermentation of starchy, saccharine, or fatty food. It is true that the symptoms may often be relieved by soda, but in many cases, more permanent relief will be given by dilute hydrochloric acid administered about half an hour before a meal. This will lessen the amount of the natural secretion, and will check fermentation.
It is only recently that this important distinction as to the time of taking an acid with reference to food has been recognized; many writers, Nothnagel for instance, are satisfied with recommending its use always before meals, and certainly if it be given after food, in cases of pyrosis or water-brash, it will aggravate the mischief; these are the true cases in which its use is indicated before meals, when it exerts an astringent ac- tion. It is contra-indicated in acute inflammatory, and also in organic disease; and in any case its use should not be continued too long, or the digestive property of the gastric juice will be impaired.
Headache, especially felt in the temple and brow, and marked giddiness are often connected with the dyspepsia above described, and are relieved by hydrochloric acid.