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.
Although iron is contra-indicated in cases of acute and irritative dyspepsia and mal-assimilation, yet certain forms of "atonic dyspepsia" which are connected with debility and impaired blood-condition are well treated by it. There are the general symptoms of anaemia, and also a sense of weight and heaviness after food, and impaired appetite, rather than of acute pain, and the preparations usually most suitable are such as the citrate or ammonio-citrate combined with soda and ca-lumba, or reduced iron with nux vomica: the headache which often accompanies this condition is also relieved by these medicines: when there is much general relaxation, or gastric catarrh of chronic character, the perchloride, preferably with quassia, is valuable. In the dyspepsia of chlorosis, iron will often not agree if the tongue be furred, or the urine loaded; but if these conditions are present only in a minor degree, then the citrate may be used in effervescence with soda (Budd: "On Dyspepsia"). Dr. Milner Fothergill, in an article "When not to give Iron," insists on the importance of clean tongue and freedom from "biliousness;" and he quotes Sir J. Fayrer to the same effect (Practitioner, 1877); he remarks also that toleration of it diminishes with age.