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.
A simple pneumonia usually terminates favorably, independently of medicine, and requires at least no active interference; but, under certain conditions and complications, phosphorus has proved, in my experience, a valuable adjuvant. Thus, if at the commencement of an attack adynamia is very pronounced, this medicine is indicated. It is curious that the most amenable to its action seem to be adult subjects previously robust, and old persons. It is a matter of common observation that the nerve-power fails more rapidly in severe illness attacking such subjects, than it does in the young or the simply delicate. Some degree of biliary disturbance usually accompanies the early stages of pneumonia, and so long as this does not assume a very aggravated form, 1 have found it a good indication for phosphorus treatment, and especially if prostration be extreme. Again, it is good in ordinary cases with difficult muco-sanguineous expectoration and very marked lowering of strength and evening exacerbations; also in later stages, when either pyrexia has subsided and the patient is left very feeble, and does not progress toward convalescence; or again, when red hepatization is complete, fever and prostration increase, and suppuration is imminent- although, when pus has actually formed, phosphorus is contra-indicated.
Dr. A. Thompson, speaking highly of the value of phosphorus in pneumonia, remarks that success depends much on the dose given, and in his opinion the better results of older practitioners were traceable to their use of full doses, toxic effects being less known and consequently less feared by them. He says that "no caution need limit the quantity of such a preparation as the tincture, the only limit to be recognized being improvement in the patient." He commonly orders 1/12-gr. dose in the cases referred to, but I cannot agree either with this theory or practice; my best results have been obtained with 1/200 to 1/100 or 1/50 gr. given every two to four hours.
I have also had good results from phosphorus in chronic pneumonia; but when it occurs in tuberculous subjects with tendency to hemorrhage, this drug should be avoided. In acute or chronic cases, complicated with bronchitis, phosphorus is less appropriate than other remedies.