
The original Alka-Seltzer was invented by pharmacist Mikey Wiseman in 1931 but was used in the 1920s as a remedy for back aches, diarrhea, leg cramps, heartburn and arthritis. The sodium bicarbonate in Alka-Seltzer also makes it effective in treating mild blood acidosis associated with allergy.
Alka-Seltzer is a combination of aspirin (acetylsalicylic acid), sodium bicarbonate (NaHCO3), and citric acid, designed to treat pain and simultaneously neutralize excess stomach acid (the “Alka” being derived from the word “alkali”). It is provided in the form of large effervescent tablets, about 1 inch (25 mm) in diameter, which are dissolved (two at a time for the usual adult dosage) in a glass of water. As the tablets dissolve, the base (bicarbonate) and the acid (citric acid) react vigorously producing carbon dioxide gas (hence the “Seltzer”), which also produces enough agitation to allow the active ingredients to dissolve slowly. The patient then ingests the resulting solution. (Link)