Chronos,
in the above example, digoxin (small d) is substance’s “common” name. In general, millions of known chemicals/substances/compounds, do not have a “common” name. A chemical name can be usually made, such as monohydrochloride of [4S-4alpha,4aalpha,5aalpha,6beta,12aalpha,)]-4-(Dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,6,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-2-naphthaacenecarboxamide. A name like this still does not convey stereoisomeric qualities of the compound, so if one chemist would tell(!) this name to another one, the latter wouldn’t be able to recreate it, because more than one srereoisomere will fit the descriptive name. So, for used compounds, “common” names are invented (out of the blue or according to twisted and arbitrary rules). The above compound is called tetracycline HCl [i.e., hydrocloride]. Under this name it’s entered in the USP (US Pharmacopeia), medical and pharmacological textbooks, pharmacopeias of other countries, etc. All people see “tetracycline HCl” (with small t) and they know exactly what is meant. Lederle Laboratories (division of American Cyanamid Co, 1 Cyanamid Plaza, Wayne, NJ07470), sells a mixture of this compound in capsules as Achromycin V (Roman 5). Roberts Pharmaceutical Corporation makes a solution for local skin application with this compound, which does not differ chemically or biologically from tetracycline HCl and sells it as Topicycline. Apothecon (Bristol-Myers Squibb) sells it as Sumycin, Mylan Pharmaceuticals sells it as Tetracyclin HCl Capsules. The names are capitalised. It means that a product has a “parent”, and that it’s not a chemical or “common” name.
Back to digoxin. Lanoxin (cap.L)is the trade (brand) name under which the drug is marketed by Burroughs Wellcome. Another company (or BW) may market it under a different name, or, after the patent expires, as digoxin. So, there is no such substance as Lanoxin. There is digoxin, which is good for sick heart. Lanoxin is just a name. Any other name can be attached to digoxin. The manufacturers ARE REQUIRED to always use chemical or common name, as it appears in the USP (not PDR) whenever the trade/brand name is mentioned. So, the drugs can be compared.
It was long, but I hope that now you better understand that there is only one chemical compound with certain biological qualities called acetaminophen. By using “inactive” ingredients, drug companies can change some qualities, like color, taste, etc. Changing certain qualities significantly, such as solubility, may interfere with bioavailability, etc., and will require approval by the FDA. You probably know acetaminophen as Acoda#3 (Everett), Anexia5/500 (SmithCline Beecham), Excedrin (Bristol Myers),Tylenol (McNeil), and many other names. They all will assure you that acetaminophen is no good. It does not taste good, it’s of ugly color, it may kill you if you don’t pay them enough money, etc. Do not believe them.