[1] Terms like "combination drug" or "combination drug product" can be common shorthand for an FDC product (since most combination drug products are currently FDCs), although the latter is more precise if in fact referring to a mass-produced product having a predetermined combination of drugs and respective dosages (as opposed to customized polypharmacy via compounding[2]).
[3] When a combination drug product (whether fixed-dose or not) is a "pill" (i.e., a tablet or capsule), then it may also be a kind of "polypill" or combopill.
Initially, fixed-dose combination drug products were developed to target a single disease (such as with antiretroviral FDCs used against AIDS).
This is because each FDC product is mass-produced, and thus typically requires having a critical mass of potentially applicable patients in order to justify its manufacture, distribution, stocking, etc.
Over-the-counter medicines: Prescription drugs: In addition to simply being a means of facilitating the general advantages of combination therapy, specific advantages of fixed-dose combination (FDC) drug products include: