A combination drug or a fixed-dose combination (FDC) is a medicine that includes two or more active ingredients combined in a single dosage form. 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). And it should also be distinguished from the term "combination product" in medical contexts, which without further specification can refer to products that combine different types of medical products—such as device/drug combinations as opposed to drug/drug combinations. Note that 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). However, FDCs may also target multiple diseases/conditions. In cases of FDCs targeting multiple conditions, such conditions might often be related—in order to increase the number of prospective patients who might be likely to use a given FDC product. 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. Common combination drugs Over-the-counter medicines: Dimenhydrinate (8-chlorotheophylline/diphenhydramine) — used to treat motion sickness and nausea Glucose/fructose/phosphoric acid — antiemetic taken to relieve nausea and vomiting Prescription drugs: Adderall (dextroamphetamine sulfate/amphetamine sulfate/dextroamphetamine saccharate/amphetamine aspartate monohydrate) — treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. Aspirin/paracetamol/caffeine — pain treatment, especially tension headache and migraine Caffeine/ergotamine — treatment of headaches, such as migraine headache. Nirmatrelvir/ritonavir (Paxlovid) — granted emergency use authorization (EUA) by the US Food and Drug Administration (FDA) for the treatment and management of COVID-19. Advantages 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: Improved medication compliance by reducing the pill burden of patients. Note that pill burden is not only the number of pills needing to be taken, but also the associated burdens such as keeping track of several medications, understanding their various instructions, etc. Ability to compose combined profiles of for example pharmacokinetics, effects and adverse effects that may be