specific for the relative dosages in a given FDC product, providing a simpler overview compared to when looking at the profiles of each single drug individually. Such combined profiles can also include effects caused by interaction between the individual drugs that may be omitted in individual drug profiles. Since FDCs are reviewed by regulating agencies (such as the Food and Drug Administration in the United States), the active ingredients used in the FDCs are unlikely to exhibit adverse drug interactions with each other. However, FDCs may interact with other drugs that a patient is taking, so the usual medical and pharmaceutical precautions against drug-drug interactions or DDIs remain warranted. FDC drug products may be developed by a pharmaceutical company as a way to in effect extend proprietary rights and marketability of a drug product. Since FDCs may be protected by patents, a company may obtain exclusive rights to sell a particular FDC or formulation thereof, even though the individual active ingredients and many therapeutic uses thereof may be off-patent. Disadvantages There may not be an FDC available with the appropriate drugs and/or in the most appropriate respective strength(s) for a given patient, which can lead to some patients getting too much of an ingredient and others getting too little, as the AAO notes that FDCs "limit clinicians' ability to customize dosing regimens." In such cases an alternative possibility (instead of an FDC) is to use custom-compounded polypills prepared by a compounding pharmacist according to a prescription. (Pharmaceutical compounding is the practice of preparing individualized drug products for individual patients, which can aid with polypharmacy.) If an adverse drug reaction occurs from using an FDC, it may be difficult to identify the active ingredient responsible for causing the reaction. This problem might be alleviated by starting the medications individually and monitoring for reactions, and then switching to an FDC when no problems have been observed (assuming of course that it's the active ingredient causing the problem). Formulation scientists experience challenges in the development stages of multi-drug formulations such as compatibility issues among active ingredients and excipients affecting solubility and dissolution If one drug is contraindicated for a patient, whole FDC cannot be prescribed. References External links Dosage forms fi:Yhdistelmälääkkeet