A fixed dose combination (FDC) is a formulation of two or more active ingredients combined in a single dosage form available in certain fixed doses. Fixed dose combination drug products may improve medication compliance by reducing the pill burden of patients.

Typically, fixed dose combination drug products are developed to target a single disease (such as with antiretroviral FDCs used against AIDS). However, FDCs may also target multiple diseases, such as Caduet. Caduet contains atorvastatin to treat hypercholesterolemia and amlodipine to treat hypertension.

Since FDCs are reviewed by the Food and Drug Administration, the active ingredients used in the FDC are unlikely to exhibit adverse drug interactions with each other. However, FDCs may interact with other drugs that a patient is taking.

While FDCs may reduce pill burden, there are some disadvantages. If a dosing adjustment is warranted, there may not be a FDC available in the most appropriate strength for the patient. Additionally, if an adverse drug reaction occurs from using a FDC, it may be difficult to identify the active ingredient responsible for causing the reaction. However, this problem may be avoided by starting the medications individually and monitoring for reactions, and then switching to a FDC when no problems have been observed.

Profit motive

Fixed dose combination drug products may be developed by a pharmaceutical company as a way to extend the marketability of a drug product. Since FDCs may be protected by patents, a company may obtain exclusive rights to sell the FDC, even though the individual active ingredients may be off-patent.