Fixed-Dose Combinations (FDC)

Fixed-Dose Combinations (FDC)

1. Definition & overview

• A fixed-dose combination (FDC) is a pharmaceutical preparation containing two or more drugs combined in a single dosage form in a fixed (predetermined, non-adjustable) ratio of doses (KDT 8e Ch.5, p.72).
• A large number of pharmaceutical preparations contain two or more drugs in a fixed-dose ratio — FDCs are among the most common product types in the Indian market, where polypharmacy combination products proliferate (KDT 8e Ch.5, p.72).
• The single combined dosage form is delivered as one tablet, capsule, or formulation, so the patient receives all components together each time the unit is taken (KDT 8e Ch.5, pp.72–3).
• Conceptually distinct from free (extemporaneous/loose) combination, where the same drugs are co-prescribed as separate units that the prescriber can independently titrate — the defining feature of an FDC is the loss of independent dose adjustment once the ratio is fixed (KDT 8e Ch.5, p.72).
• The clinical pharmacology of FDCs sits at the intersection of pharmacodynamics (does the combination make therapeutic sense?), pharmacokinetics (do the components behave compatibly?), prescribing rationality, and drug regulation — and so the topic is examined under "rational prescribing / rational drug use" rather than under a single drug class (Padmaja 7e Ch.5, pp.74–5).
• ⚠ Regulatory definition (India): an FDC is legally treated as a "new drug" the first time two approved drugs are combined, and therefore requires central (DCGI) safety-and-efficacy approval before manufacture — the full statutory route is set out in the Indian regulatory framework section below (KDT 8e Ch.5, p.72; CDSCO). [CDSCO]