Pharmacokinetic studies for proving bioequivalence of orally inhaled drug products—critical issues and concepts

The inhalational drug market, especially the generic market, has a tremendous growth potential globally (GBI Research, 2011; Espicom, 2013; Transperancy: Market Research, 2013). Generics are drugs that are bioequivalent to the approved drugs. The United States Food and Drug Administration (FDA) has defined bioequivalence as (U.S. FDA, 2014), “The absence of a significant difference in the rate and extent to which the active ingredient or active moiety in pharmaceutical equivalents or pharmaceutical alternatives becomes available at the site of drug action when administered at the same molar dose under similar conditions in an appropriately designed study.” The inhalational route of drug delivery has various advantages (Morgan et al., 1986; Rau, 2005):