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Bioequivalence is a term in pharmacokinetics used to assess the expected in vivo biological equivalence of two proprietary preparations of a drug. If two products are said to be bioequivalent, it means that they would be expected to have the same bioavailability, duration of action and efficacy.
In determining bioequivalence, pharmacokinetic studies are conducted on each of the preparations in volunteer subjects. Serum plasma samples are obtained at regular intervals and assayed for drug concentration. This data can then be used to assess key pharmacokinetic parameters such as area under the curve (AUC), peak concentration (Cmax), time to peak concentration (Tmax), and absorption lag time (tlag). Testing should be conducted at several different doses, especially when the drug displays non-linear pharmacokinetics.
In Australia, the Therapeutics Goods Administration (TGA) considers preparations to be bioequivalent if the 90% confidence intervals (90% CI) of the transformed natural log ratios, between the two preparations, of Cmax and AUC lie in the range 0.80-1.25. Tmax is only considered important if the onset time is therapeutically relevant (e.g. for analgesics).
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