Introduction

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 be, for all intents and purposes, the same.

Birkett (2003) defined bioequivalence by stating that, "two pharmaceutical products are bioequivalent if they are pharmaceutically equivalent and their bioavailabilities (rate and extent of availability) after administration in the same molar dose are similar to such a degree that their effects, with respect to both efficacy and safety, can be expected to be essentially the same. Pharmaceutical equivalence implies the same amount of the same active substance(s), in the same dosage form, for the same route of administration and meeting the same or comparable standards.

Generic importance

Bioequivalence establishes generic drugs as interchangeable to the branded ones with similar therapeutic and side effect profiles. Bioavailability of drugs signifies the rate and extent to which their active ingredient is absorbed systemically after dosing. NorthEast BioLab performs regulated analysis for your bioequivalence and bioavailability studies to accelerate your regulatory submission and drug approval applications such as IND, BLA, ANDA, and NDA.

Most of the medicines or pharmaceuticals consumed orally reach the systemic circulation through the gastrointestinal tract. These drug compounds then enter the site of action through the systemic circulation. Bioavailability of drugs is measured by assessing the active ingredient (API) concentration of the drug and any metabolites in plasma or serum. The API concentration also helps in determining the active ingredient release from the drug compounds along with its absorption, distribution, metabolism, and excretion.

The three primary variables of pharmacokinetic studies used in assessing the bioavailability of drugs are i) maximum concentration of the drug in the systemic circulation (Cmax), ii) time to reach this concentration (Tmax), and iii) time-drug concentration area under the curve (AUC).

Path of bioequivalence

Bioequivalence doesn't require the full clinical trial process that the name-brand version had to go through. Instead, generic drugs only have to be bioequivalent, which means the company applying for approval must perform the following steps: Test the generic drug against the brand-name drug on two small groups of test subjects. Draw timed blood samples from each patient. Demonstrate through statistical analysis that any difference in the drug’s bioavailability in participants taking the brand name version versus participants taking the generic version is not clinically significant.

It is easier to make a bioequivalent form of a traditional pill or injectable drug than to make a bioequivalent form of a biologic drug. As a result, the generic versions of biologic drugs, called “biosimilars,” may have to undergo clinical trials to gain approval.

Absolute bioavailability compares the bioavailability of the active drug in systemic circulation following non-intravenous administration (i.e., after oral, buccal, ocular, nasal, rectal, transdermal, subcutaneous, or sublingual administration), with the bioavailability of the same drug following intravenous administration.

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Regards

Mary Wilson

Editorial office

Clinical Pharmacology and Toxicology Research

E-mail: pharmatoxicol@eclinicalsci.com