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Bioequivalence is the development of a generic drug version of an already existing brand name version. This is one of the main reasons why a bioequivalence study doesn’t go through the same number of trials as a new type of drug. In spite of the difference, factors that influence the bioequivalence studies are similar to the ones affecting the bioavailability of drugs. 

Pharmaceutical Factors Affecting Bioequivalence Studies


Particle Size

The smaller the particle size, the better is the rate of dispersal. This means that by increasing the surface area, the bioavailability of drugs can be increased. 

Salt Form

The rate at which a particle of salt dissolves is different in comparison to the parental compound. Hence this directly affects bioavailability. 

Crystal Form

Amorphous forms dissolve faster in comparison to crystallized forms of the drug. This again goes to show that a crystal form would offer less bioavailability. 

Water Of Hydration

Anhydrous forms are more likely to attract water molecules and dissolve in them rather than hydrated crystal forms. With anhydrous drug form, the chances of bioavailability increase. 

Nature of Adjuvants And Excipients

Binding agents or filling materials have a high effect on the bioavailability of drugs. For a bioequivalence study, it is vital to be careful around drugs that have a low safety margin. 

Degree Of Ionisation

A better bioavailability is observed through the use of non-ionized, lipid-soluble drugs. This can be said in comparison to strongly basic or strongly acidic versions of drugs. 


Pharmacological Factors Affecting Bioequivalence Studies

Gastric Emptying And Gastrointestinal Motility

To expose drugs to the small intestine with more surface area, all factors resulting in gastric emptying help increase the bioavailability of drugs. 

Gastrointestinal Diseases

Many gastrointestinal diseases like Celiac or Crohn’s disease affects absorption. For example, if the bioequivalence drug is an alternative for a drug with amoxicillin, it should be noted that patients with Celiac disease are likely to experience less bioavailability of drugs. The dosage in such cases must be checked. 

Food And Other Substances

Commonly the gastrointestinal rate of absorption decreases after the ingestion of food. This can directly affect bioavailability and, therefore, bioequivalence. 

First-pass Metabolism

The bioavailability of the drug decreases upon passing the GIT. The drug, after that, passes through the portal system into the circulatory system. This is why the dosage of administration is higher than the actual amount of drugs available to act on target organs. 

Drug-drug Interactions

Antacids decrease the bioavailability of Tetracycline, and liquid paraffin decrease bioavailability of vitamins. These, besides many other interactions, are considered while making a drug. 

Pharmacogenetic Factors

Fast acetylators decrease, and slow acetylators increase the bioavailability of isoniazid. There are many such exceptions to be considered while analyzing bioavailability studies

These factors are crucial for conducting a bioequivalence study. While availing lab services from a CRO, it is essential to check if all such tests are conducted by the company to ensure drug safety and efficacy.