Taking part in a bioequivalence study

What is compared and why

A bioequivalence study shows that two medicines with the same active substance behave comparably in the body: the differences in the rate and extent to which the substance becomes available to the body (for tablets and capsules, by its concentration in the blood) stay within limits set in advance (EAEU Rules, clauses 2, 3 and 11). For example, a generic is compared with the original: such studies are needed, among other things, to register a generic (clauses 1 and 8; Article 38, Part 2 of Law No. 61-FZ). The medicine it is compared with is called the reference medicine.

This is not treatment and not a check of your health: the study evaluates a medicine. That is why you must be warned in advance if no medical benefit to you is expected (EAEU GCP Rules, clause 4.8.10, item “з”).

Who takes part

As a rule, the studies are conducted among healthy volunteers (clause 27); if a medicine poses an obvious threat to the health of a healthy person, patients may be enrolled instead (clauses 27 and 31). The age is at least 18, and the body mass index is, where possible, 18.5–30 kg/m² (clause 28). Conformity is confirmed by laboratory tests, a medical history and a physician’s examination (clause 29), and the study doctor decides under the protocol of the specific study. See “Who can take part”; you can also take the quick self-check on the enrolment page.

How taking part works

The standard design under the EAEU Rules is a randomised two-period crossover study in two sequences with a single dose (clause 15); other designs are possible and are described in the protocol (clause 16). In plain terms, it looks like this:

Screening. A talk with the doctor, informed consent and an examination: they check whether you meet the protocol criteria. The doctor decides.
First period. You receive one of the two medicines; which one is decided by chance (randomisation). Doctors and nurses monitor how you feel, and blood samples are taken at set times.
Washout. The substance leaves the body. By the start of the second period its concentration must be below the detection limit: usually five half-lives are enough for this (clause 15). How many days that is depends on the medicine and is stated in the protocol.
Second period. You receive the other medicine; monitoring and sampling go the same way.
Final check-up. After the periods, the doctor carries out an examination and tests if the protocol requires them (clause 29).

As a rule, on the days of taking the medicine and of blood sampling, volunteers stay in the clinic under observation; the protocol sets the routine, the visit schedule and the duration, the doctor tells you before you sign the informed consent, and they are stated in the document itself. Because each participant is compared with himself or herself, this design is called crossover.

What you need to follow

The protocol sets the rules a participant follows during the study: the diet, restrictions on medicines and alcohol, the time to arrive and to take the medicine. Follow them strictly, because both your safety and the reliability of the results depend on it. Report any change in how you feel at once.

Risks and inconveniences

Any medicine may cause adverse reactions, and taking part in a study is no exception. The study doctor tells you about the known risks before you sign the consent, and the contacts for what to do if you feel worse are stated in the informed consent. Inconveniences include restrictions on your routine, repeated blood sampling and staying in the clinic on the days of dosing and sampling.

Your rights

Taking part is voluntary: you may withdraw at any stage, without penalty or loss of benefits (Article 43, Part 4 of Law No. 61-FZ; EAEU GCP Rules, clause 4.8.10, item “н”).
The study is conducted under a permit from the Ministry of Health, and its documents undergo ethics review; taking part is not allowed without a life and health insurance contract (Articles 38, 39.1, 44; more on the page “Insurance for participants”).
The terms of payments, if any, are stated in the informed consent. See “Payments and compensation”.

How to check that a study is genuine is described on the page “How to check that a study is genuine”. To sign up, leave your contact or call +7 (499) 346-21-15.

Sources

EAEU Bioequivalence Rules — Council Decision No. 85 (as amended): clauses 1, 2, 3, 8, 11, 15, 16, 27–29, 31.
EAEU Good Clinical Practice Rules — Council Decision No. 79 as restated by Decision No. 63 of 1 August 2025 (in force from 10 March 2026): clauses 4.3.4, 4.8.10.
Federal Law No. 61-FZ of 12 April 2010 “On the Circulation of Medicines”: Articles 38 (Part 2), 39.1, 43 (Part 4), 44 — text on ConsultantPlus.

Questions and answers

Is this treatment?

No. As a rule, healthy people take part, and the purpose is to compare how the substance from two medicines becomes available to the body (for tablets and capsules, by its concentration in the blood). If no medical benefit to you is expected, you must be told so before you sign the consent (EAEU GCP Rules, clause 4.8.10, item “з”).

What is a reference medicine?

It is the medicine the study medicine is compared with: for example, the original medicine when it is compared with a generic. Which medicines take part in a specific study is stated in the protocol and explained at the talk with the doctor.

Why are there two periods?

In the first period you receive one medicine and in the second the other: each participant is compared with himself or herself, and the order is decided by chance (randomisation). This is the standard design under the EAEU Rules (clause 15).

Can I withdraw if I change my mind?

Yes, at any stage, without penalty or loss of benefits; you do not have to give reasons (Article 43, Part 4 of Law No. 61-FZ; EAEU GCP Rules, clause 4.8.10, item “н”, and clause 4.3.4). Tell the study doctor: he or she will explain how to end participation properly.

This material is general information and does not replace a physician’s advice. The decision to enrol a person in a study is made by the investigator physician.