DECHALLENGE AND RECHALLENGE IN PHARMACOVIGILANCE

Introduction

Dechallenge and rechallenge are the terms used in pharmacovigilance concerning
the action taken with a drug after an adverse event that may be caused by a drug
taken by a subject or a patient.

To understand Dechallenge and rechallenge, we will consider the scenario
portrayed in the following figure.

A person takes a drug or a medicinal product under the following conditions.

1. During clinical trials under the supervision of an Investigator.
2. Consults a doctor for treatment, may get hospitalized, and use any medicinal product.
3. Self-treatment by purchasing a medicinal product from a pharmacist.

In any of the mentioned situations, any occurrence of an adverse event after consuming the drug needs action. The first action is to Consult the Health Care Professional.

Then the Investigator or Physician takes one of the following actions

• Reduce the dose
• Temporarily or
• Permanently stop the drug

What is the Dechallenge?

When a drug is stopped permanently, or temporarily, or the dose is reduced significantly, in response to the occurrence of an adverse event.

Why is it done?

• It is done to relieve the subject or patient of the adverse event from which he/ she is suffering.
• Also, to assess the causal relationship between the drug and the adverse event.

How to interpret Dechallenge results?

Positive- when the symptoms decrease or disappear.
Negative- when the symptoms persist or worsen.
Unknown- when no information is available.

Not Applicable-

• When the event outcome is death and we do not know when the suspect drug was discontinued.
• When a single dose was given and never given again.
• And if treatment was given for the adverse event.

What is the use of Dechallenge?

It gives evidence to prove the causal relationship between the drug and the adverse event.

Where is it done?

It is done in clinical trials to prove the causality of the drug with an adverse event or in planned treatment where we test any allergic reaction to a drug in a patient. Till this point, we can suspect that the drug may have caused the adverse event. To confirm our statement, we need to take another action...restart the drug again and observe for the reappearance of the same adverse event again.

What is Rechallenge?

When the drug is restarted after dechallanging, it is called Rechallenge

Why is it done?

This proves the causal relationship between the drug and the adverse event.
When is it done?

After dechallange i.e. after the drug was stopped permanently or temporarily.

What is the purpose?

To confirm the adverse event is related to medicinal product use. So that further action can be taken to modify its use of it.

Why do we rechallenge even after knowing causality?

The Investigator or the Physician may sometimes need to restart the drug as few drugs cannot be stopped abruptly due to the risk of withdrawal symptoms so they take a step to restart it again by altering the dosage. This is called Rechallenge as the drug is reintroduced. Rechallenges should be done under the supervision of health professionals.

How to interpret Rechallenge?

Positive- When the same signs and symptoms reappear after restarting the drug.
Negative- When the signs and symptoms of the adverse event DO NOT
Reappear- after restarting the drug.
Not Applicable- in cases where treatment is given for the reaction/ event

Dr. Noor E Ayeen Khatoon (MBBS)
Student ID: 160/0922