Hi,

Type F adverse drug reactions (F=Failure; lack of response) occur as a result of an unexpected failure of therapy.

The intention of the treatment is to obtain a positive response in the patient. The doctor uses the drug for a specific purpose and the goal is to obtain the highest possible benefit from the treatment for the patient. However, if there is no positive response to treatment, it may be an exacerbation of the disease. The process can change its clinical picture. The doctor cannot control the course of the disease. This not only means that there is no benefit to the patient. It also means an increased risk that the disease will move to another stage that will be even more difficult to treat/control. And, depending on the disease, it can be very dangerous/risky way. This is why lack of benefit (no effect) could be defined as adverse (unfavorable, disadvantageous, unprofitable). Lack of efficacy is one of the key elements of benefit-risk analysis (see reference below).

https://www.ema.europa.eu/en/documents/report/benefit-risk-methodology-project_en.pdf

"...lack of expected efficacy (LEE) events should always be reported in the same way as for other adverse events"

https://www.ema.europa.eu/en/documents/other/questions-answers-adverse-event-reporting_en.pdf

"....lack of therapeutic efficacy should be reported within a 15-day time frame. If no seriousness criterion is available, it is acceptable to submit the ICSR within 15 days as non-serious"

https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-good-pharmacovigilance-practices-module-vi-management-reporting-adverse-reactions_en-0.pdf

Best regards

Tomasz

Type F reactions refers to unexpected failure of therapy, where a drug undesirably increases or decreases in efficacy. For example, the decreased clearance of a drug by dialysis, or the decreased effect of antibiotics due to resistance. An adverse drug event occurs during drug therapy but does not necessarily have any causal relationship with the drug, whereas an adverse drug reaction is directly related to the drug and occurs in the course of its appropriate use.

Telechea, H., Speranza, N., Lucas, L., Giachetto, G., Nanni, L., & Menchaca, A. (2012). Reacciones adversas a medicamentos en una unidad de cuidados intensivos pediátrica. Farmacia Hospitalaria, 36(5), 403–409.

Type F reaction can happen when the medicine contains less than the expected quantity of active ingredient. This happens in Falsified, Spurious or Sub standard or Fake medicines

While it's true that these reactions are different from other types of adverse reactions (e.g., Type A, which are dose-dependent and predictable, or Type B, which are idiosyncratic and less predictable), they are still considered adverse because they represent a negative outcome for the patient.

There are several reasons why a therapy might fail, including:

Although Type F reactions do not necessarily involve direct harm caused by the drug itself, they are still classified as adverse because they represent a failure to achieve the desired therapeutic outcome, which can lead to negative consequences for the patient's health