Pharmacology is the study of the effects of drugs. The other interesting branch known as the “clinical pharmacology” is interested in the effects of drugs in humans by which therapy is individualised according to the needs of each patient (based on the nature of his disease and its severity). The epidemiology is study of distribution and determinants of diseases in populations.

Clinical pharmacology and epidemiology working together with their inputs and out comes resulted in the development of pharmacoepidemiology.

What is pharmacoepidemiology?

Pharmacoepidemiology is the study of the use of and the effects of drugs in large numbers of people worldwide during the post-marketing phase.

All drugs have adverse effect, but do pharmacoepidemilogy capable to prevent them? Yet, it can only follow up, detect, and prevent their recurrence using many tools especially by health care professionals and the patient themselves. As an example, if a patient is suffering from severe liver and mild renal dysfunctions, his liver is not efficiently working and consequently he is at a higher risk, than other patients, of suffering from many adverse effects when using other prescribed drugs.

Risk and benefit balance

Pharmacoepidemiology provides information for the benefits versus risks from the use of drugs, this give an excellent assessment of the famous risk/ benefit balance profile.

Clinical pharmacology is the study of two important fields:

1. Pharmacokinetics, it is the relationship between the administered dose of a drug and the blood level achieved. The actions involved are drug absorption, distribution, metabolism and excretion.
2. Pharmacodynamics, is the study of the relationship between drug level and drug efficacy.

During the pre-marketing clinical trial phases studying the clinical pharmacology of the drug, allow us to understand the effect(s) which could be observed when the drug is administered to the patient using the drug according a prescribed dosage schedule.

Pharmacoepidemiology is primarily concerned itself with study of adverse drug effects this is not other than a part of pharmacovigilance activity played during the post marketing surveillance phase.

Collecting, evaluating and studying spontaneous reports in which adverse drug reactions are reported helps in assessing the morbidity or mortality rates.

Pharmacoepidemiology relation with pharmacovigilance.

In studying Adverse Drug Reaction (ADRs) we study the case reports on an individual basis i.e. whether the adverse reaction was actually caused by the use of the drug. Here we are dealing with a case of subjective clinical judgment. But in the Adverse Event (AE), we need to conduct many controlled clinical studies to evaluate and finally consider whether the adverse reaction is evolved, and/or repeated more often in certain population than in others.

The need of pharmacoepidemilogy

As an important arm for pharmacovigilance, recently many voices are raised to consider using clinical trials in the post-marketing surveillance phase and not only depending on non-clinical or experimental methods to study drug safety issues after marketing the drug.  

All regulatory authorities are now interested in discovering the rare and non-listed ADRs from newly launched. They encourage pharmaceutical companies to implement a pharmacovigilance reporting system to following up their launched products worldwide and report the pharmacoepidemiology impact.

Post-marketing studies

Post-marketing studies explore and effectively explain how other contributing factors such as other diseases and/or other drugs might modify the efficacy and safety of the drug in use also explain the differences in drug regimen, and patients’ compliance. Pre-marketing studies of drug effects are limited in size; they are looking after carefully selected patients under a certain known environment and experimental conditions which is completely different from patients using the drug by their own in their real living environment.

Conclusion

Although if no adverse drug effects reported post-marketing, it’s a positive and reassuring point for health care professionals about the safety of the drug they are prescribed to their patients. Also its an indicator that the study conducted is fulfilling its systems on an ethical basis with a sense of responsibility towards its customers.

Pharmacoepidemilogy together with a successfully implemented pharmacovigilance system can minimise, prevent, and improve the use of drugs by discovering, at the post-marketing phase, the adverse effects at the level of general public use. This will ensure the safety and better use of drugs towards the needed efficacy for treating illnesses.

Contributor: Elie Magdalani