Pharmacoepidemiology Overview and Studies

Pharmacoepidemiology Overview

• Pharmacoepidemiology is a science focused on studying the effect of medications on populations' health.
• Epidemiology initially focused on infectious outbreaks, then expanded to encompass the health of populations.
• It studies drug use in real-world settings, evaluating effectiveness and safety.

What Pharmacoepidemiology Studies

• Fundamental Pharmacology: Examines the mechanism of action of a drug.
• Observational Clinical Pharmacology: Studies the impact of a drug on clinical parameters.
• Comparative Clinical Pharmacology: Investigates the difference in drug effects through clinical trials.
• Pharmacoepidemiology: Assesses whether clinical trials accurately reflect medication's real-world impact.

Proof of Efficacy and the CAST Study

• Fundamental pharmacology and logical reasoning can suggest a drug is useful.
• Class 1 antiarrhythmics were thought to be helpful after myocardial infarction based on physiological insight.
• However, after clinical trials (such as the CAST study), it was apparent the drugs didn't prevent harm or improve health outcomes.
• The CAST study (1991), a randomized clinical trial, evaluated flecainide and encainide, showing increased risk of death.

Differences Between Clinical Trials and Pharmacoepidemiology

• Clinical trials have controlled environments, targeted populations, regulated drug intake, and controlled treatment monitoring.
• Pharmacoepidemiology uses real-world data from diverse populations under natural conditions. Drug intake and treatment monitoring are not controlled.

Populations Often Excluded From Clinical Trials

• Children
• Pregnant women
• Breastfeeding women
• Elderly patients
• Patients with multiple underlying health conditions
• Patients with genetic variations

Objectives of Pharmacoepidemiology Studies

• Describe characteristics of treated patients in real-world populations (usage patterns, dosages, etc.).
• Estimate drug safety and effectiveness in real-world situations.

Concept of Risk

• Risk is the probability that a specific event occurs within a period.
• The risk can be estimated using an incidence rate, which describes the number of new cases in a population over time.
• Risk varies according to time, place, and individual characteristics.
• Risk increases or decreases based on external factors.

Risk and Medications

• Exposure to a drug might be protective or detrimental.
• Some risks are predictable (related to known drug effects).
• Other risks are unpredictable (unexpected side effects).
• Some risks can be avoided (by modifying drug treatment).

Effectiveness of Medications

• Effectiveness describes a drug's ability to achieve desired results in real-world situations and heterogeneous populations.
• Health authorities require data to make informed decisions.

Why Study Effectiveness of Medications?

• Necessary for informed decision-making by health authorities.
• The data should be generalizable to current users to assess significant safety concerns.
• Health authorities, insurance companies, and hospitals rely on these studies.
• Industry benefits from an understanding for promoting medication adherence.

Types of Studies to Evaluate Effectiveness

• Comparative Effectiveness: Compare efficacy of two or more medications for the same condition.
• Association Studies: Identify the link between medication use and patient outcomes.

Impact of Effective Medication Studies

• May result in medication withdrawal due to harm.
• Changes to medication usage guidelines or contraindications.
• Changes in reimbursability.

### Conclusion of Pharmacoepidemiology

• Describes and estimates factors like drug use, risk, and effectiveness.
• Helps understand whether fundamental and clinical pharmacology findings are useful to patients in real life.

Bias in Observational Studies

• A major challenge in pharmacoepidemiology is bias in observational studies.
• Bias can lead to incorrect estimates of risk or effectiveness.

Types of Bias

• Selection Bias: Related to the inclusion of subjects in a study (different exposure rates, populations).
• Information Bias: Related to the quality of data collected (different data collection procedures among groups).
• Confounding Bias: Distortion of results caused by factors related to exposure and outcome, but not on the causal pathway.

Preventing Bias

• Careful study design (defining target population thoroughly).
• Use of appropriate tools.
• Controlling for factors that may influence results in study design and execution, such as data collection procedures, and treatment assignment.

Examples of Bias

• Non-response Bias: Participants in a study may differ from the population.
• Admission Bias (Berkson's Bias): Cases in a study are more likely to be hospitalized, leading to biased results.
• Recall Bias: Participants may have different memories of events or treatments depending on the study condition.
• Interviewer Bias: Interviewers may influence results due to differing questioning strategies.
• Indication Bias: The drug might preferentially prescribed to those at higher risk for a condition.
• Protopathic Bias: Treatment for early symptoms appears to cause the disease.

This quiz explores the fundamental concepts of pharmacoepidemiology, focusing on how medications impact population health. It covers various aspects including pharmacology and the efficacy of drugs in real-world scenarios, with emphasis on observational studies and clinical trials. Test your understanding of these important topics in drug safety and effectiveness.