Pharmacoepidemiology is the one of branch deals with distribution of diseases and outcome measurement, etc.

1. A M E ENA K A DA R K A
S E C OND S E M, M P H A RM
D E P T . O F P H A RMACY P R A C T I CE
S A NJO C O L L EGE O F P H ARMACEUT I CAL S T UDI ES
INTRODUCTION TO
PHARMACOEPIDEMIOLOGY

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INTRODUCTION
 Epidemiology is the study of occurrence, distribution and determinants of health and
diseases or disorders in man and its application in controlling health problems.
 Epidemiology has by tradition two major areas.
 First is the study of infectious diseases that spread to large populations, i.e., epidemics.
 The second is the study of chronic diseases.
 Epidemiological studies help to solve such health problems and provide a basis for
improving living conditions of the people.
 During its progress and development, epidemiology has made available precise and
strict methodologies for the study of diseases.

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 Pharmacology is the study of the effects of drugs.
 Clinical Pharmacology is the study of the effects of drugs in humans, It is traditionally
divided into two basic areas namely:
1. Pharmacokinetics
2. Pharmacodynamics.
 Pharmacokinetics is the study of the relationship between dose administered of a drug
and the serum or blood level achieved, it deals with absorption, distribution, metabolism
and excretion.
 Pharmacodynamics is the study of the relationship between drug level and drug effect.
 Clinical pharmacology helps one to predict the effect in a patient after administering a
certain drug regimen.

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 Pharmacoepidemiology encompasses elements of both these fields, exploring the effects
achieved by administering a drug regimen.
 The core of pharmacoepidemiology lies at the intersection of epidemiology and clinical
pharmacology.
 The contemporary activities of the pharmacoepidemiology has three aspects in its
coverage:
1. Epidemiology
2. Clinical Pharmacology
3. Clinical Pharmacy.

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PHARMACOEPIDEMIOLOGY
 Epidemiology is the study of the distribution and determinants of diseases in
populations.
 Epidemics is the study of chronic/ infectious diseases in large populations.
 Pharmacoepidemiology is the study of the use of and the effects of drugs in large
number of people.
 It involves the examination of a single individual or large groups of people followed for
many years.
 It involves gathering & analysis of information in order to identify possible causation &
related factors, that can be applied in clinical practice to group of people & also to
individuals undergoing treatment.

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 It applies the principles of clinical pharmacology, clinical epidemiology and
biostatistics.
 The Pharmacoepidemiological studies concentrate on the period after the drug enters
the market known as Post Market Surveillance (PMS) period.

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NEED OF PHARMACOEPIDEMIOLOGY
 Lack of alternative models to investigate some drug events
E.g.: to evaluate teratogenic effects of a new medicine
 Clinical Trials (CTs) are inadequate to answer questions about drug safety, as they lack
adequate statistical power.
 If at all adequate for establishing effectiveness, the sample size are inadequate to detect
less common ADRs.
 CTs are conducted on highly selected patients without any co-morbidities & who
taking no other medications.
 CTs does not involve elderly, pediatric or pregnant patients.
 CTs investigate the single indication, hence, CTs fail to provide adequate information
related to safety & efficacy of a drug under non-trial conditions & in other indications.
 Pharmacoepidemiological models provide alternative approaches to evaluate drug
effects.

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AIMS OF PHARMACOEPIDEMIOLOGY
 Pharmacoepidemiological studies are concerned with two main aspects:
i. The study of adverse effects of drugs
ii. The appropriate use of medicines.
 Pharmacoepidemiological studies focus on,
 Global trends in prescribing
 Appropriateness of drug use
 Medication adherence
 Lifestyle effect on drug therapy
 Special population on drug therapy
 Drug interaction
 Predictable ADRs

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 Aims:
1. Signal Generation
2. Risk Quantification
3. Hypothesis Testing
Signal Generation
 The term signal is used in ADR reporting and Pharmacovigilance as an early warning in
the case of ADRs.
 Signal is a reported information on possible causal relationship between adverse event
and a drug or medicine.
 Helps to identify new application of existing drug
 Eg: Aspirin – first used for pain & inflammation later used in cardiac diseases due to
blood thinning property.
 Minoxidil is used as Antihypertensive and Hirustism.

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 It is the process of evaluating risks that have been identified and developing the data for
other purposes like making decisions on other occasions.
 Various measures of the risk are used in Pharmacoepidemiology to quantify the
probability of experiencing an adverse outcome capture the relative increases in risk
between treated and untreated populations.
 Various measures of risk includes:
 Cumulative incident
 Incident rate
 Relative risk
 Odds ratio.
Risk Quantification

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 It involves use of comparison group to determine whether there are differences in
variable of interest (risk factor, trait, characteristic or drug exposed)
 Statistical methods are used to assess whether the observed difference occurred by
chance.
 It gives a conclusion about relationship between exposure to a drug and clinical event.
Hypothesis Testing

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APPLICATIONS
1. Estimation of the risks of drug use
2. Use in patient counseling
3. Formulation of public health policy decisions
4. Facilitation of pharmacoeconomic evaluations
5. In pharmacovigilance
6. To carry out drug usage analysis
7. Formulation of therapeutic guidelines
8. Health outcomes research.

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1. Estimation of the risks of drug use:
 The risk involved in drug use can be quantified.
 The benefits & risks of use of a drug may be weighed.
 Risk estimation also helps to identify risk situation
Ex: Case reports of triazolam induced psychiatric disturbances appeared soon after
its introduction to market. The drug was withdrawn in some countries. The reaction
was likely due to dose related, hence the problem was abated by recommending a
lower dose.

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2. Use in patient counseling:
 Collection & analysis of observational data from other studies may help to address
certain issues through counseling the patients.
Ex: A pregnant patient may wish to terminate pregnancy if there is a substantial risk
for producing a seriously malformed child, but would also wish to proceed with the
pregnancy if the risk is low.

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3. Formulation of public health policy decisions:
 Qualitative as well as quantitative information from Pharmacoepidemiological studies
helps to address many issues.
 Ex: If an inappropriate prescribing is observed among prescribers, regulatory agencies
may require educational intervention or may impose restrictions on specific drugs or on
practitioners.
 Pharmacoepidemiological studies also helps the policy makers to assess whether a drug
should be withdrawn from the market or allowed to remain.

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4. Facilitation of pharmacoeconomic evaluations:
 Data from Pharmacoepidemiological studies can be used to measure the effects of drugs
on overall health care costs & resource consumption.
 Ex: Hospitalization due to serious adverse effects of a drug leads to more expenses as
well as resource consumption, which could be avoidable.
5. In pharmacovigilance
 Pharmacoepidemiological studies are useful to monitor ADR and find out incidence and
risk/benefit of drug.
 Prevention and reduction of occurrence of ADR.

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7. Formulation of therapeutic guidelines:
 PE studies helps to examine the effectiveness of drugs in elderly & pediatric patients
and also in patient with co morbidities.
 From these data therapeutic guideline can be prepared.
8. Health outcomes research:
 Investigating the impact of medications on patient outcomes, such as mortality,
morbidity, quality of life, and healthcare utilization.
6. To carry out drug usage analysis
 Used to identify over usage, under usage and non-usage of medicine in population
 Medicine usage pattern are studied on a set of population.

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Other applications of PE studies include:
Pharmacogenomics studies: helps to identify focus area of
pharmacogenomics study
Age based medicine use and its analysis
Evaluation of hospital committee
Generation of database for other studies.

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Outcome measurement:
 It is defined as the systematic quantitative analysis of outcome indicator at a point
of time.
 These measures are used to find out whether the goal of the patient, are identified and
achieved.

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OUTCOME MEASURES
 Measuring outcomes is an important component for management of individual
patient by collectively comparing care and determining effectiveness.
 The use of standardized tests and measures early in an episode of care establishes the
baseline status of the patient/client, providing a means to quantify change in the
patient's/client's functioning.
 Outcome measures, along with other standardized tests and measures used throughout
the episode of care, as part of periodic reexamination, provide information about
whether predicted outcomes are being realized.

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 Clinical outcome assessments (COAs) measure a patient’s symptoms, overall mental
state, or the effects of a disease or condition on how the patient functions.
 COAs can be used to determine whether or not a drug has been demonstrated to
provide treatment benefit.
 Treatment benefit can also be defined in terms of a safety benefit compared to other
treatments.
Types of COA measures:
Patient-reported outcome (PRO) measures
Clinician-reported outcome (ClinRO) measures
Observer-reported outcome (ObsRO) measures
Performance outcome (PerfO) measures.

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Outcome measures include studies on:
• Functional status (level of functioning, Supervision required, ability to work)
• Symptom status (days free of pain / an event)
• Patient satisfaction with various aspects of care (delivery of care, effects on daily
activities or life satisfaction) and
• Quality of Life (QOL)studies
 The therapeutic outcomes may be classified as cure, improvement, no change or
deterioration.
 On the other hand, they can be classified as success or failure.

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GOALS OF MEASURING CLINICAL OUTCOMES
 Improve the patient experience of care.
 Improve the health of populations.
 Reduce the per capita cost of healthcare.
COMMON OUTCOME MEASUREMENT
 Morbidity: Measured as the number of cases of disease or events that occur per unit of
population (per 100), unit of time (per year) or both.
 Mortality: Deaths occurring due to transmission of a disease or due to or prevented by
the use of drugs
 Readmission
 Safety of care
 Patient experience
 Effectiveness of care
 Timeliness of care
 Efficient use of medical imaging.

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METHODS OF OUTCOME MEASUREMENT
1. STATISTICAL METHODS
2. DRUG USE METHODS
1. STATISTICAL METHODS
a) PREVALENCE:
 It is the proportion of people affected with a disease or exposure to a particular drug in
a population at a specific period of time.
 It is usually determined by surveying the population of interest.
 It is a census type of measure, indicating how frequently a disease is at a period of
time.
 It varies between 0-1, expressed as %.

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Uses:
 Estimate the magnitude of health (or) disease problem in the community
 To identify the potential high risk population community
 Useful for administrative & planning purpose.
Prevalence = No. of population with disease at a given time
Total no: of population at a given time
b) INCIDENCE :
 It is a measure of the risk of developing some new condition within a specified period
of time.
 It is better expressed as a proportion or as a rate.

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i. Cumulative incidence (CI):
 It is a no. of new cases within a specific period of time, divided by the size of
population initially at risk.
 It is used for the measure of the risk of disease or probably the probability of
developing the disease during specific period.
 Normally, it is measured with an inception cohort, that is large group of population is
observed over a period of time, and the no: of cases or outcomes measured.
CI = No. of new cases of disease (or) injury during specific period
Size of population at start of period

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ii. Incidence rate:
 It is the no. of new cases per population at risk in a given period of time.
 It describes the probability of a new case occurring during a given time interval.
IR = No: of new cases of diseases (or) injury during specific period
Total time each person was observed
Relationship Between Prevalence And Incidence
P = I × D
where,
P: Prevalence
I : Incidence
D: Duration
 Longer the duration of disease, greater the prevalence.

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REFERENCES
1. A Textbook pf Pharmacy Practice, K G Revikumar, Revised second edition. Page No:
367- 391.
2. www.PharmaDost.info
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