Pharmacoepidemiology

Dr. Haripriya UppalaPost GraduatePharmacology

S.V.M.C

Source

• ISPE – International Society of PharmacoEpidemiology webite - http://www.pharmacoepi.org

• Drug Benefits and Risks: International Textbook of Clinical Pharmacology-By Christoffel Jos van Boxtel, Budiono Santoso, I. Ralph Edwards

• Internet – various websites.

Pharmacoepidemiology

Clinical Pharmacology Epidemiology

“The study of the use and effects of medications in large

numbers of people”

Strom

“The application of epidemiologic knowledge, methods, and reasoning to the study of the effects (beneficial

and adverse) and use of drugs in human populations.”

Porta & Hartzema

“The study of drugs as determinants of health and disease in the general unselected population.”

Spitzer

History and evolution

1906

The initial drug-oriented law in U.S.

“Pure Food and Drug Act“ (Wiley act)

Pillar of progressive eraIllegal to manufacture adulterated

or misbranded foods or drugsNo evidence/proof regarding

safety/efficacy required.

CHANGE IS A GOOD THNING- Theodore Roosevelt

1937

Taste of Raspberries, Taste of DeathThe 1937 Elixir Sulfanilamide Incident• 1932: 1st sulfa drug• Elixir of Sulfanilamide – chemist Watkin’s

creation, a liquidated sulfanilamide for children.• 10% sulfanilamide, 72% diethylene glycol (DEG),

16% water, “elixir flavor”, raspberry extract, saccharin solution, amaranth, and caramel.

• 107 deaths, 208 survivors.• Cause of death – Renal failure.

1938: Food, Drug & Cosmetic (FD&C) Act

• Requires new drug pre-marketing safety studies – Origin of what is now the pharmacoepidemiology

• Prohibits false therapeutic claims• Authorizes factory inspections• Allows FDA to request court injunctions (previously:

only seizures & prosecutions)• Extends control to cosmetics and devices• Requires safe tolerances for unavoidable poisonous

substances

1961

Thalidomide tragedy

• introduced in the 1960s• marketed as Contergan®• used to control nausea in pregnancy• reports of limb abnormalities

Dr. William McBride of Australia reported increased frequency of birth defects (seal limbs) with thalidomide usage, that left 10,000 babies disabled for life.

• Kefauver-Harris Amendments• “Proof of Efficacy” required • Adverse events reporting to FDA

required• “Informed consent” for clinical

studies • Drug ads must disclose side effects • 2-year inspection mandate

The Vioxx® controversyFirst reports of MI in VIGOR 2007 Confirmed by cohort studyPublished in the Lancet400K Medicaid patientsÎ in risk of MINeed for post-marketing drug studies

• Recent data indicate that 100000 Americans die each year from Adverse Drug Reactions, and 1.5 million US hospitalizations each year result from Adverse Drug Reactions; yet, 20-70% of Adverse Drug Reactions may be preventable. The harm that drugs can cause has led to the development of the field of pharmacoepidemiology.

In INDIA ???????

No sufficient data till date

Pharmacoepidemiology

• All drugs have adverse effects. • Pharmacoepidemiology will never succeed in

preventing them. • It can only detect them, hopefully early, and

thereby educate health care providers and public, which will lead to better medication use.

• The net results of increased activity in Pharmacoepidemiology will be better for industry and Academia but most importantly, for public’s health.

• Pharmacoepidemiology can minimize its adverse public health impact by detecting it early.

• At the same time, it can improve the use of drugs that have genuine role, protecting against the loss of useful drugs.

• Pharmacology is the study of the effect of drugs; and clinical pharmacology is the study of effect of drugs in humans.

• Part of the task of clinical pharmacology is to provide a risk benefit assessment for the effect of drugs in patients.

• Doing the studies needed to provide an estimate of the probability of beneficial effects in populations, or the probability of adverse effects in populations and other parameters relating to drug use may benefit from using epidemiological methodology.

• Epidemiology = Epi(on the) demos(people) logos(study)

• Epidemiology can be defined as the study of the distribution and determinants of diseases in populations.

• Epidemiological studies can be divided into two main types:

Observational VS Experimental studies

• Observational studies , Allow nature to take its cause; the investigator measures but does not intervene.

• Descriptive study: focuses on the description of the occurrence of a disease in a population.

• Analytical study analyses relationships between health status and other variables.

• Experimental or interventional studies: involve an active attempt to change a disease determinant(e.g an exposure or a behaviour) or the progress of a disaese (through treatment)

• The studies are based on a group which has had the experience compared with control group which has not had the experience.

Purpose of descriptive epidemiology

• To generate hypothesis• To permit evaluation of trends in health &

disease and comparisons among countries and subgroups within countries.

• To provide a basis for planning, provision and evaluation of health services

• To identify problems to be studied by analytical methods and to suggest areas that may be fruitful for investigation.

Case reports

• Documents unusual medical occurrences• Can represent the first clues to the

formulation of hypothesis• Generally report a new or unique findings • Previous undescribed disease.

• Eg; Zappacosta presented a case report of a patient treated with minoxidil that was discovered to stimulate the hair growth.

• Subsequently a topical formulation of minoxidil was developed to take advantage of that effect

Case series

• Collection of individual case reports which may occur within a fairly short time

• Experience of a group of patients with similar diagnosis.

• Eg: Krishnamoorthy and king reported on the adverse effects associated with the use of olanzapine in 5 children with severe behavioural problems.

• Adverse events includes: wt. gain(3/5 children)sedation(2/5 children) and akathisia (2/5 children).

Case series

AdvantagesUseful for hypothesis generationInformative for very rare disease with few

established risk factorsUsually of short duration.

DisadvantagesCannot study cause and effect relationshipsCannot assess disease frequency

Cerivastatin (Baycol), an effective and inexpensive lipid lowering drug, was introduced in 1997. It was removed from the market in 2001 because of reports of fatal cases muscle breakdown (rhabdomyolysis).

Ecological Study

• Obtain group-level exposure information and disease prevalence at the same point of time.

Ecologic Studies: Breast Cancer Incidence

by National Fat Intake

0

50

100

150

200

250

500 700 900 1100 1300 1500 1700

Fat intake (kcal/d)

Inci

denc

e pe

r 100

,000

p-y

Cross-sectional study• It is also called epidemiologic study or prevalence study.• It analyses (describes)data collected on a group of

subjects at one point in time rather than over a period of time. i.e. they survey exposure and disease at a single point in time.

• Both exposure and outcome variables are been evaluated at the same point in time(without any inbuilt directionality).

• Most sophisticated descriptive study.

• It answers the question “WHAT IS HAPPENING RIGHT NOW?”

• Eg: cross-sectional studies was published by Dua and colleagues, who examined inappropriate sale of antibiotic use in pharmacies in Nagpur.

Such studies can identify problem areas and suggest where remedial action should be directed

Cross-sectional studies

Advantages

• Best for determining the status

(prevalence)• Quick• Relatively inexpensive

Disadvantages• Only a snapshot at a time

leading to a misinformation• Response rate may be

low ,with result not representative of the population

Correlational study designs

• A study comparing incidence/prevalence of one event against another on a global scale

• Measures that represent characteristics of entire populations are used to describe the disease in relation to some factor of interest (such as age, calendar time, food consumption, drug use and utilization of health services)

Correlational study designs

Advantages• Compares events among

nations.

Disadvantages• Doesn’t compare

individuals, so it might lead to overgeneralization.

Analytical studies

Two basic designs:• Case – control or retrospective study• Cohort or prospective

• NOTE• There must be a comparison group• No control No conclusion(NCNC)

Case control or case history study

Advantages of case control studies

• Relatively easy to carry out.• Rapid and inexpensive.• Requires comparatively few

subjects.• Can assist one in studying

different etiological factors.• Does not need an ethical

clearance.• No risk to the subject .

Disadvantages of case control studies

• Introduces bias• To select an appropriate

control could be difficult • It may be difficult to

distinguish between the cause of a disease and an associated factor

Cohort study

• A cohort is a group of people who have something in common and remain part of a group over an extended time

• A group of people exposed to a suspected etiological agent are compared with a matched control who have not been similarly exposed. Subject selected on the basis of exposure [a etiological factor; cigarette smoking]

• Follow-up over a period to compare the outcome• aka Longitudinal study or Prospective study

Cohort Study design

Advantages

• No bias• Risk can be calculated bcos

the incidence can be calculated

• Effective for studying rare exposures

• Allows the study of the natural history of the disease

• Assists in determining the temporal relationship between the etiological factor & the disease

Disadvantages

• Takes a long time • Expensive• Large no of subjects are

needed• There could be changes in

the standard methods or diagnostic criteria

Experimental studies

• Studies in which 1 group is deliberately subjected to an experience compared with a control group with no similar experience

• The gold standard in medicine because it proves causality

• Can be controlled or uncontrolled

Experimental / intervention studies

Uncontrolled experimental studies

• Intervention is not compared with a control

• The aim is to confirm that the Intervention made a difference

Uncontrolled experimental studies

• In this study, a drug or procedure is compared to:

1. Another drug2. Procedure3. Placebo4. Previously accepted tx• The aim is to prove the

difference due to tx

Uncontrolled experimental studies

• Control could be:• Blind trial-single or double

A. METHODOLOGY1. Concurrent or parallel: randomized or non-

randomized(quasi)2. Sequential control: self controlled or cross over3. External control

Study population

1. Clinical trials2. Field trials3. Community trials

Experimental studies

Advantages• Best study type• Greatest proove of causality• Gold standard for other

design• Least bias• Proves best tx or procedure

efficacy

Disadvantages• Greatest expense • Long duration• Unproven facts adopted by

community can hinder study acceptance

Drug utilization study

• Aims to evaluate factors related to the prescribing, dispensing, administering and taking of medication, and its associated events (either beneficial or adverse).

• Since the early 1960’s the interest in Drug Utilization Studies has been increasing, first with market-only purposes, then for evaluating the quality of medical prescription and comparing patterns of use of specific drugs.

• The increasing importance of drug utilization studies as a valuable investigation resource in pharmacoepidemiology has been bridging it with other health related areas, such as public health, pharmacovigilance, pharmacoeconomics, eco-pharmacovigilance or pharmacogenetics.

• Drug utilization research is thus an essential part of pharmacoepidemiology as it describes the extent, nature and determinants of drug exposure. In common use, the distinction between these two terms has become less sharp, and they are sometimes used interchangeably.

Insights into the following aspects of drug use and drug prescribing

• Pattern of use: • extent and profiles of drug use• trends in drug use and costs over time.• Quality of use: Audits comparing actual use to national and regional prescription guidelines

or local drug formularies. Quality indices of drug use may include the• choice of drug • drug cost • drug dosage • drug interaction awareness• ADR awareness• proportion of patients being aware of/unaware of the cost/benefit of the

treatment, etc.

Special applications of Pharmacoepidemiology

• Studies of Drug Utilization•Evaluating and improving physician prescribing•Drug Utilization Review • Special methodologic issues in PE studies of Vaccine Study•PE studies of Devices• Studies of Drug induced birth defects•PE and Risk management•Use of PE to study Medication Errors•Hospital PE

Impact of pharmacoepidemiology

• population based drug related studies• rare drug adverse events• drug efficacy• drug interactions• patterns of use

Studying drug interactions in pharmacoepidemiology

– drug interaction studiesusually small human studiesin vitro studiessoft end-points– usually look at soft outcomes– clinical significance of interaction-unknownEg., cimetidine vs. P-450 inhibition not all interactions clinically significant

Drug interactions in pharmacoepidemiology

• case-control study by Juurlink (JAMA;2003)• looked at interaction between1. cotrimoxazole+glyburide----hypoglycemia 2. clarithryomcin+digoxin ---- digoxin toxicity3. K+sparing diuretics+Ace-inhibitors-- hyperkalemia • used the ODB data using 1.5 million older adults• 7 years time span • matched for age, sex, medication, renal disease,

comorb

Bias in pharmacoepidemiology

• Bias -- Systematic error in research

• Types of bias

1. Recall bias -- difficulty recalling drug

2. Selection bias -- one group different than another

3. Channeling bias --- drug prescribed to sicker patients

4. Misclassification bias ---- Either disease or drug misclassified

Pharmacovigilance• A type of continual monitoring for unwanted

effects and other safety-related aspects of drugs that are already on the market. In practice

• Spontaneous reporting systems which allow health care professionals and others to report adverse drug reactions to a central agency.

• The central agency can then combine reports from many sources to produce a more informative safety profile for the drug product than could be done based on one or a few reports from one or a few health care professionals.

Clinical Pharmacology

Epidemiology &Biostatistics

PharmacovigilanceDrug utilisation studies

Pharmacoeconomics& Pharmacogenomics

The gem cannot be polished without friction, nor medicinesperfected without trials.

– Chinese proverb.