PHARMACOEPIDEMIOLOGY
LECTURE 1 – EPIDEMIOLOGY; AN INTRODUCTION
What is wrong? → diagnostics, cause of the disease? → Etiology, future of the
child? → prognosis, “best” treatment? → intervention/therapy, prevention? →
intervention/prevention, and price of prevention? → efficiency/economics.
“Epidemiology is the science that studies the occurrence of diseases in large
populations of people as a function of determinants.” It is an essential science for
the conduct of “Evidence Based Medicine”.
Etiology / Intervention Diagnosis / Prognosis
Causal associations Predictive associations
Analytic studies Descriptive studies
Case-control / Randomized Control Cohort design
Trials
Mostly 1 determinant More determinants
Confounding bias No confounding bias
Explanatory statistical model Predictive statistical model
Polio vaccine today: there are two vaccines
salk vaccine and sabin vaccin. It is part of
the worldwide children vaccination
program (DKTP in the Netherlands).
Pharmacoepidemiology is the scientific
field that studies the contribution of drugs
in disease prevention and therapy in large
population.
Fields of research in
pharmacoepidemiology:
- What proportion of the population is
using drugs/vaccines?
- Which determinants predict the use
of drugs/vaccines?
- Do drug/vaccines lead to a reduction
in diseased cases/mortality/increase
in quality of life?
- What type of and how many side
effects are caused by
drugs/vaccines?
Four main reasons for dangerous side effects and withdrawal
1. Clinical trials are not large
2. “Real world” use of drug differs
3. Time plays a role
4. Off-label prescribing may bring up unexpected issues
The pre-clinical phases mainly consist of synthesis of the drug and animal
experiments. The clinical phases are divided in three phases. The phase IV
studies are post-marketing and are of interest for pharmaco-epidemiologists.
Typical research question for post-marketing studies:
, 1. What is the use of drug X and patient Y and what is the variation between
age and sex?
2. What is the effect of drug X in the treatment of disease Z on outcome Y?
(bold = outcome, cursive = study patient, underlined = determinants)
Epidemiological studies are divided in experimental studies (clinical trials
(RCTs), community intervention trials, and field trials) and observational
studies (descriptive studies/cross-sectional studies, case-control studies, and
cohort studies). In observational studies it is not decided what a patient will get,
these are diagnostic and prognostic research questions.
Experimental
- Narrow clinical indications
- Homogenous population Population
- Small number
- Randomized and controlled Determinant / exposure
- Double blind and relatively short-term therapy Outcome
In observational studies there are large
number of patients, unlimited time, drug-
users in practice, and other influences are
present, like smoking, other drugs, and
nutrition.
Important clinical information that has to be
obtained from PMS research:
- Soft endpoint: Quality Adjusted Life
Year (QALY)
- Effect on population level is
specifically important for infections which have a person-to-person
transmission.
Efficacy → effect in the clinical trials or laboratory studies
Effectiveness → effect in daily practice
Efficiency → costs in relation to effects
In post-marketing surveillance all (anticipated and unanticipated) desirable and
undesirable (adverse)-effects of drug to human health are monitored, after these
drugs are released on the market.
Who have interest in PMS?
- Patient: wants an effective and safe drug with reliable
information
- Physician/pharmacist: wants reliable and complete information to make
a good decision
- Insurance company: importance of rational prescribing with regard to
costs
- Government: registration and safety
- Industry: wants a good product
, Information sources for PMS are
spontaneous reporting systems
(LAREB), routine (administrative)
databases,
questionnaires/interviews/web-
based, and cohorts/physical
testing/lab data.
Considerations pharmacists have to
take into account: privacy, indication
is not available, patient data is limited,
self-medication, compliance, adverse effects, history, good information about
medication (dosage, duration, what drug).
Patients considerations: privacy, completeness, reliability, adverse effects,
smoking, alcohol. These are question techniques to prevent these problems →
timing of interview or questionnaire.
ATC system
- Anatomical Therapeutic Chemical
classification system
- Classification of disease in a manner
similar to: ICPC-9, ICPC010, or
ICD9/ICD10
- There are 7 positions in 5
hierarchical levels
N1: 1 letter anatomical main
group
N2: 2 digits therapeutic main
group
N3: 1 letter therapeutic subgroup
N4: 1 letter therapeutic/chemical subgroup
N5: 2 digits chemical substance
DDD system
- Defined Daily Dose
- It is the average daily maintenance dose for a drug used for its main
indication in adults
- It is a rough estimate in which there is no patient information
- Every three years the DDD is revised
DDD’s are mainly used for the quantification of the volume of drug usage at the
population level:
- The number of DDD’s per 1000 persons per day (for example in a nursing
home or country)
- The number of DDD’s per 100 bed-days (for example in a hospital)
- The number of DDD’s per day (in a nursing home or hospital)
- The costs per DDD for a drug (comparison between the costs of two drug
for the same indication)
If the DDD is below 1: there is little or no therapeutic effect. If the DDD is much
higher than 1 adverse effects will occur.
Adverse events are reported to the LAREB and it follows the Yellow Card System
from the UK. Reported are:
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