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Pharmacoepidemiology - summary of all lectures
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Summary off all the lectures of the pharmacoepidemiology course at the Rijksuniversiteit Groningen.
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PharmacoepidemiologyLecture 1: Pharmacoepidemiology, Introduction (E. Hak)
Clinical questions:
1. DIAGNOSTICS: What is wrong?
2. ETIOLOGY: What is the cause
3. PROGNOSIS: What is the future of this patient?
4. INTERVENTION/THERAPY: What is the best treatment/how to prevent?
5. EFFICIENCY/ECONOMICS: How much does it cost?
Epidemiology: studies the occurrence of diseases in large populations of people as a function of
determinants. Epidemiology is an essential science for the conduct of ‘Evidence Based Medicine’.
Vaccination rate required is 94%
Process of drug development:
Drug discovery; how should the vaccine be made characterisation formulation; how to produce
at large quantities pre-marketing clinical trials; registration post-marketing
pharmacoepidemiologic studies economical evaluation.
Pharmaco-epidemiology: studies the contribution of drugs in disease prevention and therapy in large
populations.
Main reasons for dangerous side effects and withdrawal:
1. Clinical trials are not large.
2. Real world use of a drug differs trials are done in healthy people whereas the users will be
severely diseased.
3. Time plays a role trials have short duration while for some drugs you should use it for a
long time before a disease pops up.
4. Off-label prescribing may bring up unexpected issues e.g. for children.
Drug repurposing: drugs made for a disease have a positive effect on something else drug is used
for not for the initial purpose.
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,Typical post marketing research questions:
Drug X = the outcome of the study question. Patient Y = the study domain/hypothetical patient. Age
and sex are the determinants of the outcome.
Drug X = the determinant. Outcome Y = outcome. Disease Z = the study domain/hypothetical patient.
Types of epidemiological studies:
- Experimental studies: investigator determines what the participant is going to get.
RCT’s / community intervention trials / field trials.
- Observational studies: investigator has no influence on whether you get your vaccine.
Descriptive studies / case-control studies / cohort studies.
Randomised Control Trials (RCT):
- Narrow indications you want everyone to have the drug registered for a certain indication.
- Homogeneous population no people who with risks to avoid side effects.
- Small number trials not more than 5000.
- Randomisation computer determines who gets the vaccine or not, to avoid placebo.
- Double blinding patients and doctors don’t know who has the drug/placebo.
- Relatively short-term therapy trials are very expensive.
All of these trials lead to Evidence Based Medicine.
Observational trials (post marketing surveillance PMS
- Large numbers of patients
- Unlimited time of therapy.
- Drug-users in practice.
- Other influences (smoking, other drugs, nutrition)
RCTs is a really small part of the total patient population that is present. Whereas if you go to the
drug (post marketing) there is a much wider variation of people that is using it.
Important clinical information that has to be obtained in PMS research
- Usage and determinants in practice.
- Effects in daily practice (when combining with smoking/alcohol).
- Adverse effects.
- Drug interactions.
- New applications.
- Usage of the drug for other indications.
- Applied dosage and duration.
- Usage/effect in children/elderly and pregnant woman.
- Effect on hard endpoints (disease/mortality)
- Effect on population level.
- Costs.
- Compliance.
- Cost-effectiveness of interventions.
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,Terminology:
- Efficacy: effect in clinical trials or laboratory situations.
- Effectiveness: effect in daily practice.
- Efficiency: costs in relations to effects.
Post marketing surveillance (PMS): phase-IV study that monitors all desirable and undesirable
effects of drugs to human health, after these drugs are released on the market. The goal is to obtain
scientifically based data on rational and safe use of drugs.
Who has interest in PMS?:
- Patient wants 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.
Data sources for PMS:
- Spontaneous reporting systems.
Pharmacovigilance database Lareb pharmacists report any adverse effect that has
not been mentioned earlier.
- Routine databases (prescription/GP database).
- Questionnaires/interviews/web-based.
- Cohorts/physical testing/lab data.
Algemene verordering gegevensbescherming (AVG) / General Data Protection Regulation (GDPR):
privacy law that makes it much harder to get medical data from a patient (2018).
Pharmlines Initiative: to link the lifelines cohort study to the prescription data base IADB.
It does not matter much whether you take information from the GP or from the questionnaire
both resulted in more or less the same odds ratio.
ATC (Anatomical Therapeutic Chemical) system.
- Classification is done each year by the WHO. There are 7 positions and 5 hierarchical levels.
- e.g. N05BA01
- Coding can be different for the same drug different dosage forms.
Level 1: 1 letter anatomical main group.
Level 2: 2 digits therapeutic main group.
Level 3: 1 letter therapeutic subgroup.
Level 4: 1 letter therapeutic/chemical subgroup.
Level 5: 2 digits chemical substance.
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, Defined daily dose (DDD): average daily maintenance dose for a drug used for it’s main indication in
adults. Mainly used to quantify the volume of drug usage at the population level.
- Based on final phase registration trial just before registration.
- DDD does not contain patient information rough estimate.
- May vary by country.
- DDD of new drugs is revised after 3 years.
DDD lower than 1 the drug is not as effective as it should be.
DDD higher than 1 side effects.
Lareb: spontaneous reporting method.
- Things are reported such as: new adverse effects, severe adverse effects and new drugs.
- Pharmacists are the most importing cases into Lareb.
- Lareb will determine if there is a causal relation between the drug and the side effect. For
each report they make a causal association to determine whether a side effect is caused by
the drug or not.
- Naranjo algorithm: list of questions that give + of – points. Used for individual cases.
Bias in spontaneous reporting systems:
- Weber effect a drug that is new on the market leads to many adverse reports just because
it is new.
- Channeling phenomenon when drug therapies with similar indications are preferentially
prescribed to groups of patients with varying baseline prognoses.
Cohort studies advantages are:
- Fast.
- Large numbers.
- Validation data.
- Prevents recall bias.
- Information about reference group or controls without disease.
- Low costs.
- Minimal effort for the researcher.
Disadvantages of many observational studies:
- Indication bias.
- Insufficient number of patients.
- New drug (channeling).
- No information about confounding variables.
- Validity and completeness of data is dependent on the data source.
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