Different outcome measures in Pharmacoepidemiology includes monetary units, no. of prescriptions, DDDs, PDD, etc.

1. A M E E N A K A D A R K A
S E C O N D S E M M P H A R M
D E P T . O F P H A R M A C Y P R A C T I C E
S A N J O C O L L E G E O F P H A R M A C E U T I C A L S T U D I E S
DRUG USE MEASURES

2. 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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3. GOALS OF MEASURING CLINICAL OUTCOMES
 Improve the patient experience of care.
 Improve the health of populations.
 Reduce the per capita cost of healthcare.
METHODS OF OUTCOME MEASUREMENT
1. STATISTICAL METHODS
2. DRUG USE METHODS
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4. DRUG USE MEASURES
 It includes the pattern of use of drugs for a specific diseases/ in a
group of people.
 Different types of drug use measures are
1. Monetary units
2. Number of prescriptions
3. Units of drug dispensed
4. Defined daily doses
5. Prescribed daily doses
6. Medication adherence measurement 4

5. MONETARY UNITS
 It is the most common and generally used practice in estimation of drug use
is to quantify the value of medicine in monetary units like rupees, dollar
etc.
 It helps to find the percentage of financial burden for individuals, family,
society, organization or governments for drug use.
 Applicable for the comparisons at various level from person to global.
 Monetary units are convenient and can be converted to a common unit, which
then allows for comparison.
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6.  The disadvantage is quantities of drugs actually consumed are not known
& prices may vary widely.
 Eg: A Paracetamol tablet may cost 1 rupee in India can have a cost of 5
rupee in the middle east countries and 15 rupees in USA.
 In such a situation the measurement of drug use in monetary units may not
help to give a clear picture when countries are compared.
 However it is useful in comparing within a similar set up.
 Similarly adrug may have different dosage forms and strengths in market
and price may vary for them.
 Unless corrective measures are taken there can be errors while
estimating the monetary value of drug use.
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7. NUMBER OF PRESCRIPTIONS
 It is used in research due to the availability & ease.
 Prescription number analysis is used to get rough estimates like
percentage of analgesic drugs, oral contraceptives or antibiotics used by
the population.
 It helps to give comparatively good estimates of no. of peoples exposed to a
certain drug.
 These studies help to find whether there is increase in the number of
prescriptions during certain periods.
 Disadvantage: Quantities dispensed vary greatly as duration of treatment
increases. 7

8. UNIT OF DRUG DISPENSED
 Units of drug dispensed like tablets, vials is easy to obtain and can be used
to compare, usage trends within the population.
 It helps to analyse drug use trend in various countries, state or territories.
 The unit dose system of medication distribution is a pharmacy coordinated
method of dispensing and controlling medications in organized health-care
settings.
Units of
Drug
Dispensed
Automation Manual
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1. AUTOMATED MEDICATION DISPENSING CABINETS
 Special electric cabinets are setup in the pharmacy.
 Technicians play a key role to maintain appropriate inventory and make
frequent adjustments.
 Addition and deletion of the drug in the pharmacy can be indicated
electrically in a automated manner.
 By this method the utilization of drugs outcome can be found easily.
2. MANUAL CART-FILL PROCESS
 It requires the medication carts or cassettes.
 In front of the patient bed case sheet the treatment chart is attached in dual
form, one for dispensing the drugs by the pharmacist and one for the nurse to
dispense drugs.
 Pharmacist then dispenses the drugs in bed side to the patient and notes the
drugs that are being dispensed to the patients.

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 The disadvantage is that no information is available on the quantities actually
taken by the patients.
 Hence difficult to determine the actual number of patients exposed to the
drug.

11. DEFINED DAILY DOSES (DDD)
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 Defined Daily Doses (DDD) are the assumed average maintenance dose per
day for a drug used for its main indication in adults.
 DDDs are only assigned for medicines given an ATC codes (Anatomical
Therapeutic Chemical )
 The DDDs are allocated to drugs by the WHO Collaborating Centre in Oslo,
working in close association with the WHO International Working Group on
Drug Statistics Methodology.
 Only one DDD is assigned per ATC code and route of administration (e.g. oral
formulation).
 The DDD is sometimes a dose that is rarely or never prescribed because it is
an average of two or more commonly used doses.

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 It is normally expressed as DDD/1000 patients per day (or) DDD/100 bed per
day.
 Drug usage (in DDDs) = Item used × Amount of drug per item
DDD
 Eg: A patient has taken Paracetamol as analgesic. It is having DDD=3g i.e.
average patient who uses Paracetamol 3 g in a day (or) within a period of 24
hours.
This is equivalent to 6 standard tablets of 500mg each.
If patient consumes 24 such tablets.
Drug usage (in DDDs) = 24(items) × 500(mg/item)
3000 mg
= 4

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 DDDs are not established for all medicines with an ATC code.
 Major drug groups without DDDs are: -
 Topical products
 Sera
 Vaccines
 Antineoplastic drugs
 General/local anaesthetics
 Ophthalmological / ontological
 Allergen extracts
 Contrast media.

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 The DDD is a unit of measurement and does not necessarily correspond to the
recommended or Prescribed Daily Dose (PDD).
 Therapeutic doses for individual patients and patient groups will often differ
from the DDDs, as they will be based on individual characteristics such as
age, weight, ethnic differences, type and severity of disease, and
pharmacokinetic considerations.
 ADVANTAGES:
 Its usefulness in working with readily available drugs statistics and allows
comparison between drugs in same therapeutic classes.
 DISADVANTAGES:
 Doses may vary widely : Eg: antibiotics.

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 APPLICATIONS OF DDDs
 Examine changes in drug utilization over time
 Make International comparisons
 Evaluate the effect of an intervention on drug use
 Document the relative therapy intensity with various groups of drugs
 Follow the changes in the use of a class of drugs
 Evaluate regulatory effects & effects of interventions on prescribing
patterns.

16. PRESCRIBED DAILY DOSES (PDD)
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 The prescribed daily dose (PDD) is defined as the average dose prescribed
according to a representative sample of prescriptions.
 The PDD can be determined from studies of prescriptions, medical or
pharmacy records, and it is important to relate the PDD to the diagnosis on
which the drug is used.
 The PDD will give the average daily amount of a drug that is actually
prescribed.
 Useful for validating the defined daily dose (DDD)
 Pharmacoepidemiological information (e.g. sex, age and mono/combined
therapy) is also important in order to interpret a PDD.

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PDD vary according to:
 Illness treated
 National therapeutic tradition
 Between different countries.
For example, the PDDs of an anti-infectives may vary according to the severity
of the infection
 There are also international differences between PDDs, which can be up to 4 or
5 fold higher/lower.
Eg: PDDs in Asian populations are often lower than in Caucasian populations.

18. MEDICATION ADHERENCE
MEASUREMENTS
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MEDICATION ADHERENCE
 It is defined as the extent to which a patient’s medication-taking behavior
coincides with the intention of the health advice.
 Medication adherence is one of the most important factors that determine
therapeutic outcomes, especially in patients suffering from chronic illnesses.
 Whatever the efficacy of a drug, it cannot act unless the patient takes it.
 Adherence to treatment is the key link between treatment and outcome in
medical care.

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TYPES OF MEDICATION NON-ADHERENCE
 Normally patients tend to miss the medication dose due to various reasons
is termed as Medication non-adherence.
Medication
non-
adherence
Primary non-
adherence
Secondary
non-
adherence
Intentional
non-
adherence
Unintentional
non-
adherence

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1. Direct – objective
 Measure blood or urine levels of drugs – gives indication of short-term
adherence, unless the drug has a long half-life
 Measure blood levels of marker – add marker to medicines and measure
levels in the body. The ethical issue of the safety of the given marker is a
matter of concern. For example, low-dose Phenobarbitone gives both
quantitative and qualitative data over the preceding few weeks with little
intra and inter individual variation.
2. Indirect – objective
 Pill count – count the tablets remaining in the container. Vulnerable to
overestimates of adherence.
 Prescription refill – accurate data monitoring system required.
 Electronic medication containers – opening and closure times of container
recorded on a microprocessor in the lid of the container.

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3. Health outcome measures – assessing therapeutic efficacy, for example,
blood pressure control, asthma severity, survival, hospitalization, etc.
 Clinic attendance – opportunity to counsel patients. Clinic non-attenders are
more likely to be non-adherent.
 Appointment making
 Appointment keeping
 Preventive visits
4. Indirect – subjective (methods of questionable reliability)
 Patient interview – asking patients if they have adhered to the prescribed
regimens
 Diary keeping.

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MEDICATION ADHERENCE MEASUREMENT
1. Biological Assays
 Biological assay measure the concentration of a drug, its metabolites, or tracer
compounds in the blood or urine of a patient.
 These measures are intrusive and often costly to administer.
 Patient who know that they will be tested may consciously take medication
that they had been skipping, so the tests will not detect individuals who have
been non adherent.
 Drug or food interactions, physiological differences, dosing schedules, and the
half-life of the drugs may influence the results.
 Biological tracers that have known half lives and do not interfere with the
medication may be used, but there are ethical concerns.
 All of these methods have high costs for the assays that limit the feasibility of
these techniques.

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2. Pill Counts
 Counting the number of pills remaining in a patient’s supply and calculating
the number of pills that the patient has taken since filling the prescription is
the easiest method for calculating patient medication adherence.
 Some data indicate that this technique may underestimate adherence in older
populations.
 Patterns of non-adherence are often difficult to discern with a simple count of
pills on certain date weeks to months after the prescription was filled.

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3. Weight of Topical Medications
 The weight of a topical medication remaining in a tube is used as a measure of
adherence.
 When compared with patient log book of daily medication use, weight
estimate of adherence were considerably lower than patient log estimates.
 In the clinical trials involving topical applications incorporate medication
weights as the primary measure of adherence.
 In a comparison of methods to measure adherence, found that estimates
calculated from medication logs and medication weights were consistently
higher than those of electronic monitors.

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4. Electronic Monitoring
 The Medication Event Monitoring System(MEMS) allows the assessment of
the number of pills missed during a period as well as adherence to a dosing
schedule.
 The system electronically monitors when the pill bottle is opened, and the
researcher can periodically download the information to a computer.
 The availability and cost of this system could limit the feasibility of its use.

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5. Pharmacy Records and Prescription Claims
 This method can be used primarily for medications that are taken for chronic
illness.
 The records provide only an indirect measure of drugs consumed.
 Patterns of over and under consumption for periods less than that between
refills cannot be assessed.

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6. Patient Interviews
 Studies have consistently shown that third-party assessments of medication
adherence by healthcare providers tend to over estimate patient’s adherence.
 Interviewing patients to assess their knowledge of the medications they have
been prescribed and the dosing schedule provide little information as to
whether the patient is adherent with the actual dosing schedule.
 Subjective assessments by interviewers can bias adherence estimates.
 This method is rarely used in medical research to assess adherence.

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7. Patients Estimates of Adherence
 Direct questioning of patients to assess adherence can be an effective
method.
 However, patients who claim adherence may be underreporting their non
adherence to avoid caregiver disapproval.
 Other methods may need to be employed to detect these patient.

31. DIAGNOSIS AND THERAPY SURVEYS
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 Survey data related to prescription of clinicians and the rates of disease
encountered in practice are also useful in Pharmacoepidemiological studies to
measure the outcome.
 In many countries established organization and agencies are collecting such
information and make it available in their databases.
 In India researcher have to depend on local data collected by themselves as no
computer system is in existence to survey the prescriptions or registering the
details for the use of studies and research.

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REFERENCES
1. https://www.who.int/tools/atc-ddd-toolkit (WHO)
2. Pharmdguru.com
3. Pharmacoepidemiology and Pharmacoeconomics: Concepts and practice by K.G
Ravikumar, Page no :113- 117.
4. https://gsravani.gitlab.io/pharmdnotes/monetary%20units.html

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