Your mini guide to various drug use measurements

1. Drug Use Measurements
By Anjali Bodapunti
Pharm D 5th Year
SNVPMV

2. Introduction
 Medication adherence is defined by the WHO as "the degree to which
the person's behavior corresponds with the agreed recommendations
from a health care provider”. It also applies to other situations such
as medical device use, self care, self-directed exercises, or therapy
sessions.
 In any event, clinical judgement is required in establishing outcomes.
Morbidity is 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 (events/100/year).

3. Drug Use Measures:
1. Monetary Units
2. Numbers of prescription
3. Units of drug dispensed
4. Defined Daily doses
5. Prescribed daily doses
6. Medication adherence measurement

4. 1. Monetary Units:
 Drug use is measured in monetary units to qualify the amounts of drug
being taken by a population.
 It can indicate the burden on a society.
 These are convenient and can be converted into a common unit,
allowing for comparison.
 The disadvantage of quantities of drugs actually consumed are not
known and prices may vary, widely.

5. 2. Numbers of prescriptions:
 It has been used in Research due to the availability and ease.
 The disadvantage is, qualities dispensed vary greatly as duration of
treatment.
 Example: Treatment of antibiotics: provides a good estimate of
number of people exposed to the drug and its frequency too.

6. 3. Units of drug dispensed:
 Unit dosages like tablets, vials etc. is easy to obtain and can be used
to compare usage trends within population.
 Disadvantage: No information is available on the quantities actually
taken by the patient, making it difficult to understand the actual
number of patients exposed to the drug.

7. 4. Defined daily doses:
 It is the estimated average maintenance dose/day of a drug when
used in its major indication.
 Normally expressed as DDD/1000 patients/day (OR) DDD/100
beds/day
 Advantages: Usefulness for working with readily available drug
statistics, allows comparisons between drugs of same class, describing
and comparing patterns of Drug use and provides denominator data
for estimation of ADR rates.
 Disadvantage: doses varying widely like in antibiotics (OR) when one
drug has more than 1 major indication as causes problems.

8. 5. Prescribed daily doses:
 It is the average daily dose of a drug that has actually been
prescribed.
 Calculated from representative sample of prescriptions.
 Disadvantage: Does not indicate no. of population exposed to drug.
 However, it provides estimate of no. of person-days of exposure.

9. 6. Medication Adherence
Measurements:
1. Biological Assays: Measures the concentration of a drug, its
metabolites or tracer compounds in the blood or urine of a patient.
 Drug/food interactions, physiological differences, dosing schedules
and t1/2 of the drugs might influence the results.
 Biological tracers might be of an ethical concern issue.
 All these methods have high costs for assays limiting the feasibility of
these techniques.

10. 2. Pill Counts: Counting the no. of pills remaining in a patient’s supply
and calculating the no. of pills that the patient has taken since the filling
of prescription is the easiest way to calculate patient drug adherence.
 Patterns of non-adherence are often difficult to discern with a simple
count of pills on a certain date weeks to months after the prescription
was filled.

11. 3. Weight of Topical Medications: The weight of a topical medication
remaining in the tube given is used to measure adherence.
 This was effective as, when compared with patient log books of daily
medication use, weight estimates were fairly lower than patient log
estimates.
 This is a primary measure tool in clinical trials that involve topical
applications.

12. 4. Electronic Monitoring:
 The Medication Event Monitoring System (MEMS) allows the
assessment of no. of pills missed during a period as well as adherence
to a dosing schedule.
 This electronically monitors when the pill bottle is opened and the
researcher can periodically download the information in a computer.
 The cost and availability of this system limits the feasibility of its use.

13. 5. Pharmacy Records and Prescription Claims:
 Used for medications that are taken for chronic illnesses (HTN).
 They provide an indirect measure of drugs consumed, indirectly.
 Patterns of over and under consumption for periods less than that
between refills cannot be assessed.

14. 6. Patient Interviews:
 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 evidences by interviewers can bias adherence estimates.
 Rarely used in medical research to assess adherence.

15. 7. Patient Estimates of Adherence:
 Direct questioning of patients to assess adherence can be an effective
method.
 Patients might lie leading to under-reporting as to avoid caregiver’s
disapproval. Other methods are to be in use to detect these patients.

16. SCALED QUESTIONNAIRE:
Morisky 4 item scale:

17. Hill-Bone compliance scale to High Blood pressure therapy:

18. THANK YOU.