Data Visualization and Data Summary - Text Mining Techniques for Healthcare Provider Quality Determination - page 61

Fosamax® is generally used once weekly, so there are four tablets prescribed for a month with 12
prescriptions a year if the patient is taking the medication properly. Once the data have been prepro-
cessed, we can examine the relationship of medication to patient prescriptions and to the quantity of
doses in the prescription. Table 5 shows the number of pills given for a prescription dose of Actonel®.
Almost 80% of the patients receive a 30-day supply with 9.5% receiving less than a 30-day supply
and 4% receiving a 90-day supply. Because of the standard dispensing practices, the 30-day and 90-day
prescriptions should be the norm in the dataset. If we limit our analysis to these patients, omitting the
remaining as perhaps in error, we can examine whether these patients are complying by looking at the
total number of prescriptions in a year. For Boniva®, which is taken once a month, 22 patients receive 1
dose, 14 receive 2 doses, and 2 receive 3 doses in the prescription. Similarly, Table 6 shows the number
of doses for the drug, Fosamax®.
The values of 30, 69, and 300 seem excessive. However, while Fosamax® is most commonly taken
once a week, there is a daily version of 10 mg, and the patients beyond 12 doses are probably taking
that version. Otherwise, the most common prescriptions are for a 30-day supply (4 pills) and a 90-day
supply (12 pills). Prescriptions for other medications are much more scattered, making it more difficult
to examine patient compliance.
Given the above information, we next want to examine the total number of doses by patient. One of
the difficulties in this dataset is that the RXSTRENG variable is character rather than numeric. The reason
for this is because liquid doses are given as a ratio of drug to medium, where the medium is usually some
type of saline or dextrose solution. Since we are working with a medication that is almost always given
by mouth, we want to remove all non-tablet formulations, and convert the column to numeric. Then we
can consider the sum of the quantities, where the sum is taken over all of the prescriptions for any one
patient. We can also compute the average number of doses per prescription, and the number of prescrip-
tions in the year to examine the level of patient compliance. Another consideration is that Fosamax®
is generally taken once a week, but the 10 mg dose is taken daily. Therefore, when we consider patient
compliance, we will need to separate Fosamax® by dose. We use the following code to investigate the
total medication prescribed over the one year period of 2005:

Table 5. Number of pills per prescription for Actonel®

Number of Pills Frequency Percent of Prescriptions

1 26 2.61

2 18 1.81

3 51 5.12

4 794 79.72

5 9 0.90

8 6 0.60

9 5 0.50

12 39 3.92

20 2 0.20

24 1 0.10

30 35 3.51

90 10 1.00