Figure 1.

The drug exposure preparation algorithm. qty = total quantity entered by GP for the prescribed product; ndd = derived numeric daily dose; numdays = number of treatment days; dose_duration = derived duration of prescription. The highlighted pathway is the “primary preparation pathway” we defined in the second phase of each analysis; this pathway was used to generate one dataset, then further datasets were generated by varying a single assumption with respect to this primary pathway. All options that produce a missing value stay coded as missing unless otherwise stated. *For options 6d: If only one stop available, use it; if 2 available and equal, use that date; if 2 available and unequal (but within x days), use mean; if 3 available and unequal, use mean of closest 2 if within x days. **Records with missing stop dates after step 7 are dropped