General Problem
Section content first added by: Sandra Minjoe
Often medications collected during a study include those taken prior to initial study drug dosing, those taken while on study drug, and those take after completion of study drug. It can be difficult to determine whether to count a medication as a prior med, a con med, both, or neither.
Prior Meds
Section content first added by: Sandra Minjoe
Prior meds can be defined as those medications taken prior to the initial dose of study drug. Assuming complete dates (and times), this is a simple comparison: if date(time) of medication start is less than date(time) of first dose of study drug, then it is a Prior Med. Otherwise it is not.
Con Meds
Section content first added by: Sandra Minjoe
Con meds can be defined as those medications taken while on study drug but not before the initial dose of study drug. Here a couple of comparisons are needed, again assuming complete dates (and times). First, any medication with a start date(time) less than date(time) of first dose of study drug is not a Con Med. Second, any medication with a start date(time) greater than date(time) of last dose of study drug + some window (window varies, depending on study drug) is also not a Con Med. All remaining medications are thus Con Meds.
Partial Dates (Times)
Section content first added by: Sandra Minjoe
When incomplete dates and times are provided, imputation may be necessary.
Repetitions
Section content first added by: Sandra Minjoe
When a medication is taken repeatedly, multiple records for the same medication with different start dates(times) might cause it to be counted as both a prior med and a con med. A decision must be made whether to group all meds of the same name (or map to the same terminology using a coding system) under a single start date or to treat them as independent records.