We have used the rules.
- If the drug exposure from a procedure code then end_date = start_date
- If the is an indication that the drug received via mail order then end date = start_date + 89 days
- Otherwise the drug is assumed to be a pharmacy fill and end_date = start_date + 29.
You might also try to estimate end date if you have days supply or quantity.
We have also created a table with the drug identifier and average number of days for records that do have an end date and then would use this lookup table to determine the end date for records that did not have an end date or days supply.
Anyway these are some options