The drugDrugByProductID(...) function is used to see if a drug will interact with another drug.  The result of drugDrugByProductID(...) is an array of type String[String] with three specific values:

drugInteraction = drugDrugByProductID( productID_1, productID_2);

drugInteraction["severity"]: Severity of the drug interaction
drugInteraction["description"]: A description of the interaction
drugInteraction["advice"]:  Advice if taken together.

Syntax:
drugDrugByProductID( productID_1, productID_2 )
productID_1.drugDrugByProductID( productID_2 ) 

Parameter	Description
productID_1	ProductID 1 for a drug from the "medName" lookup
productID_2	ProductID 2 for a drug from the "medName" lookup

The drugInteraction["description"] contains two place holders for the actual drug names.  These place holders are called {CS1} and {CS2}.  Use the replace(...) function to insert the correct drug Name.  Example:

description = drugInteraction["description"].replace("{CS1}", drugName1)
                                            .replace("{CS2}", drugName2)