Yes it is recommended. The standard drug being used in the study should be specifically targeted against the disease under investigation. It enables to have a comparative analysis on the effect of your drug with that of the commercially available one. Further, most of the pharmacology journals prefer to have a standard group for publication of your results.
studying variations will always be required for statistical approaches. just take care at the number of cases and controls you'll have to overcome individual variations among groups (3 is a minimum, 5 is good, more is better).