  We found  181 distinct DDI being prescribed concomitantly to almost 5 \% of the city population.
<meaning-changed>   We found  181 distinct DDI being prescribed concomitantly to almost 5 \% of the city population.
 This is the first study of DDI we are aware of that follows an entire city longitudinally for 18 months. We found 181 distinct DDI being prescribed concomitantly to almost 5 \% of the city population.