@Dymshyts - Actually I tried to follow the order given here. But it still threw error for constraints.
I started with drug_strength table as shown in the code. But it expects the concepts to be already present in concept table. Hence it resulted in foreign key constraint violation error.
If we look at the order in the script that you shared,it shows that concept table is loaded after drug strength.
But unfortunately it still throws error as shown below.
ERROR: insert or update on table "drug_strength" violates foreign key constraint
"fpk_drug_strength_concept_1"
DETAIL: Key (drug_concept_id)=(37594088) is not present in table "concept".
Am I missing anything here? can you correct me if I am making any mistakes?