the world organization developed methodology to calculate drug load that is based on a measur of equipotency know as the defined daily dose. The DDD is the average maintenance dose per day for a drug used for its main indication in adults. The ratio of the prescribed daily dose to the DDD converts the daily dose strength into multiples of the DDD. A ratio of 1 means the dose taken is equal to the DDD,a ratio greater than 1 means the dose taken is larger than the standard dose,and a dose less than 1 means the dose taken is smaller than the standard dose. The drug load is the sum of the PDD/DDD ratio for all drug taken within one medication class. Researchers have used a PDD/DDD ratio of 1.5 as the cutoff of 2.0 for anticonvulsant