An analysis of 47 hospitals found that prescription rates dramatically decreased following the price hikes of Isuprel and Nitropress, a pair of heart drugs owned by Valeant Pharmaceutical Industries.

The study, published in the New England Journal of Medicine, said that Valeant hiked the wholesale acquisition cost of Nitropress by 32% and Isuprel by 68% between 2012 and 2015. At the same time, the number of patients prescribed Nitropress and Isuprel at the surveyed hospitals decreased by 53% and 35%, respectively.

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In 2015, lawmakers demanded that the drugmaker explain why it increased the prices of the two heart drugs. Valeant, which acquired Isuprel and Nitropress from Marathon Pharmaceuticals in early 2015, had reportedly increased their prices by more than 500% and 200%, respectively.  The request sparked numerous federal investigations into Valeant’s pricing practices, and began an example of the oft-criticized practice of repricing of old drugs in the ongoing debate about how pharmaceutical companies should price their drugs.

The study also analyzed two other cardiovascular drugs — nitroglycerin and dobutamine — that had more stable pricing and found that their prescription numbers increased, despite a price hike for nitroglycerin. Brand name version of nitroglycerin include Pfizer’s Nitrostat and Allergan’s Rectiv.

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“These findings refute the claim that price increases do not reduce patients’ access to these medications,” the authors of the study wrote. “Decreasing demand also indicates a correcting market response to increased prices that may be a valuable restraining force to pharmaceutical price increases.”