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This suggests that there’s a causal relationship, but a registry study can’t answer that question, it is possible that those who received PDE5 inhibitors were healthier than those on alprostadil and therefore had a lower risk. To ascertain whether it is the drug that reduces the risk, we would need to randomly assign patients to two groups, one that takes PDE5 and one that doesn’t. The results we have now give us very good reason to embark on such a study.