Well, if you're going to compare the two, skin rash is less adverse than a blocked artery which is more adverse and more important for the patient well being. Your example is perfect for my side of the story. Here you have both adverse effects of the drug, one important(blocked artery) and the other prevalent(skin rash). The article mentioned the more important side effect(blocked artery) and did not mention the more prevalent side effect(skin rash). So, the article is construed to be right too.