Hello. Thank you for asking on HCM. I hope I can help with your concern. To get to the exact answer you asked I would need some more information. Have you ever experienced epigastric or chest pain? Was this dark color stool a one-time episode or it happened any time before or during this period? I would like to point out that dark colored stool can easily happen to anybody who consumes certain food, which darkens the stool, such as food with iron in its content, red wine, beet root etc. It is also true that aspirin expresses its effect by strongly inhibiting prostaglandin formation, a very important factor which, in stomach, acts by inhibiting acid formation. After a certain amount of time that aspirin is used, it can predispose the ulcer formation, by inhibiting prostaglandins (acid formation inhibitors and equalizers) - more acid is produced - the innermost lining of the stomach, mucosa, faces more acid - mucosa is eroded - ulcer can be formed. Actually, this is also an effect of all NSAIDs. Being this the case or not, in my experience, I always accompany aspirin and NSAIDs with a gastric protector such as hystamine H2-receptor inhibitors (ranitidine) or protein pump inhibitors (omeprazole, esomeprazole). First thing I would recommend is that you should do a complete blood count, to see if this dark color is from any blood leakage or it is just alimentary in origin. As for the high blood pressure, I would need more information about the figures of daily blood pressure, to further tell you if losartan is sufficient to treat it. Anyway, After you have provided the blood pressure figures, feel free to ask me again, or consult your treating cardiologist. I hope I was helpful. Best regards.