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★★☆Single study — solid evidence, such as one good trial or a large observational dataset, but not replicated at the top tier.
If you take an alpha-blocker, sildenafil starts at 25mg
Alpha-blockers relax blood vessels by a route of their own. Add sildenafil and some men cannot hold their blood pressure up on standing.
What the study found
On an alpha-blocker, the sildenafil starting dose drops to 25mg
Alpha-blockers, taken for high blood pressure or an enlarged prostate, relax blood vessels by a route of their own. Add sildenafil and some men cannot hold their pressure up on standing, so the label requires being settled on the alpha-blocker first and starting sildenafil at 25mg.
The caveat · Blood-pressure readings, not falls
The rule is written from blood-pressure measurements, not from counted faints or falls. How much it matters may depend on how long a man has already been on his alpha-blocker, and the review reporting that describes it as suggested rather than settled.