Complex sentence: In doses lower than 800mg daily its constricting effects on the bronchial system and smooth muscle vessels are only 10% to 30% of those observed under Propranolol treatment, but there is experimental evidence that the cardioselective properties diminish at doses of 800mg/day or more.
Split into simpler sentences: In doses lower than 800mg daily its constricting effects on the bronchial system and smooth muscle vessels are only 10% to 30% of those observed under Propranolol treatment. But there is experimental evidence that the cardioselective properties diminish at doses of 800mg/day or more.