Phenolphthalein tablets are laxatives, mainly used for the treatment of habitual and stubborn constipation. Phenolphthalein tablets mainly act on the colon and slowly decompose under the action of alkaline intestinal fluid in the small intestine after oral administration to form soluble sodium salts, thus stimulating the nerve plexus in the intestinal wall and acting directly on intestinal smooth muscle to increase intestinal peristalsis, while at the same time inhibiting the absorption of water in the intestine and allowing water and electrolytes to accumulate in the colon, producing a slow diarrheal effect. Phenolphthalein tablets should be contraindicated in patients with appendicitis, rectal bleeding without a clear diagnosis, congestive heart failure, hypertension, fecal mass obstruction, and intestinal obstruction. Phenolphthalein tablets may change the color of urine to magenta or orange, and the excretion of phenolphthalein is accelerated. Long-term use of phenolphthalein may cause an increase in blood sugar and a decrease in blood potassium, so it is important to pay attention to these abnormalities when using the drug.