Final answer:
Osmotic laxatives work by drawing water into the intestines through osmosis, softening stools and stimulating bowel movements. Mannitol and indigestible sugars like lactulose are common osmotic laxatives. In diabetes mellitus, excessive glucose can act as an osmotic diuretic, leading to increased urine production.
Step-by-step explanation:
How Osmotic Laxatives Work
Osmotic laxatives function by increasing the amount of water in the bowels, which in turn softens stools and stimulates bowel movements. They work by drawing water into the intestines through osmosis, a process where water moves across a membrane from an area of lower solute concentration to one of higher solute concentration. When osmotic laxatives like mannitol or sugars that cannot be digested, such as lactulose, are consumed, they remain in the bowel and pull water into the fecal mass. This water accumulation not only softens the stool but also increases its volume, which stimulates the bowel to pass the stool out.
For individuals with diabetes mellitus, high levels of glucose in the blood can lead to glucose being excreted in the urine. When this happens, the glucose acts as an osmotic diuretic, drawing water into the urine and producing a diuretic effect. This is why classic symptoms associated with poorly controlled diabetes include polyuria, polydipsia, and polyphagia—symptoms historically identified before the modern methods of measuring blood and urine glucose levels..