Why must the nurse instruct a patient receiving metformin (Glucophage XL) to avoid crushing or chewing the medication?

A. The patient may choke: This is not the primary concern for extended-release medications like metformin (Glucophage XL). While choking is a risk with any pill, it's not specific to the need for avoiding crushing or chewing extended-release formulations.
B. It would cause blood glucose levels to rise too rapidly:  Crushing or chewing the medication would not cause blood glucose levels to rise rapidly. Instead, it could lead to a more rapid release and absorption of the drug, which might lower blood glucose too quickly, potentially leading to hypoglycemia.
C. Irritation of the oral mucosa may occur:  While irritation of the oral mucosa could be a concern with some medications, it is not the primary reason for avoiding the crushing or chewing of extended-release formulations like Glucophage XL.
 D. The effect of the medication may be changed:  Crushing or chewing an extended-release tablet disrupts its formulation. Glucophage XL is designed to release metformin slowly over time. If the tablet is crushed or chewed, it can result in the entire dose being released at once, which can alter the intended pharmacokinetics and pharmacodynamics of the drug. This could lead to a higher risk of side effects and a loss of the extended-release benefit, ultimately changing the medication's effect and possibly leading to issues like hypoglycemia or gastrointestinal side effects.