Not all pills can be cut or crushed. Here are the reasons:
Long-acting formula / Sustained-release formula
These medications usually have abbreviations such as XR, ER, CR, etc. next to the drug name.
The outer shell of these long-acting formula/sustained-release formula tablets (or capsules) may look thin and simple to the naked eye, but these outer shells are actually specially designed with technology to slowly release the medications they carry after ingestion. Beginning from the stomach, the outer shell releases a fixed dose of medication every hour as it travels through our digestive system, enabling a stable absorption of the medication within 12 or 24 hours after ingestion. When this outer shell is crushed or cut, the content of the pill will be released all at once within a short period of time. The body may then be exposed to extremely high doses leading to dangerous side effects with potentially lethal consequences. Also, since all the content was released within the first few hours, there will be no more medications available to the body for the remaining dosing interval, depriving the body of any necessary medication effect.
(e.g. blood pressure medicine Nifidipine XL)
Enteric-coated formula
The absorption of most drugs begins in the small intestine, but some drugs can be easily destroyed by gastric acid and hence must be protected by an enteric-coated shell when entering the stomach. Upon arriving in the intestine, an alkaline environment, the enteric-coated shell then dissolves allowing the release of the medication it carries. If the shell of the enteric-coated formula is cut or crushed, the drug will be destroyed by gastric acid in the stomach and will not reach the small intestine. .
(e.g. antidepressant/neuralgia drug Duloxetine)
Another purpose of the enteric-coated formula is to protect the stomach. Some acidic drugs can irritate the inner lining of the stomach wall. If a patient needs to take these drugs regularly, an enteric-coated shell can prevent these drugs from being released in the stomach, reducing the risk of gastric bleeding.
(eg Aspirin, Ibuprofen)
Improve taste
Some medicines have a very strong bitter taste, and sugar-coating/film shells can make them easier to swallow.
(such as the sleeping pill Zopiclone)
However, there are always exceptions, such as diabetes medication Gliclazide MR. Although it is a long-acting formula, its oval tablet has a line in the middle that can be cut into half tablets. So if you think the pill you are taking is too big and making it difficult for you to swallow, ask your pharmacist whether the pill can be cut or crushed.