system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why do we have to take water with some medicines, is it just easier to swallow?
gpt
It's not just the easier-to-swallow thing.

Some medications (nonsteroidal anti-inflammatory agents (NSAIDs) and bisphosphonates, in particular)  can be less effective if taken without water, and if they *do* happen to get stuck, some may irritate the esophagus, and cause ulcers, heartburn and/or chest pain.

Lithium can cause dehydration, so taking it with water is important, and if a medication reaches your kidneys without being diluted, it may cause kidney stones or even damage the kidneys.  Water helps dilute the medication so that too much of it doesn't pass through the kidneys at one time.

In general, unless your doctor of pharmacist recommends otherwise, all medications should be taken with water; if the medication calls for 'plenty of water', you may need more than one glass.