It is common for patients to stop _ medicine as soon as they start feeling better.

The correct option is 'taking' because 'taking medicine' is the standard English collocation for the consumption of medication. Medical literature and health guidelines consistently use this phrase when discussing patient adherence. For instance, patients are often warned not to suddenly 'stop taking' their medicine even when they begin to feel better [1]. While 'swallowing' refers to the physical act of moving a pill down the throat [2], 'taking' encompasses the entire regimen of administration. Research indicates that a significant percentage of patients intentionally stop taking medications, such as antidepressants, as soon as they experience symptomatic relief. This behavior is a major concern in public health because abrupt discontinuation can lead to withdrawal symptoms or the return of the underlying condition. Therefore, 'taking' is the most appropriate and contextually accurate verb for this sentence.

Sources

1. [1] https://www.fda.gov/drugs/drug-safety-and-availability/fda-identifies-harm-reported-sudden-discontinuation-opioid-pain-medicines-and-requires-label-changes
2. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC7810703/