Which of these is a potential side effect of long-term use of bismuth subgallate?

Long-term use of bismuth subgallate can lead to peculiar sensations in the fingers and toes, which may be attributed to the substance's effects on the nervous system. Bismuth compounds, when consumed over extended periods, may cause various neuropathic effects due to their interference with certain bodily functions and the accumulation of bismuth in the body. Such effects can manifest as tingling or numbness in extremities, commonly known as peripheral neuropathy.

While the other options may represent potential side effects of various medications or conditions, they are not well-documented outcomes specifically associated with bismuth subgallate. Increased appetite tends to be related to medications or conditions affecting metabolism, headaches may arise from diverse causes unrelated to this particular drug, and increased heart rate could be linked to numerous factors, including stress and other medications, rather than being a direct side effect of bismuth subgallate.