Which of the following is a common anticholinergic side effect?

The common anticholinergic side effect among the options provided is blurred vision. Anticholinergic medications work by blocking the action of the neurotransmitter acetylcholine. This can lead to a range of side effects, particularly relating to the eyes. When acetylcholine action is inhibited, it can cause dilation of the pupils (mydriasis), which may lead to blurred vision and difficulty focusing, especially in varying light conditions. This is a well-known and recognized effect when using anticholinergic agents, making blurred vision a classic symptom associated with their use.

Other potential side effects of anticholinergics can include dry mouth, constipation, and urinary retention, but these options do not correlate with the choices. While nausea, insomnia, and palpitations can occur with various medications or conditions, they are not characteristically recognized as anticholinergic side effects. Thus, blurred vision stands out as a primary consequence of anticholinergic activity in the body.