Which of the following conditions is a common result of parasympathomimetic drug action?

Parasympathomimetic drugs mimic the effects of the parasympathetic nervous system, which is often associated with 'rest and digest' functions. When these drugs are active, they lead to a variety of physiological changes in the body aimed at promoting relaxation and conservation of energy.

Lower blood pressure is a common result of parasympathomimetic drug action because these drugs cause vasodilation and a decrease in heart rate. The parasympathetic nervous system activates the release of acetylcholine, which slows down the heart rate and subsequently can reduce the force of heart contractions. This overall effect can lower systemic vascular resistance and, as a consequence, blood pressure.

In contrast, the other options describe effects typically not associated with the action of parasympathomimetic drugs. Increased heart rate and increased alertness are more associated with the sympathetic nervous system, which prepares the body for 'fight or flight' responses. Similarly, decreased reaction time is more aligned with the calming effects of parasympathetic activity, but it does not represent a direct effect of parasympathomimetic drugs as a whole. Instead, these drugs primarily promote relaxation and are linked with decreased heart rate and lower blood pressure.