Which of the following is a common adverse drug reaction to Nifedipine?

Nifedipine, a calcium channel blocker primarily used for the treatment of hypertension and angina, can cause several common adverse effects due to its mechanism of action. Flushing occurs frequently as a result of the vasodilatory effects of Nifedipine. When the drug dilates blood vessels, it can lead to increased blood flow and warmth in the face and skin, which manifests as flushing. This response is particularly common during the initial phases of treatment and can vary in severity among individuals.

On the other hand, insomnia, constipation, and weight gain are less commonly associated with Nifedipine. While some patients might experience insomnia as part of an overall discomfort or anxiety related to their condition, it is not a direct result of the medication. Constipation is not a well-documented adverse effect of Nifedipine, as the drug typically promotes vasodilation without significantly impacting bowel motility. Weight gain is also not a typical side effect associated with Nifedipine and does not occur as a result of the drug's pharmacological action.

In summary, flushing stands out as a common and expected adverse reaction to Nifedipine due to its effects on the vascular system, making it the correct answer.