Which symptom may indicate an adverse reaction in a patient taking carvedilol?

Dizziness after exercising can signal an adverse reaction in a patient taking carvedilol, which is a non-selective beta-blocker. Carvedilol works by blocking beta-adrenergic receptors, leading to effects such as decreased heart rate and reduced blood pressure. When a patient engages in physical activity, the demand for oxygen in the body increases, and if carvedilol is effectively lowering blood pressure, the patient may experience dizziness due to insufficient blood flow to the brain during exercise. This symptom can indicate that the medication is overly potent for that individual or that their body is not adequately compensating for the increased physical demand, suggesting a need for closer monitoring of the patient's response to the medication.

Other symptoms like increased heart rate, nausea before meals, or frequent urination are typically not directly associated with carvedilol's adverse effects. Increased heart rate would be contrary to the expectations with beta-blockers, and nausea or frequent urination are not common indicators of carvedilol's side effects, making dizziness after exercising a notable warning sign.