What effect may patients experience upon standing after taking Hydrochlorothiazide and Triamterene?

Patients taking Hydrochlorothiazide and Triamterene may experience lightheadedness upon standing due to orthostatic hypotension, which is a common side effect of medications that act as diuretics. Hydrochlorothiazide is a thiazide diuretic that helps to reduce blood pressure by promoting the excretion of sodium and water through the kidneys, while Triamterene is a potassium-sparing diuretic that helps maintain potassium levels. The use of these diuretics can lead to a reduction in blood volume, which may affect blood pressure regulation when transitioning from a sitting or lying position to standing.

This decrease in blood pressure can result in insufficient blood flow to the brain, leading to lightheadedness or dizziness. It is essential for patients to be aware of this potential effect, especially when starting treatment or adjusting dosages. The other options, such as increased alertness, constipation, and fatigue, are not commonly associated with this combination of medications, making lightheadedness the most likely effect experienced by patients upon standing.