May cause a variety of side effects, ranging from mild to serious. Common side effects include dizziness, especially when standing up quickly, and fatigue. Some people may experience headaches, nausea, or increased urination due to the diuretic effect of hydrochlorothiazide. Quinapril can also cause a persistent dry cough, a side effect often associated with ACE inhibitors. More serious side effects include angioedema, which is swelling of the face, lips, tongue, or throat, and can be life-threatening if it impairs breathing. Other potential serious side effects include kidney problems, such as changes in urination or swelling, and electrolyte imbalances, including low potassium, sodium, or magnesium levels, which can affect heart rhythm and cause muscle weakness or cramps. Hyperkalemia (high potassium levels) is another concern, which can lead to dangerous heart problems. Some people may also experience skin reactions like rashes, or allergic reactions such as itching or difficulty breathing. If any severe reactions occur, or if you experience symptoms like swelling, trouble breathing, or chest pain, seek immediate medical attention. Regular monitoring of kidney function and electrolytes is often necessary to prevent these side effects.

Comes with several important warnings that should be considered before use. First, kidney function should be monitored regularly, as this medication can affect kidney function, particularly in individuals with pre-existing kidney disease. Dehydration or a low blood volume (hypovolemia) can also increase the risk of side effects, such as low blood pressure (hypotension) and kidney issues. Patients who are pregnant should avoid this medication, as quinapril can harm the fetus, particularly in the second and third trimesters. It is contraindicated during pregnancy, and a healthcare provider should be consulted for alternative treatments. Electrolyte imbalances, such as low potassium or sodium levels, are also a concern due to the diuretic (HCTZ) component, so regular monitoring is recommended. This medication should be used with caution in patients who have a history of heart disease or liver disease.

An important warning is the risk of angioedema, a potentially life-threatening allergic reaction that causes swelling of the face, lips, tongue, or throat, which can impair breathing. If you experience any signs of angioedema, such as swelling or difficulty breathing, seek emergency medical attention immediately. Alcohol and salt substitutes containing potassium should be used cautiously while taking Quinapril/HCTZ, as they can increase the risk of hyperkalemia (high potassium levels), which can cause dangerous heart rhythms. It is essential to follow your healthcare provider's instructions carefully, avoid skipping doses, and contact them if you experience any unusual symptoms.

Can be dangerous and requires immediate medical attention. Symptoms of an overdose may include severe low blood pressure (hypotension), which can cause dizziness, fainting, or confusion. Since quinapril lowers blood pressure and hydrochlorothiazide increases urination, an overdose can lead to significant dehydration, electrolyte imbalances, and kidney damage.