See also How to Use and Precautions sections.Your healthcare professionals (e.g., doctor or pharmacist) may already be aware of any possible drug interactions and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.This drug should not be used with the following medication because a very serious interaction may occur: dofetilide.If you are currently using the medication listed above, tell your doctor or pharmacist before starting quinapril with hydrochlorothiazide.Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: aliskiren, cisapride, drugs affecting the bone marrow (e.g., azathioprine), drugs that can increase dizziness (e.g., phenobarbital, narcotic pain relievers such as codeine), diazoxide, lithium, probenecid, drugs that may increase the level of potassium in the blood (such as ARBs including losartan/valsartan, birth control pills containing drospirenone), other "water pills" (diuretics such as amiloride, furosemide, triamterene), gold injections.This product contains magnesium which can interfere with the absorption of some medications. For example, if you are taking a tetracycline antibiotic, take it at least 2 hours apart from quinapril/hydrochlorothiazide. If you are taking a quinolone antibiotic (e.g., ciprofloxacin, levofloxacin) or a bisphosphonate (e.g., risedronate), consult your pharmacist for the proper times to take those medications apart from quinapril/hydrochlorothiazide. This is not a complete list.A very serious reaction may occur if you are getting injections for bee/wasp sting allergy (desensitization) and are also taking quinapril with hydrochlorothiazide. Make sure all your doctors know which medicines you are using.Check the labels on all your medicines (e.g., cough-and-cold products, diet aids, nonsteroidal anti-inflammatory drugs-NSAIDs for pain/fever reduction) because they may contain ingredients that could increase your blood pressure (e.g., pseudoephedrine, phenylephrine) or reduce the effect of this medication (e.g., ibuprofen, naproxen). Ask your pharmacist about the safe use of those products.This product can affect the results of certain lab tests. Make sure laboratory personnel and all your doctors know you use this drug.This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.