• Potassium supplements. Use increases the risk of hyperkalemia (too much potassium in the body).

  • Diuretics (some types). Medications that stimulate the kidneys to produce more urine, flushing excess fluids and minerals (e.g., sodium) from the body. Most diuretics cause the body to lose potassium, as well as sodium and fluids. One type – potassium-sparing diuretics – actually preserves potassium while flushing other minerals from the body. Because of this, using potassium-sparing diuretics in conjunction with ACE inhibitors may increase the risk of hyperkalemia. In patients taking both types of medications, risk of hyperkalemia increases with age and the dosage of diuretic prescribed (greater that 25 milligrams). People with kidney disease or diabetes are also more likely to develop hyperkalemia when taking these medications in combination.

  • Salt substitutes. Many of them contain potassium chloride, which increases the risk of hyperkalemia.

  • Low-salt milk. Use increases the risk of hyperkalemia.

  • Alcohol. Drinking alcoholic beverages can produce a drop in blood pressure. Patients taking ACE inhibitors should consult their physician before drinking alcohol.

  • Nonsteroidal anti-inflammatory drugs (NSAIDs). These can decrease the effectiveness of the ACE inhibitors, worsen high blood pressure or increase the risk of kidney problems. Patients should consult with their physician before using them. A possible exception to this is aspirin. While aspirin is technically a type of NSAID, research has suggested that aspirin use – especially the low doses associated with daily aspirin therapy – may be safe for heart patients. Patients should discuss the potential benefits and risks with their physicians.

  • COX-2 inhibitors. These medications decrease the blood pressure-lowering effects of ACE inhibitors. However, they may pose less of a risk for future kidney problems than some NSAIDs. Patients taking ACE inhibitors should consult with their physicians before using these medications.

  • Grapefruit juice. Grapefruit juice interferes with the liver’s ability to rid the body of some substances. This could lead to a build up of ACE inhibitors to toxic levels in the body. Although the buildup is less likely if the juice is ingested four or more hours prior to the medicine, patients taking ACE inhibitors are advised to refrain from drinking grapefruit juice.

  • Over-the-counter (OTC) medications that increase blood pressure. Patients taking ACE inhibitors for high blood pressure should avoid OTC products that may increase blood pressure, such as those used for appetite control, asthma, flu, colds, cough, sinus problems or hay fever.

  • Other substances that may adversely react with ACE inhibitors include narcotics (prescription painkillers), tobacco, and marijuana or other illegal drugs.