Antihypertensives are medications used primarily to treat high blood pressure (hypertension). They are often prescribed for diabetic patients. About 60 percent of people with diabetes also have high blood pressure.

High blood pressure is a major contributor to the development of the kidney disease diabetic nephropathy, atherosclerosis (“hardening of the arteries”), heart conditions, stroke and eye diseases such as diabetic retinopathy and glaucoma. Because patients with diabetes have a higher risk of these disorders, it is especially important to diagnose and treat even mild hypertension.

People with diabetes whose blood pressure is 130/80 millimeters of mercury (mmHg) or greater are considered to have high blood pressure and should be treated accordingly, according to the National Institutes of Health and the American Diabetes Association (in nondiabetics, this reading would be considered prehypertensive). In addition, some diabetic patients with normal blood pressure are prescribed antihypertensives to treat or prevent complications such as kidney disease.

Although some patients do not need to take medication to control their high blood pressure, anyone who is prescribed medication needs to take it exactly as prescribed to avoid the serious medical problems associated with the condition.

People taking antihypertensives are also encouraged to make healthy lifestyle changes, such as quitting smoking, losing weight and getting regular exercise. Furthermore, they are encouraged to speak with their physician before taking any prescription medications, such as opioids, or over-the-counter medications, such as diet pills.

People with high blood pressure are urged to be patient as the type and level of their medication are adjusted for optimal results. This is especially important because the vast majority of patients have no symptoms, making hypertension the “silent killer.” There are a wide variety of antihypertensives and combinations of different medications that are available, and it may take time before the ideal treatment has been found and finely tuned to the patient’s needs.

Other uses of antihypertensives include treatment of hyperthyroidism, glaucoma, chest pain, prostate enlargement, headaches and diabetes insipidus.

Antihypertensives are medications used to treat high blood pressure (hypertension). Blood pressure is a measure of the force of the blood pushing against the walls of the arteries.

As many as 60 percent of people with diabetes have high blood pressure, according to the American Diabetes Association (ADA). Hypertension refers to an elevation of the blood force against the arterial walls. It is an indication that the heart and the blood vessels are being overworked. 

High blood pressure contributes to disorders including:

• Cardiovascular problems such as atherosclerosis (“hardening of the arteries”), diabetic angiopathy, heart conditions and stroke
  
  
• Kidney disease (diabetic nephropathy)
  
  
• Eye diseases such as diabetic retinopathy and glaucoma

Even mild cases of high blood pressure should be treated in people with diabetes. The ADA and the National Heart, Lung and Blood Institute have recommended that patients who have diabetes or chronic kidney disease maintain blood pressure of less than 130/80 mmHg (in nondiabetics, this reading would be considered “prehypertensive”).

Antihypertensives lower blood pressure by several mechanisms including:

• Opening and widening the blood vessels
• Preventing the blood vessels from closing and tightening
• Reducing the workload of the heart

These medications come in many varieties, and some may be more appropriate for people with diabetes than others. Patients diagnosed with hypertension frequently need more than one medication to keep the condition under control. Most patients will need to remain on antihypertensives permanently.

It should be noted that some medications used primarily to treat high blood pressure may also be prescribed for other disorders that do not necessarily involve hypertension. These conditions include heart failure, irregular heartbeat, chest pain, coronary spasms, esophageal spasms, hyperthyroidism, kidney disease, prostate enlargement, headaches and diabetes insipidus.

Antihypertensive medications are available in many varieties. Some may be more appropriate than others for treating people with diabetes. Antihypertensive medications include:

• Vasodilators. Medications that expand or widen blood vessels, reducing blood pressure against the walls of the vessels. This allows blood to flow more freely and the heart to pump more efficiently. Vasodilators include:
  
  
• • ACE inhibitors (angiotensin-converting enzyme inhibitors). Block the production of an enzyme (angiotensin II) that causes blood vessels to tighten. Preventing this constriction allows more blood to flow into the heart and lowers blood pressure.
    
    
  • Angiotensin-II receptor blockers (ARBs). Produce the same effect as ACE inhibitors but by a different mechanism. Instead of preventing the production of angiotensin II, they inhibit the action of this substance by blocking it from entering angiotensin II receptors in the body. These drugs are also frequently prescribed for diabetes patients, especially those who have or are at risk for kidney disease (diabetic nephropathy). Some research indicates that ACE inhibitors and ARBs may reduce the risk of developing type 2 diabetes.
    
    
  • Calcium channel blockers (CCBs). Reduce the workload of the heart by blocking calcium ions from signaling the blood vessels to constrict or tighten. They are commonly prescribed for those with diabetes and are particularly effective when used in combination with ACE inhibitors or angiotensin II receptor blockers. They may be prescribed for conditions including angina, coronary artery disease, coronary spasms, arrhythmias and a type of stroke called subarachnoid hemorrhage.  A recently approved drug combines a CCB with a cholesterol drug to treat two common risk factors for heart disease and diabetes.
    
    
  • Central adrenergic inhibitors. Act directly on the brain to prevent it from signaling the central nervous system to increase heart rate or narrow blood vessels.
    
    
  • Renin inhibitors. Help blood vessels relax and widen by reducing the effect of renin, an enzyme made in the kidneys. The U.S. Food and Drug Administration approved the first renin inhibitor in 2007.
    
    
• Alpha blockers. Medications that reduce the workload of the heart by blocking certain chemicals from binding with alpha receptors in the heart, which relaxes the smooth muscle in the walls of blood vessels. Alpha blockers are often prescribed to treat prostate enlargement (benign prostatic hyperplasia).
  
  
• Beta blockers. Reduce the workload of the heart by blocking some effects of the sympathetic nervous system, which may release certain chemicals that bind with beta receptors in the heart. Binding could trigger a rapid heartbeat. Beta blockers may be the first-line treatment for people with diabetes and heart conditions, such as heart failure, angina, heart attack, arrhythmia or palpitations. They can also treat glaucoma. However, they are often not chosen as first-line treatment for people with diabetes alone, as they can mask symptoms of hypoglycemia in some patients. In addition, several studies have shown that beta blockers can cause hyperglycemia and may even be a risk factor for secondary diabetes.

Beta blockers may be prescribed as thyroid medications to treat Graves’ disease and other forms of hyperthyroidism. Beta blockers and other antihypertensives may be prescribed as headache medications to prevent migraines or cluster headaches.

• Diuretics. Promote the formation of urine in the kidneys, causing the body to flush out fluids and minerals including sodium. The reduction in fluid volume and sodium levels causes blood vessels to widen, increasing blood flow and reducing the pressure of blood against the vessels. Of the four types of diuretics (sometimes called water pills), the three used in the treatment of hypertension are loop, potassium-sparing and thiazide. However, as with beta blockers, some research has indicated that diuretics can raise glucose (blood sugar) and possibly lead to secondary diabetes. Diuretics can also be prescribed for conditions including heart failure, glaucoma and the nephrogenic form of diabetes insipidus.

Some antihypertensive drugs have shown other benefits for diabetic individuals. High blood pressure increases the odds of developing kidney disease in people with diabetes. ACE inhibitors and angiotensin II receptor blockers have been shown to protect the kidneys of those with diabetes and can either slow or prevent kidney damage. These drugs are sometimes prescribed to protect the kidneys in diabetic patients who do not have high blood pressure. The U.S. government’s ALLHAT project (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) found diuretics especially effective for black Americans, including reducing the risk of stroke.

Physicians choose which antihypertensive to prescribe based on each patient’s medical history and symptoms and conditions. Considerations include kidney function, cardiovascular health, eye health, glucose control and tendency to have hypoglycemia unawareness.

If the use of a single antihypertensive does not lower blood pressure sufficiently, then physicians may prescribe two or more types of antihypertensives to work in combination. Combination therapies are usually not first-line treatments but offer a valuable alternative when traditional therapies are not effective. They allow for lower, better-tolerated doses of each antihypertensive.

Some combinations are available in single fixed-dose pills so that although patients are taking more than one medication, they are taking only one pill. The most common combination therapies include:

• ACE inhibitors and thiazide diuretics
• Angiotensin II receptor blockers, thiazide diuretics and potassium-sparing diuretics
• Beta blockers and thiazide diuretics
• Thiazide diuretics and potassium-sparing diuretics
• Calcium channel blockers and ACE inhibitors
• Renin inhibitors and diuretics

Whether or not medication is required to control hypertension, patients will be advised to make lifestyle modifications (healthy diet, weight loss, exercise, quitting smoking) to help control their condition.

Possible side effects when taking antihypertensives include:

• Allergic reaction
  
  
• Hypotension (low blood pressure)
  
  
• Arrhythmia (abnormal heart rhythm)
  
  
• Palpitations (pounding or galloping heartbeat)
  
  
• Dizziness, lightheadedness or fainting (syncope)
  
  
• Headache
  
  
• Edema (swelling) in the legs
  
  
• Increased sensitivity to sunlight (photosensitivity), causing severe sunburn or rash
  
  
• Drowsiness, weakness, tiredness or fatigue
  
  
• Unusual bleeding
  
  
• Back or joint pain
  
  
• Abdominal discomfort, nausea, diarrhea or constipation
  
  
• Unusual skin appearance (rash, blue tinge, or a yellow tinge called jaundice)
  
  
• Shallow, dry cough (especially with ACE inhibitors)
  
  
• Impotence
  
  
• Depression

A recently discovered potential complication of alpha blockers is an eye condition called intraoperative floppy iris syndrome (IFIS), which can interfere with cataract surgery. This complication is of particular concern because diabetes and obesity have been found to increase men’s risk of prostate enlargement (benign prostatic hyperplasia), for which alpha blockers are often prescribed, and diabetes increases the risk of cataracts. Patients who have ever taken alpha blockers should inform their ophthalmologist before cataract surgery because different surgical techniques may be used to ensure a successful outcome.

Patients should consult their physician before taking any other medication (either prescription or over-the-counter), nutritional supplements or herbal remedies. Substances that can intensify the effects of antihypertensives and possibly lead to hypotension (low blood pressure) include:

• Other antihypertensives (unless prescribed as part of a combination therapy).
  
  
• Nitrates (medications that relax the arterial walls, causing a drop in blood pressure).
  
  
• Alcohol.
  
  
• Grapefruit juice. Grapefruit juice interferes with the liver’s ability to rid the body of some substances. This could lead to a buildup of antihypertensives to toxic levels in the body. Though the buildup is less likely if the juice is ingested four or more hours before taking the medicine, patients taking antihypertensives are advised to refrain from drinking grapefruit juice. There is no indication that eating grapefruit (as opposed to drinking juice) presents any danger to patients.
  
  
• Pomegranate juice. This fruit juice may reduce blood pressure. Patients taking antihypertensives are advised to ask their physician whether they can safely drink pomegranate juice and whether doing so can affect their dosage.
  
  
• Certain other foods. Some research suggests that foods including dark chocolate and soy protein may lower blood pressure. 

The following substances may counteract the effects of some antihypertensives and increase blood pressure.

• Opioids (prescription narcotic painkillers).
  
  
• Nicotine (present in tobacco products such as cigarettes).
  
  
• Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, naproxen and COX-2 inhibitors. The U.S. Food and Drug Administration (FDA) warned in 2005 that COX-2 inhibitors may cause an increase in serious gastrointestinal bleeding and cardiovascular events such as heart attack and stroke. Some of the medications have been removed from the market. Because of these issues, the side effects caused by NSAIDs and their many interactions with other drugs and substances, patients are encouraged to discuss NSAIDs with their physician before using the drugs.

In addition, some over-the-counter medications may adversely react with antihypertensives, including diet pills and medications for asthma, colds, flu, cough, sinus problems or hay fever. People should also be careful of using eye drops for bloodshot eyes.

When first taking antihypertensives, patients are advised to avoid driving or operating other heavy machinery until they know how the medication will affect them. Most people on medication to treat high blood pressure will be taking it for the rest of their lives, provided no serious side effects occur.

Patients should remember that antihypertensives control high blood pressure but do not cure it. They should also know that over time, some antihypertensive medication may become less effective in treating their condition, and they may have to switch to another dosage or drug.

Patients are encouraged to continue to see their physician for regular follow-up to ensure that their blood pressure is under control, even if it appears that symptoms have been relieved. Controlling glucose (blood sugar) can also help people with diabetes lower their blood pressure. In addition to taking their medications as prescribed, patients may be advised to make lifestyle modifications, especially concerning a nutritious diet, exercise, weight loss, quitting smoking and stress management.

Patients should inform their physician if they become sick, especially with severe vomiting or diarrhea. These conditions could cause the body to lose too much water and potassium, leading to dehydration and low blood pressure (hypotension).

A person's exposure to heat may intensify the adverse effects of antihypertensives. Patients should drink enough liquids during exercise or in hot weather and adhere to their physician’s instructions regarding exercise, activity levels and diet.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about antihypertensives:

1. Am I being prescribed an antihypertensive for high blood pressure or for another condition?
   
   
2. What is the name of my drug and the dosage?
   
   
3. How and when should I take it?
   
   
4. What should I do if I miss a dose?
   
   
5. Should I avoid grapefruit juice, pomegranate juice, alcohol or other substances?
   
   
6. Do I need to avoid driving when starting this medication?
   
   
7. What side effects might I experience from this medication? Can it affect my blood sugar?
   
   
8. At what point do side effects require me to seek medical attention?
   
   
9. Can this medication improve or worsen my diabetes or risk of diabetic complications such as kidney disease?
   
   
10. Can this drug interact with my other medications?
    
    
11. Is there a danger I will experience low blood pressure, especially if my condition being treated does not involve high blood pressure?
    
    
12. How long should I wait and what should I do if the medication does not seem to improve the condition?
    
    
13. Should I improve diet, exercise or other habits?
    
    
14. What are other possible treatments if this drug does not help me?