About antihypertensive drugs
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. When this force is elevated beyond a normal level, a patient will be diagnosed with either pre-hypertension or hypertension.
Nearly one in three adult Americans suffer from hypertension, which often occurs without symptoms and for unknown reasons (called essential hypertension). High blood pressure is a major risk factor for stroke, heart attack and heart failure. It frequently occurs in patients with diabetes and is a major contributor to diabetes-related complications, such as kidney failure and eye disease.
Hypertension is an indication that the heart and the blood vessels are being overworked. Hypertension medications lower blood pressure by opening and widening the blood vessels, preventing the blood vessels from closing and tightening, or reducing the workload of the heart. These medications include:
DiureticsSometimes called “water pills,” these medications promote the formation of urine in the kidneys, causing the body to flush out fluid and minerals such as sodium. The reduction in fluid volume and sodium levels causes blood vessels to open wider, increasing blood flow and reducing the pressure of blood against the vessels. Of the four types of diuretics, the three used in the treatment of hypertension are loop, potassium sparing and thiazide.
Beta blockersMedications that 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.
VasodilatorsMedications 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). Vasodilators block the production of a substance (angiotensin II) that causes blood vessels to tighten. This results in lowering the resistance of the blood vessel to the flow of blood from the heart.
- Angiotensin II receptor blockers (ARBs). Vasodilators that 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.
- Calcium channel blockers. Vasodilators that reduce the workload of the heart by blocking calcium ions from signaling the blood vessels to constrict or tighten.
- Central adrenergic inhibitors. Vasodilators that act directly on the brain to prevent it from signaling the central nervous system to increase heart rate or narrow blood vessels.
The choice of which drug to use first is not settled, especially because the various drugs are roughly equally effective. A number of clinical trials have proven this by comparing the drugs in head-to-head studies among various patient groups. The most well-known antihypertensive trial is the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial, or ALLHAT.
The ALLHAT trials began in 1994 and involved more than 42,000 individuals, making it the largest such trial to date. The study showed that “traditional” diuretics about as effective as newer calcium channel blockers and ACE inhibitors but had the added advantage of reducing the development of heart failure and stroke. The researchers concluded that medication therapy to lower blood pressure should begin with diuretics.
Because of ALLHAT, most physicians will begin antihypertensive therapy with a thiazide diuretic and closely monitor its results. However, it's also important to note that the choice of which antihypertensive to use first depends on each patient's medical history and other factors. For example, black Americans tend to respond better to thiazide diuretics and relatively poorly to ACE inhibitors or beta blockers.
If the use of a single antihypertensive does not lower blood pressure sufficiently, 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 single-drug therapy is not effective. They allow for lower, better-tolerated doses of each antihypertensive. Some combinations are available in single fixed-dose pills, so that while patients are taking more than one medication, they are only taking 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
Whether or not medication is required to control hypertension, patients may be advised to make lifestyle modifications to help control their condition.
- Side effects
Potential side effects
The following side effects are possible when taking antihypertensives:
- Allergic reaction
- Low blood pressure (hypotension)
- Arrhythmia (abnormal heart rhythm)
- Palpitations (pounding or galloping heartbeat)
- Dizziness or lightheadedness
- Fainting (syncope)
- Increased sensitivity to sunlight (photosensitivity), causing severe sunburn or rash
- Drowsiness, weakness or fatigue
- Unusual bleeding
- Back or joint pain
- Abdominal discomfort, nausea, diarrhea
- Unusual skin appearance (rash, blue tinge, or a yellow tinge called jaundice)
- Shallow, dry cough (especially with ACE inhibitors)
- Edema (swelling) in the legs
Drug and other interactions
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 low blood pressure (hypotension) include:
- Other antihypertensives (unless prescribed as part of a combination therapy).
- Nitrates. Medications that relax the arterial walls, causing a drop in blood pressure.
- Nicotinic acid. A form of vitamin B3 used as a cholesterol-reducing drug.
- Medications for sexual dysfunction.
- 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 prior to 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.
The following substances may counteract the effects of some hypertension medications and increase blood pressure.
- Narcotics (prescription painkillers).
- Nicotine (present in tobacco products such as cigarettes).
- Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, Cox 2 inhibitors or ibuprofen.
In addition, some over-the-counter medications may adversely react with antihypertensives, including those for appetite control, asthma, colds, flu, cough, sinus problems or hay fever. People should also be careful of using eye drops for bloodshot eyes.
Lifestyle considerations with High Blood Pressure medications
When first taking antihypertensives, patients should avoid operating heavy machinery (e.g., driving) until they know how the medication will affect them. Most patients 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 no longer be effective and they may have to switch to another drug.
Patients are encouraged to continue to see their physician for regular follow-up to ensure their high blood pressure is under control, even if it appears that symptoms have been relieved. Many patients may also be asked to self-monitor their blood pressure with simple at-home equipment. This will provide information that can help the physician make treatment decisions. In addition to taking their medications as prescribed, patients may be advised to make lifestyle modifications, especially concerning diet, exercise 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 low blood pressure (hypotension).
Exposure to heat may intensify the adverse effects of hypertension medications. Patients should drink enough liquids during exercise or in hot weather and adhere to their physician’s instructions regarding exercise, activity levels and diet.
Questions for your doctorPatients may wish to ask their doctors the following questions related to antihypertensives:
- Why should I use medication to treat my hypertension?
- Will diet and weight loss help my hypertension in addition to this medication?
- What type of antihypertensive are you prescribing and why?
- I have read that some of the least expensive antihypertensive are the most effective. Why should I take a different one?
- How will antihypertensives react with my other heart medications?
- How can I tell if this medication is working?
- Would I ever need to take two different antihypertensives at the same time?
- Which type of antihypertensive will work best with my diabetes?
- Can antihypertensives help conditions other than high blood pressure?
- Which side effects are normal and which ones are serious enough to merit concern?