Medication

Diuretics

Diuretics help the kidneys get rid of excess salt and water. they are often the first-line treatment for hypertension. They are also especially helpful for treating patients that apart from hypertension have heart failure, isolated systolic hypertension, the elderly, and patients with diabetes.

Results of a recently performed, large study have suggested that diuretics work just as well as newer drugs in lowering blood pressure and are even more effective in preventing heart failure, stroke, and heart attacks.

There are several types of diuretics, some need to be taken once a day, some need to be taken twice a day.

Thiazides: these include bendrofluazide, chlorothiazide, chlorthalidone, indapamide and hydrochlorothiazide. These drugs are amongst the oldest we use. They cause the kidney to release more salt, but also potassium, with the urines, but the diuretic effect (amount of extra urine you produce) is minimal. In most cases these are the diuretics of first choice. side effects are mainly an increase in blood sugars (so not so good for diabetics) and a tendency to cause gout. Some people claim they cause erectile dysfunction.

Potassium sparing diuretics: mainly amiloride, spironolacton and triamterene. These drugs also have a minimal diuretic effect, but make the kidneys lose salt, whilst at the same time they retain as much as possible potassium. in patients with kidney failure these drugs can be contra-indicated as they can cause a high potassium level in the blood.

Loop diuretics: Typical examples: frusemide and bumetanide. These are very strong diuretics with a very short acting duration. They are very useful in patients that retain a large amount of fluid (oedema: swollen legs) or are short of breath because of fluid ‘around the lungs’. Their efficacy is at the same time a problem, as they can dehydrate patients, they can cause significant potassium loss and are often difficult as the effect can be so strong that especially older people may experience incontinence. They should not be taken before bedtime as the effect will disturb the sleep.

Beta Blockers

Beta blockers help slow heart rate and lower blood pressure. They are often used in combination with other drugs, such as ACE inhibitors (see below) and diuretics. Beta blockers are more likely to be used to treat hypertension in patients with angina (chest pain), previous heart attacks, heart failure, problems with a too fast pulse rate or migraine headaches.

typical examples of beta blockers in New Zealand are: metoprolol (Betaloc), carvedilol, atenolol and celiprolol. they differ a little in their effects and benefits, depending on the situation of the patient.

There are some issues with beta blockers too. They should never be abruptly stopped and the slow down effect that they have on the heart rate may rebound and cause a rapid response with fast heart rates (tachycardia) and increase in blood pressure. Stopping abruptly can in that phase than even cause a heart attack or a stroke. They can also cause a worsening of asthma symptoms and increase sometimes the choletsreol (blood fat) levels. In patients with diabetes they sometimes takes away (mask) the early warning signs our body gives when the blood sugar levels drop too low. Other common side effects may include fatigue, less energy to do physical exercise, vivid dreams and nightmares and cold hand/feet. Also beta blockers are said to cause problems with sex drive (libido) and erectile function.

Talk to your doctor about the side effects, and never stop the drug simply on your own behalf.

ACE Inhibitors

Angiotensin-converting enzyme (ACE) inhibitors have become very important drugs in todays treatment of hypertension. they open blood vessels and decrease the workload of the heart. They treat bloodpressure, but also protect the kidneys (by reducing the pressure in the 2 million tiny filters in the kidneys) and the muscular wall of the heart.

patients with heart failure, especially those with an enlarged heart, previous heart attack, diabetes or kidney disease are considered good candidates for ACE inhibitor treatment and for them this drug is usually first choice. A large study reported that patients with diabetes who took these drugs had fewer heart attacks and lower overall mortality rates than patients who took other types of high blood pressure medications. Interestingly in both treatment groups the bloodpressure was equally well controlled, showing that other factors, apart from blood pressure itself play an important role. ACE inhibitors are also known to slow worsening of kidney failure once that is diagnosed, and is for this purpose also used in patients that have a completely normal bloodpressure.

In New Zealand ACE inhibitors commonly used are: quinapril (Accupril), cilazapril (Inhibace), captopril (Capoten). They are sometimes used in combination with a diuretic (especially hydrochlorothiazide), and this substance can even be melted in one tablet with the ACE inbitor, then called Inhibace plus or Accuretic.

An important side effect of ACE inhibitors is dry cough. Thid happens in 10-20% of the paople using it. After stopping the ACE inhibitor this stops after about a week. In this case we usually switch to a Angiotensin Receptor Blocker (ARB): see below. What we also can see are more than expected blood pressure drops. In some patients ACE inhibitors cause a high potassium that can be dangerous if there is already a high potassium because of co-existing kidney disease. For this reason ACE inhibitors are usually not used in combination with potassium sparing diuretics. A rare, but potentially dangerous side effect is an allergic reaction, called angio oedema with severe swelling of the face and occasionally of the airways. Luckily this is extremely rare.

ACE inhibitors should not be used in pregnant women or whilst breatsfeeding. If there is a desire to become pregnant, it is usually advisable to switch to another class of medication.

Angiotensin-Receptor Blockers (ARBs)

This class of drugs is a newer development of the ACE inhibitor class, but has fewer and less severe side effects. The working mechanism is the same but the drug works directly where its action is desired, instead of having breakdown products in the bloodstream. In general, ARB’s are prescribed in patients who do not tolerate ACE inhibitors. Pharmac will in New Zealand only allow doctors to use ARB’s (they are more expensive than ACE inhibitors) if they have a proven negative reaction (side effects or not enough action on the bloodpressure) with an ACE inhibitor.

The names of the ARBs used in New Zealand are: candesartan (Atacand) and Losartan (Cozaar). Like ACE inhibitors, they can be combined with a diuretic or have them combined in one tablet (Atacand Plus or Hyzaar in this case).

The side effects are similar to that of the ACE inhibitors, but the well known cough is extremely rare, as are allergic reactions. the contraindication in pregnancy is similar to that of ACE inhibitors.

Calcium-Channel Blockers (CCB’s)

This class of drugs exerts its major effect by relaxing blood vessels. recent research has shown that newer types of drugs, like CCB’s but also ACE/ARB’s, may be a better treatment option for middle aged patients. in the elderly CCB’s have the disadvantage that they may the relax the (stiffer) blood vessels so much, that unexpected bloodpressure drops may occur. These patients are often better treated with a diuretic.

Typical drugs of this class in New Zealand are felodipin (Plendil) and amlodipin (Calvasc). If there are also problems with the rhythm of the heart we may use a CCB that has quite different modes of action, called diltiazem (Cardizem) and verapamil (Isoptin).

Although CCBs are often a friendly class of drugs, side effects may include swelling of the ankles (the blood vessels in the legs open too much and some fluid is reatined in the lower legs), constipation and fatigue. Sometimes people report flushing in the faces (little bloodvessels in the face opening). There are some food interaction with CCB, changing their mode of action. This is particularly strong with grapefruit juice and some orange products).

Alpha Blockers

This is a very different class of drugs. they block a receptor that looks a little like the beta receptor (see beta blockers), but the alpha blockade leads to a more prominent widening of the bllod vessels. In contrast to the beta blockers they do not slow down the heart rate. This class has side effects (dry mouth, unexptected blood pressure drops and dizziness) that make it a less popular drug for first line treatment. Often we strat a very low dose and carefully move upwards with it, guided by the effect on the blood pressure and the side effects. The alpha blockers can work well in the elderly and in patients with kidney disease, especially for those on dialysis. Another, unrelated benefit is that these medications are able to shrink the prostate a little in elderly men with an enlarged prostate. Sometimes this is just enough to prevent prostate surgery.

Typical examples of alpha blockers in New Zealand are doxazosin (Cardura) and terazosin (Hytrin).

Vasodilators

The main effect of this class is a quite strong opening of the blood vessels (vasodilatation). The smooth muscle cells in the blood vessel wall are ‘paralyzed’ and the blood vessels open widely. The effect can be very strong and lead to significant side effect. Although popular in the United States, this drug class never really made it to our shores. If used, we often do it in combination with a milder drug, like a diuretic or a beta blocker, in order to keep the dose as low as possible. Examples of this class are clonidine (Catapres), Minoxidil (Loniten) and hydralazine (Apresoline). In patients with angina (chest pain) and heart attacks these drugs should be used with extreme caution.

Centrally working agents

This class of drugs is perceived by many as ‘old fashioned’ or obsolete. in reality however we can see remarkable successes, especially in the elderly mild relatively mild hypertension. the drugs are tolerated well. We do not know much how they exactly work, but the signal to lower the blood pressure comes from the central nervous system (brain). This explains the side effects that can include headaches, and vivid dreams or nightmares. The only available drug in this class is alpha methyl dopamine.