There seem to be a lot of different medications on the market for raised blood pressure. Why have I been given one and not another?
There are various types of medications in common use. Table 2.2 lists the most commonly prescribed medications for raised blood pressure and Table 2.3 lists some of their possible side effects. The drugs have a generic or chemical name and a trade name under which they may be marketed. The trade names vary between countries so always check against the generic name to make sure that you are on the recommended medication.
Diuretics or 'water tablets' are commonly used. They remove excess salt and water from the body. They can also wash out too much potassium (and this may cause cramps) which can be dangerous if digoxin is also being taken. In some people, diuretics cause gout, and if you have diabetes they can raise your blood sugar, upsetting control of your diabetes. Common medications in this group include bendroflumethiazide, indapamide (Natrilix) and chlortalidone (Hygroton) To reduce the loss of potassium, so-called potassium-sparing agents can be prescribed and these include spironolactone, triamterene or amiloride. These two sorts of medications may be combined, as in Aldactide, Moduretic or Dyazide, in order to try and get the best results. Diuretics in general are safe and effective and side effects are not common. Fresh fruit is a good way of replacing potassium - a banana a day may do the trick.
Beta-blockers are now less frequently prescribed. These act to slow your heart rate and lower your blood pressure by blocking the effects of adrenaline. Commonly used medications are atenolol (Tenormin), metoprolol (Betaloc, Lopresor) and bisoprolol (Cardicor). The commonest side effects are cold hands and feet, heavy legs, lethargy and a 'zombie-like' feeling. Beta-blockers may cause wheezing and are not used in people with asthma. They may also hide the signs of a low sugar level in people with Type 1 (insulin-dependent) diabetes. They do not tend to mask the perspiration that goes with a hypoglycaemic attack (low sugar episode), so this warning sign is preserved. If the diabetes is stable and well controlled, they are used, but more often if there is also angina present (see Chapter 3).
As a group, the beta-blockers are useful medications, and although they are no longer first line, if you have had a heart attack you may live longer if you are prescribed them. They can be combined with diuretics for an additive effect and may be available with a diuretic in a single tablet, such as Tenoretic.
Calcium antagonists act to expand the arteries, making it easier for blood to flow (like widening the hose pipe). They can be used with diuretics and some can be used with beta-blockers. The exception is verapamil (Securon, Cordilox, Univer) as the heart rate can get dangerously slow. Calcium antagonists are helpful if you have asthma, and do not affect the medications that you may be receiving if you have diabetes. Commonly prescribed medications are amlodipine (Istin), diltiazem (Tildiem, Adizem, Dilzem), nifedipine (Adalat), verapamil (Securon) and felodipine (Plendil). Side effects include water retention (causing swollen ankles and legs), headaches, constipation (especially verapamil), occasional palpitations and sore gums. Impotence is unusual. Again these are useful medications which seem to be of more value in the elderly and African-Caribbeans. Older people and African-Caribbeans have a different hormone pattern from the kidneys, which makes calcium antagonists more effective.
ACE inhibitors and angiotensin II (AII) antagonists are widely used. ACE stands for angiotensin-converting enzyme. This enzyme is normally present in the body; blocking it causes the blood vessels to relax (the blood pressure falls as it meets less resistance) and reduces salt and water retention. Angiotensin II antagonists act in the same way but at a different point from ACE inhibitors - the end result is the same but the cough side effect of the ACE inhibitors (see below) is usually avoided.
ACE inhibitors include captopril (Capoten, Acepril), lisinopril (Carace, Zestril) and enalapril (Innovace), whilst the Alls include losartan (Cozaar) and valsartan (Diovan). They both act much the same way by blocking chemicals that constrict the arteries and retain salt and water. If you have heart failure, ACE inhibitors and AIIs can lengthen your life and can protect people with diabetes from kidney damage. The main side effect is a dry hacking cough. These are important medications which have few side effects and are not known to interfere with your quality of life. AIIs do not usually cause problems with men's erections. ACE inhibitors have recently been shown to benefit patients with coronary artery disease in the absence of high blood pressure or heart failure.
Alpha-blockers act on nerve receptors to dilate the arteries - this in turn lowers the blood pressure. Prazosin (Hypovase) and doxazosin (Cardura) are the most common ones. They can cause tiredness and dizzy feelings. Their major advantage is the reduction in prostate symptoms in a man. They can be combined with all the other medications and are safe in people with asthma or diabetes.
Renin inhibitors are a new class of drugs that inhibit renin, a kidney hormone. Aliskiren (Rasilez) is now available and acts like ACE inhibitors and AIIs, relaxing the arteries. Diarrhoea can occur and checks on kidney function and blood tests for potassium are advised. Its role at present is limited.