The names on the labels of blood-pressure bottles can seem unrelated: lisinopril, losartan, amlodipine, hydrochlorothiazide. But each is attempting only a handful of basic jobs.
Some act to relax the arteries, or remove salt and water. Others slow the heart or interfere with hormones that drive pressure upward.
The choice is rarely dictated by merely one reading taken while somebody is nervous in the clinic. Doctors take into account home measurements, age, kidney function, diabetes, heart history and the other medicines on the list.
This is also why two people with exactly the same blood pressure may receive completely different prescriptions.
Diuretics: helping the body release salt and water
Thiazide-type diuretics have been used to treat high blood pressure for decades. Hydrochlorothiazide and chlorthalidone are common examples.
They encourage the kidneys to excrete more sodium and water. A reduction in the fluid in the circulation reduces the pressure in the blood vessels. As well as this, over time, these drugs assist the arteries to remain more relaxed.
In the first few days there may be an increased need to urinate, although this becomes less noticeable. There can be fluctuations in sodium and potassium, and some people see increases in blood sugar or in uric acid, the latter of which can trigger gout in one already predisposed.
It was not until he started Lasix that the man understood why morning dosing was the preferred option. With a late-evening water pill the nights became an ordeal of trips to the bathroom.
ACE inhibitors: effective, but sometimes cough-inducing
Lisinopril, enalapril and ramipril are all part of the ACE inhibitor family.
They interrupt a hormone system which normally leads to the tightening of blood vessels and facilitates salt retention. ACE inhibitors are often beneficial in people with diabetes, kidney disease, heart failure or a history of heart attack.
A dry cough is the side effect most patients remember. It may make its appearance some time after commencing treatment, or it may creep in months later. Cough syrup will not help if this is due to the medicine.
ACE inhibitors can also raise potassium and impact kidney function, and for this reason blood tests are often done after the initiation or alteration of the dose.
Swelling of the lips, tongue or throat is rare, but serious. This reaction of angioedema is an emergency.
These medicines are not used during pregnancy, as they can damage the developing baby.
ARBs: a close relative without as much cough
Losartan, valsartan and candesartan tackle the same hormone system, but from a slightly different angle and are referred to as angiotensin receptor blockers or ARBs.
For many patients they provide the benefits of the ACE inhibitors, but are less likely to instigate the characteristic dry cough. A doctor will often switch from lisinopril to an ARB if coughing has simply become unbearable.
ARBs can also raise potassium and impact kidney function and must be avoided during pregnancy.
An ACE inhibitor and an ARB are generally not combined for treatment of blood pressure. The increased risk to the kidney and potassium levels is not deemed a sufficient trade for obtaining a small amount of extra blood-pressure control.
Calcium-channel blockers: relaxing the arteries directly
Amlodipine is one of the most widely prescribed blood-pressure drugs. It relaxes the muscular walls of arteries, allowing more room for blood to pass through.
It works well, is taken only once daily and usually does not require any complicated timing. The complaint that brings patients back is the swelling of the ankles. Socks feel tighter in the evenings, and sock marks can be the depth to photograph.
This is not always the same as retaining too much total body fluid. It is partly due to the pressure changes inside the tiny blood vessels, which allows some fluid to collect in the ankles. Taking a water pill does not necessarily solve this.
Other calcium-channel blockers, such as diltiazem and verapamil, also affect heart rate and can be used if high blood pressure appears alongside certain rhythm problems or angina. Constipation is particularly common with verapamil.
Beta blockers have more specific jobs
Propranolol, metoprolol, atenolol and carvedilol slow the heart and reduce the force of contraction.
Years ago, beta blockers were commonly handed out as a first treatment for any high blood pressure. They are now more likely to be prescribed if there is another reason to use them; previous heart attack, angina, an abnormal heart rhythm or certain types of heart failure.
They can cause tiredness, cold hands, poorer exercise performance and sometimes sexual difficulties. People with asthma must be particularly careful if one of these is prescribed, as some can tighten the airways.
Stopping suddenly is a poor idea. Heart rate and blood pressure can rebound, and angina may become worse. A taper is commonly required.
The extra medicines that appear if pressure refuses to settle
Spironolactone is frequently added for resistant hypertension, that is, blood pressure that remains high despite several medicines. It can be very effective, but potassium and kidney function need monitoring. Breast tenderness or enlargement can be seen in men.
Alpha blockers such as doxazosin relax blood vessels and can also improve urinary symptoms of enlarged prostate. They can cause a dramatic head rush when standing, particularly after the first few doses.
Clonidine lowers signals from the brain which drive upward the blood pressure. It may cause dry mouth and drowsiness. Missing several doses or stopping abruptly can cause a rise in blood pressure, so it must be handled carefully.
These drugs are useful. They simply tend to appear later or when another condition makes their use appropriate.
Why one tablet often becomes two
Blood pressure is controlled by several systems at once. Increasing one medicine to its maximum dose may produce side effects before it provides good control.
Using two lower-dose medicines which act differently can work well and feel more comfortable. An ARB may be combined with amlodipine, for example, or an ACE inhibitor with a thiazide diuretic.
Needing a second drug is not an indication that the first failed. It is often part of the treatment for hypertension.
Home readings help the prescriber to assess the outcome. Measured after sitting quietly for five minutes, with the cuff over bare skin and the arm supported. A week of sensible readings is more informative than one rushed measurement after climbing the stairs in the clinic.
Our hypertension treatment section covers many of the commonly used medicines, but the final choice is determined by more than just the number on the monitor.
The best blood-pressure tablet is not the newest or strongest. It is the combination that keeps pressure controlled without damaging the patient’s well-being too much compared to the situation before they had hypertension, which conveniently, often did not cause any symptoms.
