High Blood Pressure Medication Side Effects
There are no drugs without side effects, even if they’re very mild ones. It’s important to know the side effects of a particular medication before administration, especially in cases where the drug should be taken for years, as in hypertension.
Complications of anti-hypertensive medications can be divided according to drug group as follows:
- Diuretics: loss of important ions in the urine causing what is known as an electrolyte imbalance in the body and dehydration due to the excessive loss of fluids. Dehydration should especially be avoided in patients who are old in age and therefore more susceptible.
- Alpha blockers: they lead to a phenomenon known the first dose phenomenon. The first dose of alpha blockers taken usually causes marked vasodilatation or widening of the blood vessels causing blood pressure to drop. As a result, fainting and postural hypotension may occur. Postural or orthostatic hypotension is the inability to maintain an adequate blood pressure when changing position, for example when getting up off a bed.
This phenomenon can be avoided by using a small dose to begin with and gradually increasing it or by taking the first dose before going to bed to avoid the risk of fainting and any subsequent injuries which is especially important if the patient is old in age.
- Centrally acting drugs: This group of drugs includes alpha methyl dopa, clonidine and reserpine.
Alpha methyl dopa while favorable during pregnancy is characterized by several side effects such as depression, extra-pyramidal manifestations (involuntary movements as in Parkinson’s disease) and autoimmune mediated conditions such as autoimmune liver disease.
Clonidine is a drug that decreases sympathetic discharge but at the same time causes salt and water retention, so its use should be accompanied by diuretics to counteract this side effect. It may also cause a rebound increase in blood pressure once it is stopped.
Reserpine is no longer used because it has been found to deplete nerve endings of their stores of noradrenaline (norepinephrine). In addition to this effect, it has also been found to cause depression, extra-pyramidal manifestations and nasal congestion.
- Vasodilators: These include three groups; vein dilators (venodilators), arterial dilators (arteriodilators) and drugs which dilate both veins and arteries.
Calcium channel blockers, which belong to the group of arteriodilators, include a drug known as minoxidil which causes hypertrichosis or excessive growth of body hair. Some of these drugs also cause a marked decrease in heart rate.
Sodium nitroprusside is a drug which dilates both arteries and veins. It may cause cyanide or thiocyanate toxicity in case of liver or renal disease, respectively. This is because these are metabolic products of the drug and will accumulate leading to toxicity in case of inadequate secretion if either the liver and/or the kidneys are affected.
Angtiotensin converting enzyme inhibitors (ACE inhibitors) are also a group of drugs that dilate both arteries and veins. While potent and very beneficial, they have side effects like any other drug such as electrolyte disturbance (particularly an increase in the level of potassium in the body), skin rash, renal affection and the development of a chronic dry cough.