As with all medicines, there are possible side effects with antihypertensive medicines. Some of these side effects can occur with all high blood pressure medications. These include dizziness, lightheadedness, allergies, and gastrointestinal distress. In addition, there are side effects that only occur when taking a specific type of medication. For example, beta-blockers and diuretics can affect blood sugar levels and blood lipid levels, whereas a typical side effect for calcium antagonists is flushing – a reddening of the facial skin.
Diuretics are well tolerated
ACE inhibitors may occasionally cause an irritating cough due to dilation of the vessels in the larynx. In isolated cases, this can lead to respiratory distress due to laryngeal swelling as part of an overreaction. These side effects occur much less frequently with AT1 receptor antagonists. They are also generally better tolerated. They are therefore a popular alternative to ACE inhibitors. When treated with calcium antagonists, side effects such as headache, ankle swelling, muscle cramps, and a feeling of warmth with facial redness (flushing) are common. The nifedipine-type drugs may cause an increase in heart rate (tachycardia). In contrast, treatment with verapamil and diltiazem may cause a slowing of the heart rate (bradycardia). Diuretics are generally well tolerated. Possible side effects include disturbances in mineral balance such as a drop in blood potassium or sodium levels and muscle cramps. Rarely, there is an increase in blood sugar or cholesterol levels. In addition, the use of diuretics can increase uric acid levels in the blood, which can trigger an attack in gout patients.
Beta-blockers: not suitable for asthmatics
Most beta-blockers should not be used by patients with asthma. This is because beta-blockers also have a small effect on the beta2 receptors on the bronchi, which can cause bronchoconstriction. In addition, beta-blockers may cause the following side effects:
- The effect of beta-blockers on the heart may cause a slowing of the heart rate (bradycardia) or cardiac arrhythmia.
- In addition, they affect the metabolism and can therefore lead to an increase in blood sugar and cholesterol levels in the blood.
- Other possible side effects of beta-blockers are potency disorders or circulatory problems in the hands and feet.
For a complete list of all possible side effects, see the package insert for your medicine. If you experience side effects during treatment with an antihypertensive medication, you should contact your doctor. He or she will discuss with you whether it makes sense to change the medication in order to treat your high blood pressure with as few side effects as possible.
High blood pressure medications: be careful if you have diabetes
Treating high blood pressure is especially important in patients with diabetes, because elevated blood sugar levels along with high blood pressure greatly increase the risk of damage to organs and blood vessels. However, not all medications for high blood pressure are suitable for diabetics:
- Beta-blockers can stimulate the breakdown of sugar storage in the liver, leading to an increase in blood glucose levels.
- Thiazide diuretics, on the other hand, cause a decreased release of insulin, which can exacerbate diabetes.
Therefore, beta-blockers and thiazide diuretics should be used with special caution in patients with diabetes.
Hypertension therapy in pregnancy
Treatment of hypertension is also very important during pregnancy, because high blood pressure increases the risk of preeclampsia (pregnancy poisoning). However, the use of antihypertensive drugs during pregnancy carries the risk of insufficient blood supply to the placenta, resulting in an undersupply of blood to the unborn child. The consequence is a lower birth weight of the child. This is particularly the case when taking thiazide diuretics, so these drugs should be avoided during pregnancy. As with all medications, it must also be borne in mind that the active ingredients can pass into the child’s circulation via the placenta – or via breast milk if the child is breastfeeding.For this reason, ACE inhibitors and AT1 receptor antagonists must not be used during pregnancy or while breastfeeding. This is because they can cause kidney failure in unborn babies and infants.
Side effects depend on stage of pregnancy
Calcium antagonists are unsuitable in the first three months of pregnancy because they have caused malformations in animal studies during this period. However, in advanced pregnancy, nifedipine-type calcium antagonists may be an option in the treatment of hypertension. After the third month of pregnancy, certain beta-blockers such as metoprolol can also be used to treat hypertension. In addition, there are medications with the active ingredient dihydralazine that cause the vessels to dilate in an as yet unknown way, thereby lowering blood pressure. These are considered safe in late pregnancy.
Alpha-methyldopa: safe in pregnancy
However, the agent of first choice throughout pregnancy is alpha-methyldopa, which decreases the release of norepinephrine. The neurotransmitter normally causes blood pressure to rise via constriction of blood vessels and increased production of angiotensin-II. By reducing the concentration of norepinephrine, alpha-methyldopa effectively lowers blood pressure. The drug’s safety in pregnancy has been demonstrated in numerous studies.
Therapy resistance: when blood pressure won’t go down
If blood pressure is still too high despite combination therapy and consistent use of the drugs, the doctor can prescribe so-called reserve drugs. This is the name given to strongly effective medications, but because of their numerous side effects, they are prescribed only when other medications do not have sufficient effect. In cases of therapy-resistant high blood pressure, the two active ingredients doxazosin and minoxidil are used:
- Doxazosin: The active ingredient blocks alpha1 receptors on vascular muscle cells. Thus, doxazosin prevents norepinephrine from binding to these receptors and causing vasoconstriction. Since doxazosin acts directly on the vessels, the blood pressure-lowering effect is much stronger than with other drugs for high blood pressure. However, this also leads to more frequent severe side effects: Patients often complain of dizziness and lightheadedness to disturbances of consciousness when standing up too quickly.
- Minoxidil: This active ingredient causes an outflow of potassium from the vascular muscle cells, whereby the vessels are greatly dilated. This leads to a rapid reduction in blood pressure, but the body responds with a counter-regulation: there is an increase in heart rate and water retention in the legs. To mitigate these side effects, patients usually have to take an additional beta-blocker and a diuretic.
