Which Drugs Cause Orthostatic Hypotension & Can Obesity Cause It?

Orthostatic hypotension is the condition in which there is a decrease in blood pressure one the person tries to change posture to the standing position in a short period of time. Although it can be due to various medical conditions it can also occur from the intake of various drugs too.

Which Drugs Cause Orthostatic Hypotension?

The most common group of drugs to cause orthostatic hypotension is antihypertensives. It consists of beta-blockers, Alpha-blockers, calcium channel blockers, loop diuretics, thiazide diuretics, alpha + beta-blockers, vasodilators, etc. These all are the drugs that help in reducing the blood pressure if the patient is hypertensive. But the overdose or the first dose of these drugs could reduce the blood pressure more than required.

Alpha-blockers are the most common drugs to cause orthostatic hypotension in the first dose whereas beta-blockers are the commonest to be known to cause falls in blood pressure with the change of posture also known as postural hypotension. Any diuretics be it the loop diuretics or the thiazide diuretic they cause the orthostatic hypotension by decreasing the blood volume in the body because they increase the urine production by preventing reabsorption of water from the kidneys. Calcium channel blockers reduce the muscle tone of the large vessels, as well as cardiac output, is also affected as they also have action on the working of the heart resulting in the same effect on blood pressure.

Another cardiovascular group of drugs like dopamine agonists, antianginals, antiarrhythmics, can also lead to orthostatic hypotension even when they do not belong to the antihypertensive group of drugs.(1) The drugs commonly used in psychiatric illnesses are also one of the major groups causing features of orthostatic hypotension for example antipsychotics like phenothiazines, antidepressants like monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, antidepressants, etc.

Another group of drugs known as phosphodiesterase inhibitors also functions similarly as that of vasodilators because they also cause dilation of the vessels which leads to the pooling of the blood and causes to fall in the blood pressure when a person tries to stand. The change is sometimes so severe that the person falls immediately causing syncope.

Can Obesity Cause Orthostatic Hypotension?

While asking for a question that obesity can also cause orthostatic hypotension, the answer is yes. Orthostatic hypotension occurs in overweight patients by the following mechanism. When an obese patient is lying down, there is increased pressure on the inferior vena cava due to the weight of subcutaneous fat on the abdomen. This pressure leads to compression of inferior vena cava and there is reduced flow of blood through it causing what is known as venous pooling of blood. When the person tries to stand suddenly, there is a rapid fall in venous return, in turn, leads to reduced cardiac output which may or may not is compensated by an increase in heart rate but the blood pressure falls for sure. However, this phenomenon occurs only when there is morbid obesity that is when body mass index is above 35 or 40.

But according to various studies, orthostatic hypotension is more commonly associated with lower BMI that is less than 18.5 which is normal.(2) The persons with body mass index on the lower side that is underweight persons are usually associated with down regulation of sympathetic as well as parasympathetic nervous systems. It leads to a decrease in the response by the body against the change in posture and forces acting upon the blood in a downward direction. The blood vessels are not able to maintain their tone and lead to blood collection and in turn, ultimately causes falls in the blood pressure.

Conclusion

There are various drugs as described above which can cause orthostatic hypotension and patients should be very careful while using these drugs and should consult the doctor if such symptoms appear. Obesity can also be one of the causes for orthostatic hypotension.

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