Spironolactone is an antiandrogen that is often used in feminising hormone treatment to suppress testosterone. As well as suppressing the production of testosterone, spironolactone has some oestrogen-like effects, which makes it a very effective antiandrogen.
As well as its antiandrogenic effect, spironolactone relaxes the blood vessels in the body, which lowers blood pressure.
While the majority of people who take spironolactone tolerate it without complications, some people on spironolactone exhibit significant decreases in blood pressure. This is known as hypotension.
Hypotension is potentially dangerous, because it can decrease blood flow to vital organs, including the kidneys, heart, and brain. This can increase the risk of kidney impairment, as well as cause symptoms such as fainting, dizziness, headache, and fatigue.
For this reason, spironolactone is contraindicated in people with hypotension. Also, people who are taking spironolactone are required to have regular blood pressure checks to monitor for hypotension.
The measurement of blood pressure involves two numbers. The first number is called the systolic pressure, which is the blood pressure when the heart is contracted. The second number is called the diastolic pressure, which is the blood pressure when the heart is relaxed.
While blood pressure varies significantly between people and can fluctuate throughout the day for various reasons, a healthy blood pressure is considered to be between 90/60mmHg and 120/80mHg.
A blood pressure below 90/50mmHg is commonly considered to indicate hypotension, and so spironolactone is not recommended in this range.
If your blood pressure is below 90/50mmgHg, then spironolactone is not recommended for you. If you are taking spironolactone and you have hypotension, it is recommended that you stop taking spironolactone and instead consider a different antiandrogen.
If you have had to stop spironolactone because of hypotension, alternative antiandrogens are available which do not affect blood pressure. These include gonadotropin releasing hormone analogues (nafarelin, triptorelin, leuprorelin), 5-alpha reductase inhibitors (finasteride, dutasteride), and cyproterone acetate.