It's a powerful diuretic that removes surplus fluid from the bloodstream or tissues, and it can also prevent salt retention in patients with heart failure.
As such, it's been used to treat high blood pressure (hypertension), congestive heart failure, kidney and liver disease, and conditions where there are abnormally low levels of potassium in the blood.
Better yet, it seemed to be 'well tolerated', as doctors put it. In other words, it has side effects that aren't too worrying, and they include nausea, headache, low blood pressure, constipation, dizziness, and shortness of breath.
There had been a few rumours that it might cause stomach problems, such as ulcers and gastric bleeding, but these had never been verified.
But a new study, involving 306,000 patients taking Aldactone, has discovered that it dramatically increases the risk of gastric or duodenal ulcer - in fact, by nearly three times.
Does the risk outweigh the drug's benefits? Probably not, but at least patients know why they have serious stomach problems all of a sudden - and new patients can be told about the risks, too.
(Source: British Medical Journal, 2006; 333: 330-3).