Propranolol is a drug used to treat high blood pressure. It is in a class of antihypertensive medications known as beta blockers, due to its activity against what are known as beta-adrenergic receptors. These receptors are a component of the sympathetic nervous system, which governs our body’s “fight or flight” response. By blocking these beta-adrenergic receptors, beta blockers lower blood pressure. However, propranolol––as well as several other beta blockers––have been shown to have an anti-cancer effect.
Beta Blockers and Cancer
Epidemiological studies on men taking drugs for high blood pressure found that those taking beta blockers had a lower risk of developing prostate cancer. Further studies found that cancer patients taking a beta blocker have a lower risk of cancer death.
This brings up a very important point regarding the link between stress and cancer: why would a blood pressure drug reduce both cancer development and cancer death? The answer lies in the mechanism of how these drugs work in the body. By reducing the “fight or flight” portion of the nervous system, the stress––or perceived stress––on the body is greatly reduced. This reinforces our long-held belief that stress plays a role in cancer. In fact, a recent study confirmed that stress-induced activation of the neuroendocrine system resulted in a 30-fold increase in cancer spread!
Propranolol’s anti-cancer effect extends beyond its effect on the stress. Research has shown that propranolol has an effect on cancer cell proliferation and invasion. It also stimulates the immune system, and has been shown to inhibit angiogenesis (formation of new blood vessels to feed cancer). Finally, propranolol seems to improve sensitivity of cancer cells to other treatments such as chemotherapy, thereby improving the results of those therapies.
Because it lowers blood pressure, it goes without saying that we must be careful in our use of propranolol. It is likely not ideal in patients who tend to have low blood pressure. However, for those without tendencies toward hypotension, it is generally very well-tolerated. In fact, in patients who are already under a lot of stress, propranolol often makes patients feel that a significant load has been lifted off of them, leading to improved energy levels and a better quality of life.