Male readers, would you risk your life for an erection?
It seems like a bizarre (and personal) question, but there are patients that are more than willing to do it. They are so willing, in fact, that they will lie to both doctors and pharmacists to get their hands on little blue pills when it's the little white ones that are keeping their heart supplied with oxygen.
Viagra, Cialis, and Levitra belong to a class of drugs called PDE-5 inhibitors. PDE-5, otherwise known as phosphodiesterase isoform 5, is an enzyme indirectly responsible for maintaining the amount of free nitric oxide, or NO, in certain parts of the body. PDE-5's claim to fame is that it decreases the amount of NO in the vasculature of the penis in an area called the corpus cavernosum. NO causes blood vessels to expand, which in turn causes an erection. By blocking PDE-5, the overall concentration of NO goes up, making it easier to achieve erection--but not in the absence of sexual stimulus (typically, anyway). If you want some good anatomical diagrams, try this link, which coincidentally explains more or less exactly how these drugs work in more detail.
Nitroglycerin and other nitrates work on the NO system, too. All of these drugs either directly degrade into NO or indirectly release NO via metabolism in the bloodstream. Angina pectoris (chest pain) is caused by the heart receiving insufficient oxygen. In the treatment of angina, NO causing expansion of blood vessels allows more blood to flow to the heart. It also decreases the pressure in other vessels, making it easier for the heart to pump blood; because the heart is not working as hard, it needs less oxygen. The result is a reduction in angina symptoms.
Both of these drugs increase NO levels. NO dilates blood vessels. Can you see where this is going?
Yes, combining nitrates with PDE-5 inhibitors can result in so much dilation of blood vessels that blood pressure drops to dangerous levels. If pressure drops too low, vital organs (such as the brain) can become starved of blood--which means that they are also starved of oxygen.
This drug combination is therefore contraindicated, i.e., a totally bad idea--and the kind of thing that a doctor (or more likely a pharmacist) could get sued for prescribing/dispensing. Giving a patient on nitrates a drug for ED is putting the patient at serious risk. But I've encountered patients who were willing to lie to everyone within a five-mile radius--doctors, nurses, technicians, pharmacists--to get their hands on the blue pills (or yellow ones, depending on their preferred drug).
The whole scenario raises some interesting questions. Why are male patients willing to lie to their healthcare providers? Perhaps they don't really understand the risk. Perhaps they think they understand the risk, but they don't care. Perhaps they're being fed all kinds of mass-marketing and commercial nonsense about how they'll never be able to satisfy their lovers without Big Pharma's magic erection pills. ED is a serious quality of life issue for a lot of patients--those with diabetes are among the most commonly affected. But when we as a society are putting pressure on men to the point where they are willing to risk their lives to get a hard-on, something is wrong. And this pressure isn't new--the search for aphrodisiacs has been on ever since the start of recorded history. A biological imperative? A product of culture? Who can say for sure?