Millions of dollars in direct-to-consumer advertising by big pharmaceutical companies have ensured that most Americans are familiar with the “Little Blue Pill” — Viagra — as well as with competing products Cialis and Levitra. These drugs, called phosphodiesterase inhibitors, enhance the effects of nitric oxide, a chemical that relaxes muscles in the penis. This increases blood flow to enable an erection to occur with proper stimulation.

There are differences among the three medications, but they are relatively minor. Viagra came on the scene first, so it’s helped more people and has a longer track record. Levitra begins working the fastest, and Cialis lasts the longest — up to 36 hours, compared to four for Viagra.

Often, a doctor might prescribe one of these three pills for you, and if you don’t respond, they will switch you to another. But what happens if Viagra, Cialis and Levitra all fail for you? Or what if you have one of the conditions that don’t allow you to take ED pills — such as heart problems, high blood pressure or diabetes?

There’s actually an effective alternative that relatively few people know about — because it’s been scarcely advertised. It’s called alprostadil, which can be sold as Caverject, Edex or Muse. Alprostadil is a synthetic version of prostaglandin E, a hormone. Like the better-known pills, it relaxes muscle tissue in the penis to enhance blood flow. It even works faster than the pills — in as little as five minutes.

The downside to alprostadil, relative to the oral treatments, is how it’s administered: by needle or suppository. The needle-injection therapies, Caverject or Edex, are generally preferable, because it is a very fine needle and there is little or no pain. It’s also easy to administer yourself.

The suppository treatment (Muse) requires inserting a dosage of alprostadil, about half the size of a grain of rice, into the tip of your penis. Administering Muse can be a little painful.

If you’ve been getting your ED information only from watching TV commercials, we hope we’ve shed light on some options you might not have known about. One of the things I’ve feared, with all the attention devoted to Viagra and Cialis, is that men with ED will downplay their histories of heart disease or other risk factors in order to get their doctor to write a prescription for them. I’m sure this has happened thousands of times, unfortunately.

Now you know you don’t have to take that kind of risk. Ask your doctor about alprostadil as an alternative to the Little Blue Pill.