This information is for men who have erection problems. It tells you about alprostadil injections, a treatment used for erection problems. It is based on the best and most up-to-date research.
Does it work?
Yes. Injecting a drug called alprostadil into your penis can give you firm erections, whatever the cause of your erection problems. The injection should work up to 9 times out of 10. It can help you have better sex with your partner.
Alprostadil injections may be better than vacuum pumps at making you more likely to ejaculate and have more satisfying sex.
But you may not like giving yourself injections. And if you use this treatment, you may have to plan when you have sex. For this treatment to work, you need to be able to talk to your partner about what it involves.
What is it?
Alprostadil is a drug that widens the blood vessels in your penis so that more blood flows through. This makes your penis firmer.
You can take alprostadil as an injection that you inject yourself. You need to inject the drug into or near the base of your penis. You use a very thin needle so that it hurts as little as possible. Doctors call this an intracavernosal injection.
After the injection, you may need to massage your penis so that the drug gets around your penis.
Brand names for alprostadil injections include Caverject and Viridal Duo.
You can also take alprostadil as pellets that you put in your penis.
Alprostadil is not available to everyone on the NHS. For more, see Treatment for erection problems on the NHS.
How can it help?
Alprostadil injection can help by: 
Giving you an erection firm enough to enter your partner
Making you more likely to have an orgasm
Making sex better for you and your partner.
Your erection should last long enough to have sex. Most people who use this treatment find that their erection lasts about one hour after the injection.
Alprostadil injections have been compared with other treatments for erection problems.
Alprostadil injections work better than another treatment that's given by injection called papaverine.   
Alprostadil injections work just as well as injections that contain papaverine and phentolamine (sometimes called Bimix).  
Alprostadil injections work better if they're mixed with papaverine and phentolamine (sometimes called Trimix).  
Alprostadil injections work as well as sildenafil (brand name Viagra). 
Alprostadil injections work as well as vacuum pumps to help men get an erection. But alprostadil injections are better at helping men have an orgasm. 
How does it work?
Alprostadil injections have a chemical called prostaglandin E1 (or PGE1 for short). This is like a chemical made naturally by your body. It makes blood vessels open wider, so that more blood can flow through.
When you inject the medicine into your penis, it goes to work straight away on the blood vessels there. These blood vessels get wider and more blood flows into your penis, making it firmer. This helps you get a better erection, so you're likely to have better sex.