Sildenafil 25mg

You got my attention, lad. I am now looking for remedies other than sildenafil and tadalafil. 5/5

At the risk of also being called a lair, my husband developed a similar reaction with a drug called sildenafil. The first time he tried it, it took about 3 to 4 hours to loose his erection.

C'mon, Doc...Viagra ( Sildenafil ) was developed to lower blood pressure and help prevent heart attacks! It was only discovered later that it has the benificial side effects that have made it famous today. His wife probably helped prevent him having a coronary even earlier than he did.
Great story though....

Like you I’ve found it needs no more that a quarter of a Sildenafil tablet to give me an erection as steel hard as when I was 16, and which stays up ready for another go even after I’ve jerked one off! Read my “Viagra Powered” for an interesting side effect of Viagra I discovered.

That's a very dangerous path the story is going. I think the couple is doomed. Even after just 3 days of having H and other highly addictive drugs Emily will be seriously addicted to the high and her brain will do almost anything to get the endorphines again and again. She will deny herself sleep, eat and drink to get this combination of the rush of the drug and the even higher endorphine rush of the triggered orgasm while injected. At the end of this chapter it was mentioned that, at the first time, she was given 10mg of H and after only a couple of days she gets 400mg a day. After the scene on the street it was mentioned that a dose of 25mg had been the highest given until that time. Even at 25mg each shot that would be 16 shots of H a day or one shot every 90min. Please reconsider this in the next chapters or the Story will lose the last bit of reality that is left.

A delightful tale, well written - and a nice 'twist' on the old 'snowbound at Christmas' theme! I gave this one a solid '5'.
To the commenter (Sex4lf57?) who said that Viagra doesn't work this way, I'll toss at least a cautionary comment or two.
Viagra is derived from a medication (sildenafil citrate) that was originally designed for cardiac patients. To prevent stress on the heart (that can cause a heart attack), the chemical causes the capillaries in the body to open as wide as possible, allowing the blood to flow freely with less pressure being applied by the heart.
As such, it also opens the capillaries in the corpus cavernosum of the penis, which leads to an erection. Now, there's a 'valve' that limits blood flow to the penis, so as to allow urinary function, without urine being able to seep into the passages where sperm travels. When a guy urinates, the semen passages are cut off - and when he is erect, the urinary tract is cut off, because the urethra (tube in the penis) does double duty.
When there is sufficient erotic stimulus to cause that 'valve' to switch the seminal tract to 'open', it also opens the sphincters that control blood flow to the penis, so that the capillaries can inflate completely.
During the years (nearly 60) that sildenafil citrate has been in use in cardiac patients (under another drug-name), it was noticed that when a patient was taking the drug, he was more susceptible (at an older age) to more-solid erections. Gradually, the doctors prescribing the drug got 'field reports' from their patients, and forwarded them to the company that makes the drug. Its use as an ED drug is secondary, and took a long time for FDA approval to market such a drug to non-cardiac patients.
When the person taking the drug is in their late teens or early 20's, and has a quite healthy circulatory system - and is around a near-continual erotic stimulus, as is the main character in this story - the effect CAN be a near-perpetual erection. Even the attempts to diminish it by masturbation won't necessarily cause it to go down, when there is a hotly-desired woman present and making subtle erotic comments to the male.