I see it now. The drug, called Petite Mort [Little Death], recreates the physical experience of being human without the sensual cues. Normally, vampires are less sensitive to pain and fatigue because they have a higher level of stamina and endurance than mortals. Petite Mort would make them more susceptible to damage without making them more sensitive to it. The drugged vampires’ senses remain vampiric, but their bodies suffer in a mortal manner without their nervous systems registering the damage.

Basically, vampires on Petite Mort are like mortals with Riley-Day Syndrome, a genetic disorder in which one of the most salient and dangerous symptoms is an inability to feel external pain. Without the cues of pain, persons with Riley-Day Syndrome experience injury and do not notice. For example, Ashlyn Blocker, a 5-year-old with the disorder, has burned herself and knocked out both child and adult teeth. She also experienced a scratch to a cornea that, I believe, reduced her vision in the affected eye. In the same manner, vampires on Petite Mort do not have human levels of pain/self-preservation, so they can give themselves fatal injuries rapidly. Furthermore, vampires on Petite Mort often overestimate their capacities and attempt to do things that would require vampiric strength, agility or resiliency.  The lack of nervous system feedback leads the drug users to overextend themselves and hurt themselves.

Also dangerous is the fact that Petite Mort makes users lose their taste for blood. They don’t want to drink blood; they want to eat human food. If they use Petite Mort regularly, they may forget to drink blood, which they must, in order to survive [because they’re still vampires]. Thus Petit Mort can lead users to starve to death.

As if these problems weren’t enough, Petite Mort has especially risky side effects those who have been vampires for longer than 10 or so years. When using Petite Mort, vampires who have been dead for greater than 10 years return their immune systems to the eras in which they died. Petite Mort does not reactivate chronic or terminal conditions [i.e., Will would not resume his asthma, nor Mark his AIDS], but it does give vampire users the immune systems that they had when human at the times of their death. Therefore, vampires who use Petite Mort are vulnerable to any new diseases that have developed since they were vamped.

So, to recap, Petite Mort lets you go out in direct sunlight and eat garlic. As a tradeoff, you’re likely to disable or kill yourself indavertently due to a decreased ability to feel pain…or starve to death…or die because of something that you weren’t vaccinated against because you were vamped before the disease developed. Sounds attractive to me! Actually, it sounds like a good way to kill vampires: drug ’em and let ’em self-destruct.