If you give a slave too much faerie pollen it takes quite a while for them to recover. If they fall unconscious you can:
a) let them stay in coma until they recover, at cost of an active slot (optimal: pig in barn with S+ nurse-skill farmhand to feed her and keep her alive)
b) revive at medical center and then have them do athletics (supplementing with ambrosia can help to get their endurance high enough to get into a sustainable pattern of exercise, as well as giving supplements, nutritionist or calculated diet, using kamra sparingly [less harmful], raising their mood, ensuring they have a good teacher, and dressing them in sneakers and leotard) enough times each day to overcome the lingering damage
c) do b only long enough to prepare them for a quick sale
d) just give up and get rid of them
Assistants also may help themselves to your supply of drugs they are addicted to, which will harm endurance faster, so don't let them be assistants while recovering unless you've used up your supply of the drugs they crave.
When you purchase faerie pollen from the shop, the text below changes to this:
View attachment 4001856
Also the medical exam will tell you if a slave is addicted. So not that obscure. Knowing how to manage it? It's just a stat dropping, which can be raised in various ways with various degrees of efficiency. Endurance can be raised very quickly and then maintained. The higher the endurance, the more energy the slave has and the more exercise she can do each day, so you can reach an equilibrium where she is able to maintain her rehab and also do other work for you.
Ultimately, using faerie pollen heavily is like taking a loan of time from the future. It has to be paid back eventually if you want to keep that slave.
This is one of the reasons that the Eternal Rome has such a constant demand for new slaves. Most of them are used up and disposed of in short order. Tragic.