Well, ideally, you should get whatever Affini who poisoned your patient to cut it out.

If there are no Affini nearby, you can do standard supportive treatment for a poisoning: IV fluids, monitoring for seizures, etc. If the patient has a haustoric implant, the implant is likely pumping more Class Ps into your patient's system. Monitor to see if they're coming out of it on their own, and if not you can apply thus-and-such pressors to counteract the Class P, an effect something like putting down the gas and the breaks at the same time. 

Clinical factors explain that Class P drugs are remarkably safe for baseline humans and don't interact with any common recreational drugs or worsen any health problems. However, they interact extremely badly with xianxiahumans. Quendi patients are likely to die immediately upon application of a Class P. While normally Class Ps work fine on Golarion gnomes, when given to a gnome in liver inflammation, they cause severe jaundice. DO NOT MIX CLASS Ps WITH PAN GALACTIC GARGLE BLASTERS. And so on and so forth. 

Well, he has no good way to tell if this person is a xianxiaworld human. Other than the fact that monitors are not beeping that angrily, he supposes. 

He'll give him three hours of IV fluids and monitoring, and if he hasn't improved then, then the pressors comes out. 

Yeah three hours of IV fluids aren't helping. 

(In the meantime Bar helpfully assigns him six starving, variously injured children from something called a "Hunger Games.")

...the patient may have gotten left for a little over three hours, on account of being stable and not worrying, and doesn't require treatment for blunt force trauma or anaemia or avoiding refeeding syndrome. 

Though now the children are the relatively stable ones, and he can spend sometime dealing with a patient who's body has the gas and brakes on while simultaneously riding the clutch. The pressors go on board. 

"Bwuh?" Cayden says. 

Everything in the world is inexplicably terrifying and his muscles are so tight and also he doesn't want to move at all but he can move which is better.

Yes, that's a patient who's had a pharmacological sledgehammer applied to them. ...pharmacological un-sledgehammer. 

"How are you feeling?" (Orientation questions can be asked later. He does not expect a sensible answer to 'do you know where you are?' anyway.)

"Like complete and utter shit. Which is novel."

Coherence! Joy of joys, the patient seems to be at least a little with it! "This is one of the better places to feel like that. You're in the infirmary at Milliways. Do you know how you ended up here?" 

"Your records will probably be a better source of information than my memories? They're... kind of a sieve, you know, because of all the xenodrugs."

"Not that I'm criticizing the xenodrugs! I appreciate all the Affini have done for me."

"You walked through a door and immediately fell unconscious. Which is why I am going to highly reccommend you stop taking them." 

"If you're... sure...?"

"You collapsed as soon as you walked into a room." And are going to be dealing with going cold turkey off a drug you should really ramp down, why did he even do this? "I am sure." 

He looks like he's going to say something and then he shuts up.

"I cannot actually stop you. Not once you're steady enough on your own feet to leave. But you did give me the sort of tox screen that I have to say something about." 

"You can stop me. Or-- your Affini can, or my Affini--"

Ah, one of his favourite talks to have with his patients, the 'I do not own slaves,' one. "I don't own an Affini. I don't own you, either." 

"Obviously. Affini own humans, not the other way around."

He runs over the list of drugs in the light of that information. That is certainly a set of implications that he is going to be neutral about, so he doesn't scare a patient who thinks he's owned and who has just taken several pharmacological bricks to the face. "I'm not owned by anyone. And while I can't say there are no Affini here-- this place takes all sorts-- I can say that none will have to get involved."