He's got you running round after him, checking up on him and worrying. This is wrong. It puts you on the back foot, him in the driver's seat.
I agree he's acting impulsively (to a certain extent) and it's dangerous. However, I think he needs to get the message somehow that this is NOT acceptable and he has to take personal responsibility for managing his own illness, and not turn treatment into a game, or tug of war with you.
So what I recommend - talk to his doctor (or whoever you need to regarding his medications) but you've got to come down heavy and firm on this, using the medical system on your side. (I agree - forget relying on the legal system, especially if you've lost faith with them). See if you can organise blood levels to be done to determine if he's actually taking his medications or not. If this means inconvenient and painful daily blood tests, well whose fault is that? Certainly not yours.
He needs a good talking-to, to give him every chance to tell you if the medications make him feel weird, or if he has some other problem with them. He needs to know that if he has a genuine problem, he CAN talk to you about it to see if there is some other way around a problem. Maybe there's a liquid form he can take (harder to cheek) or some other form he can't weasel out of so easily. Or maybe a different form that doesn't make him feel weird, or doesn't taste so awful. We went through similar things with difficult child 1 when he was about this age - he wanted to be 'normal' and was skipping his medications to see if he could cope without them. He was trying to say, "I'm normal, I don't need these medications, I've grown out of it, I'm fine. It's everybody else who has a problem." He needed to find out that the medications WERE beneficial, even if he couldn't notice any difference in himself. What we finally got through to him was - off his medications, we wanted to wring his neck. Off his medications, he was angry with everyone because everyone was nagging him or being mean. A videotape would have been useful, I wish we'd had that option. But he finally understood that people were nicer to him when he was medicated, and this wasn't entirely his perception. Because he was not aggressive when medicated, people were less inclined to get angry with him.
After that, we made a point of calling him on it whenever we felt he was unmedicated, so he would realise that WE DID notice, even if he didn't. He needed to know that it made a big difference. Until a kid understands and accepts personal responsibility for taking medications, you will have this struggle. While some kids may simply forget, if a kid is deliberately missing his medications then you have a problem that MUST be addressed.
And I know he's impulsive, and maybe faking the overdose was an impulsive act, but faking taking your medications is not an impulsive act, it's deliberate and premeditated. THAT needs to be addressed. Ask him why, then work on finding a solution to whatever problem he presents. And if there isn't a solution satisfactory to him, then work with whoever you can (medically speaking) to get the message through to him - however inconvenient/unpleasant taking medications may be, it's far worse FOR HIM to not take his medications.
On the subject of medications tasting bitter (or horrible in some other way) - difficult child 1 has got into the habit of taking his medications (which taste very bitter) with neat cordial extract (like Kool-Aid concentrate). If this is a genuine problem, go through as many ideas as possible to find a way of coping. However, I don't think that could be the reason because cheeking it would only make the taste problem worse.
Next, even if you think you've got through to him about being responsible, begin to ensure TIGHT supervision of him to make sure he's actually swallowing his medication. Also keep watch to make sure he doesn't go off somewhere to throw up. Talk to local drug counsellors on what sort of tricks to watch for and how to catch him; also how to make sure the medications are taken. And if he complains at your lack of trust, remind him that his recent behaviour is the reason you've lost trust, and that trust must be earned back. TRUST IS NOT A RIGHT.
Finally, if he ever again pulls a stunt like pretending to take an overdose, then get him to hospital to get his stomach pumped. It's not pleasant, but it is the right course to take for a suspected overdose. Let him live with the consequences of his actions. And if he complains and says you over-reacted, point out that if you had failed to take him to hospital and he HAD taken an overdose, you could have been in legal hot water if you had not covered all bases. Don't make a big song and dance about "I could have lost you," because that's only feeding into the drama he's trying to create. Frankly, this is not about, "Oh dear, he is trying to hurt himself, he must feel terrible," it's far more about getting him away from histrionics and back to practicality and common sense. After the crisis is over, THEN you are more free to discuss any problems he may have about the medications. The right way for him to behave is to tell someone if he has a problem. The wrong way is deceptive and cannot be tolerated or excused for any reason.
How do you react if he falls and gashes his leg? Do you cope, or do you need someone else to step in? Whichever it is, you need to approach this sneakiness over medications in a similar way. Take sensible, commonsense but serious action. Get someone else to take over at that point if you need them to. Always err on the side of caution. It's like living with the boy who cried wolf, only in your case you ALWAYS have to respond even if you're fairly certain it's another false alarm. If he has unpleasant but logical consequences (ie stomach pump; blood tests) every time he "cries wolf", then surely he's going to get the message that this is stupid and irresponsible.
You need to take control back, and not let him keep you on the back foot like this. So from here, you need to make some plans. Work out, either on your own or in conjunction with his doctors/therapists/whoever, exactly what you are going to do in each scenario you have presented here, when it happens again.
For example, write down what you will do if he has apparently taken his medications and yet presents as unmedicated (tell him you have to talk to the doctor about drastically increasing his medications, since they don't seem to be working?)
Then write down what you will do/who you will ring if he apparently takes an overdose.
Keep going with the list, even if you have to put down some fairly unlikely possibilities. Then tuck the list somewhere where you can get at it quickly but of course he can't - never let him see anything like this, it will only give him ideas. You need to seem relaxed, well-prepared, in control.
It's not easy when they're like this - they're cunning as sewer rats sometimes, especially when they turn their little minds towards devious ways to drive us crazy. If you can plan to block off every escape tunnel of his, maybe he'll eventually get the message?
Marg