If the patient clearly stated he does not want an antipsychotic and you still give one without informing the patient, you are deceiving them.
Now some may argue that if the patient didn't have capacity to begin with, this is one of those things where you can fudge.
Without getting into that area, I would not recommend giving the Seroquel because it is deception. If the patient is smart enough to figure that Abilify is an antipsychotic, they will likely found out that Seroquel is an antipsychotic too. In which case they will be very very ticked off with you and the physician-patient relationship may be permanently damaged. Remember, a doctor is not supposed to practice paternalism. We are not supposed to do something for the patient's good without their consent unless they lack capacity or meet commitment critieria. Even then we must do everything we can to have them on board as much as possible.
To answer your question, legally and ethically misguiding the patient would be wrong. Practically speaking, it would only be easier at first. When the patient figures out you decieved them, practically, it will make things far worse than being honest with them in the first place.
If you want to, you could mention several things that may quell the patient's concerns. E.g. that several medications have multiple effects and that Seroquel does not have any antipsychotic benefit at the lower dosages.
I don't know the specifics of the case but from anectdotal experience, I've seen several patients seemingly antidepressant resistant but it turned out the doctor wasn't doing it right to begin with.
E.g. the person is tried on Prozac 20 mg x 1 week, then Citalopram 20 mg x 1 week, the Zoloft 50 mg x 1 week....on and on and on and no benefit.
I'm probably telling you something you already know. With antidepressant treatment, use the data brought forth by the STAR*D trial.
Increase antidepressants as recommended by the manufacturer until they reach the maximum dose or until the patient cannot tolerate a higher dosage. Stay on that dosage for at least 4-6 weeks (I tend to do 4 weeks. I've never seen a patient that got a benefit at 6 weeks that didn't get it at 4). The patient must have been compliant during that time.
Remember, antidepressants only provide a benefit 55-70% of the time across several studies for all antidepressants at the maximum dose. When I say "a benefit" that is literal. The majority don't get improvement to where they want and need it. That benefit may be minimal. Higher dosages do yield higher efficacy. For that reason, don't be shy to increase the dose if the patient is not getting any benefit or full remission so long as it's in the manufacturer's guidelines.
Now all this said, I've seen very few doctors use STAR*D data. I've seen too many patients fall in the trap I mentioned ("I've been on Prozac 20 mg for one year and it doesn't work!"). I often write tapering up scheduled prescriptions where the patient will only get the minimal dosage for a week, then will get the next higher dosage. IMHO there is no excuse to not increase the dosage if the patient has been on the medication for 6 weeks, they still suffer from excessive depression and anxiety, with no further improvement and they are not on the maximum dosage as defined by the manufacturer or by medication tolerance.
If there's partial response or no benefit at the maximum dosage (defined by the manufacturer or by medication tolerance), add an augmentation agent or try another antidepressant. Only go above the maximum if you can find some data supporting that it's safe (and there are plenty of studies showing that at even higher dosages recommended by the manufacturer there's better response and it's safe. If you find the study, copy it and put it in the patient's chart and explain to the patient your thoughts so they understand). I only do this if the person has a benefit from the med but it's been at the maximum dosage for 6 weeks and the person needs more improvement. I pretty much never go over the max if the person had no benefit whatsoever at the max. That suggests to me that this medication probably doesn't work at all on this person based on the receptor fit theory.
Also consider over the maximum dosage if the person is obese. Remember, the maximum dosage is based on data for people based on a pool of data that is not specific for obese people. If the person is obese, adjust the dosage based on their weight. Don't just increase it blindly.
Consider differing mechanisms (E.g. a SNRI, Wellbutrin, Trazodone, etc) if 2 or more SSRI trials have failed.
Also remember that several augmentation strategies are very cheap and effective. Lamictal, Buspirone, T3, and Wellbutrin are all available in generic and have STAR*D data. Several of the newer augmentation agents such as Abilify or Seroquel have relatively more side effects, are expensive, and are being overprescribed IMHO. (Buspirone at $4 a month with little side effects vs Abilify that's hundreds a month and requires labwork!?!?!?!, and there's no data clearly showing superiority with Abilify? Why are so many doctors then giving out Abilify? It's called drug reps and laziness.)
Also remember Fish oil while having questionable benefits in treating mental illness on it's own has decent data backing it as an antidepressant augmetation agent. It's cheap and readily available and good for health anyway. IMHO a better first choice than Abilify or Seroquel. I recommend that all of my adult patients take fish oil unless they are vegetarian. If it provides no psychiatric benefit it will provide health benefits.
Consider if the psychosocial component is justifiably keeping the person depressed. There are a class of patients that IMHO get maximum medical benefit but their depression is psychosocial and the biological component can not be further improved.
And always consider that if a patient is not getting better, did you check the thyroid labs? I occasionally see a patient that's been depressed for years, was treatment resistant and the so-called medical doctor never ordered a thyroid lab.
