Is there any kind of stress and suffering the Buddhas medicine would not help?

There can be no suffering where there is nobody to suffer and the type of suffering would make no difference.

But until there is nobody to suffer other all sorts of other methods and practices might help, and the method would depend on the type of suffering.

In the long run, though, the only way to end suffering is to end all of it. The 'cessation of suffering' means just that.

Buddha's teaching is on The Mind. And Mind is the creator of all the stress and sufferings (except physical pains and etc.). And once you attain Nivana = The Enlightenment you will no more get any kind of body to feel the physical pains any more.

So simply the answer is Buddha's medicine, which is attaining Nivana, is the one and only treatment to all the stresses and sufferings including physical pains and it covers everything.

Is there any kind of stress and suffering the Buddha's medicine would not help?

Of course not. The ultimate medicine turns everything into emptiness without changing anything.

In the Virecana (Tikicchakka) Sutta (AN10.108):

"Monks, doctors give a purgative for warding off diseases caused by bile, diseases caused by phlegm, diseases caused by the internal wind property. There is a purging there; I don't say that there's not, but it sometimes succeeds and sometimes fails. So I will teach you the noble purgative that always succeeds and never fails, a purgative whereby beings subject to birth are freed from birth; beings subject to aging are freed from aging; beings subject to death are freed from death; beings subject to sorrow, lamentation, pain, distress & despair are freed from sorrow, lamentation, pain, distress & despair. Listen & pay close attention. I will speak."

The Buddha claimed above to be a doctor who treats the disease of suffering of samsara and all its symptoms: birth, death, aging, sorrow, lamentation, pain, distress and despair.

From Kucchivikara-vatthu of the Vinaya, the Buddha taught:

"A nurse endowed with five qualities is fit to tend to the sick: He is competent at mixing medicine; he knows what is amenable or unamenable to the patient's cure, taking away things that are unamenable and bringing things that are amenable; he is motivated by thoughts of good will, not by material gain; he does not get disgusted at cleaning up excrement, urine, saliva, or vomit; and he is competent at instructing, urging, rousing, & encouraging the sick person at the proper occasions with a talk on Dhamma. A nurse endowed with these five qualities is fit to tend to the sick."

He treats the general disease of the suffering of samsara, but not the specific diseases of the body like diabetes or malaria or even neuropsychological diseases.

So, if you need specialized treatment for a specific disease, you should see the doctor who is specialized in that area. The Vinaya quote above implies that the nurse should know how to mix medicines and be competent to treat the disease in question.

In this question, you can see that sometimes apparent psychological disorders actually originate from physical ailments. That's why medical doctors are still needed to treat them. Buddhist teachings do not treat all diseases because that is not their objective.

This answer is also relevant here. In DN16, the Buddha experienced dysentery:

And soon after the Blessed One had eaten the meal provided by Cunda the metalworker, a dire sickness fell upon him, even dysentery, and he suffered sharp and deadly pains. But the Blessed One endured them mindfully, clearly comprehending and unperturbed.

So, although he had attained Nibbana, he could still experience dysentery and all its pains. However, he was unperturbed by it because suffering had indeed ended for him due to him having attained Nibbana. And after his passing away, suffering does not continue in a new life.

So what does this show? The Buddha's cure or medicine of Nibbana ends the suffering of samsara, but it does not end dysentery as a physical disease. For curing dysentery, please see a medical doctor. To cure all suffering permanently through Nibbana, please see the Buddha's teachings (which is same as seeing Dr. Buddha according to Vakkali Sutta).

The medical doctor only treats a temporary disease. If the treatment is successful, you get cured, but you could still get another disease later. But that's the point, for neuropsychological diseases and other medical diseases, you should get treated by a doctor, but to end all suffering permanently, you should seek Buddha's treatment. If you are suffering from severe pains, it's very hard to meditate isn't it? It's easier to get a doctor to treat it first, then you can meditate better.