It is important to note that the medicine was all applied after the slime excreted its fluids on the chimera, so the slime's fluids may have had an effect on the drugs being able to work on the chimera despite the low dosage.
Unless the Slime's fluids can somehow multiple the drug then dosage does matter. Usually a multiplication of something like a drug through something else creates a dilution of the original substance, lessening the intended effect, which would worsen the situation and continues to raise the question about dosage.
Chimera's skin itself has never been portrayed as tough in this specific manga, the only indication of the toughness of the chimera's skin was the speartip piercing through the skin.This in itself is an indication and portrayal of the toughness of the Chimera's skin. It's a portrayal of the toughness by way of the speartip
The point made was not about the Chimera's skin being portrayed as super tough in the story, but the assumption made by the author that a Chimera's skin would be as easy to cut as with a scalpel as a human's skin. A Chimera is a fictional fantasy creature of large size. Let's look at how veterinarian surgeons handle, say elephants even in our world. Cutting them open with a scalpel is doable, but difficult with the mass of the elephant. The inner pressure due to the mass would create other problems alone due to the surgeons just slicing the animal open. Instead, they have to perform other methods and have to go through great lengths to ensure their safety and the animal's safety through the procedure. Just like with a human, they're trained to do this, make sure the animal's vitals are ok while performing the procedure. They don't just slice it open with a random scalpel designed to be used on humans. Taking care of animals and humans in a medicinal capacity are two different things. Especially taking care of large animals versus humans. That was the point of that statement. The author assumed that a scalpel designed for a human could be used on a large, fantasy creature, like a Chimera.
Assuming that there was no magic involved, the only magic we have seen from this world is the healing magic shown briefly by the "priest", if a spear can pierce through it, it is more than likely possible that a medical scalpel could as well.
My point, again, was that MC is approaching this world with the assumption that everything will operate the same as in our world. Author is forcing this to be true as Isekai authors almost always do when it comes to the versions of MC's bringing modern ideas to a supposedly middle aged society lacking in "knowledge." Yet, none of this takes into account that this is an alien world and our ways may not work there.
The point about magic is that it exists in this world, whether we've just seen healing so far, it exists. MC is too wrapped up in what he knows and believes to stop and consider that and maybe factor it into his procedures and approach to medicine now that he's in this world.
Well, these are all assumptions as I haven't read the following chapters, but damn at least try and give the author a chance to explain in the following chapters when it's only been 3 chapters in and the current situation hasn't even been resolved.
Calm down. Learn to appreciate criticism for what it is. Also, these stories usually follow along similar tropes. It's obvious the author wants MC to be right all the time despite not having any training or experience as a veterinarian. I could see if MC's first patient in this world was humanoid and shared similar qualities with a human, but even that is sketchy when you're talking about going to an entirely different and alien world. My criticism still stands whether it's first chapter, second chapter, or third chapter. A better author would've considered these worldbuilding aspects. "This is a foreign world to MC, some things that work in our world may not work. Maybe I should make my MC a bit more cautious and observant to how this world works and see what works from his experience in the other world and what he has to adapt to" rather than brute force make everything from MC's world automatically work and be better than what already exists in this world. But like I said, that's one of the tropes of isekai. I'm not surprised.