[Sebastian doesn't comment on the subsequent stitches, at least, so it seems they're acceptable enough.
...Hm.]
There are ways of incapitating a man, or even killing him, which are silent and require very little bodily strength. They do require some knowledge of how the human body works. [Why, Sebastian had to look into a few of them when Ciel started with those "don't wake me up when you're killing people" and "keep one alive for questioning later" demands.]
Sedatives have multiple uses - depending on dosage many of them can relieve pain, or be deadly.