You definitely won't find more than 100mg/ml from a vial! 100mg/ml is the ideal concentration for IM injection (used commonly for conscious sedation in children to avoid the discomfort of IV access), with doses of 300mg IM not uncommon for an average 8 year-old.
50mg/ml is the maximum recommended concentration for IV bolus, as high doses pushed rapidly occasionally cause people to briefly stop breathing, and a more concentrated solution hits harder and faster. That said, we're talking 300mg IV here, waaaaay beyond recreational dosages! You can push sub-anaesthetic doses fast without issue, I see doctors regularly smash patients with 90mg IV, followed by Fentanyl AND Roccuronium (or sometimes Midazolam), and FAST, one after the other to intubate the patient. Not that the patient breathes after the Rocc, but that's intentional! There's a very small chance of laryngospasm and apnoea, but it's very rare.
They tend to go for higher concentrations in vials because that means you can IM it, and just dilute it down with 0.9% saline if needed for IV.
Two big points to note if you're making up your own liquid to IM/IV:
When pharmaceutical liquid is evaporated, the powder that results is rarely 100% pure by weight, as it contains various additives/preservatives and some salt to make the solution the same osmolarity as body tissues and blood. 5ml of 50mg/ml solution sometimes gives you 300mg of powder instead of the expected 250, but at least it has nothing nasty in it!
It should only be made up using sterile water, not 0.9% sodium chloride! If the powder came from a vial, it will still contain the salt, and will give you a decent osmolarity at between 100mg/ml and 50mg/ml (i.e 300). If not, pure Ketamine HCl gives a roughly ideal osmolarity between the same concentrations in water. 200mg/ml is going to be hypertonic, but not excessively so. Your biggest issue will be keeping the stuff in solution... you'll end up with a lovely chunky crystal in your vial if you let it get cold!
It's almost more of an issue getting osmolarity right with IM administration, since the liquid stays in contact with the muscle tissue for a period of time, possibly causing damage. How much, I'm not sure! IV wise, it's little issue... 2ml of hyper/hypotonic solution won't matter much when diluted down by the other 5 litres of blood in your body!
Might do a visual tutorial for making liquid to IM, can't say I've seen anything beyond text descriptions!
