It’s probably because the variation in organ size is the most important issue, and in adults there is much less variation than there would be, say, between a one-month old and a nine-year old. Also, to some extent, the maturation of enzymes that metabolize drugs must be taken into account.
Naloxone is an opioid antagonist and is used in the treatment of opioid addiction. It can be given intravenously (very fast action), subcutaneously, or intramuscularly. It is not formulated for intranasal use! It may be OK, but the dosage would be unknown; and there may be added stabilizers that are harmful in the nose. NOT recommended.
I don’t know exactly what you mean by “intense.” If it’s recommended by a medical doctor it is probably safe, as there are strict prescribing deadlines. If you mean overdosing, that is by definition never safe. Don’t experiment with drugs!
That’s the result of testing so far. Remember, for each herbal you’ve heard of that may work, there are hundreds in use in traditional pharmacy that are useless or dangerous (including many, like rhinoceros horn as an aphrodisiac, harmful to endangered species).
About 30 different compounds; many more than that brands and mixtures, prescription and OTC, brand name and generic.