Every time you read the back of a medicine box the age is always 12 when you are considered an adult. Why is this?
In: Biology
It’s because the development of drug metabolism and clearance pathways (basically, the chemical reactions inside the body) begins in the fetus and throughout childhood.
By the time they reach adolescence, they are assumed to have developed these pathways fully, so they can now metabolize drugs the same way as it happens in adults.
(But just to tell you, body weight or body surface area is more used in pediatrics than age.)
Children have underdeveloped immune systems, at around 11 years old the metabolism of the body begins to change in preparation for/as part of puberty. So children 12 and older have a better way to regulate body temperatures, develop specific immunities, and process toxins, all of which make it so that they are closer to adults and can take medicine differently.
To be an adult in the eyes of how medicine is dosed, is based on weight. For most drugs, you become an adult at 100 lbs or 45kg. The average weight generally reaches that amount at 12. Children use weight based dosing and adults have fixed dosing. Once you are beyond a certain size, you can use standardized dosing, however, that can break down in the obese.
Follow up, why did I used to get fevers every time I was sick with any kind of minor cold when I was younger, but ever since I was 18-19 (can’t remember exactly when it changed), I only get fevers for the most severe of infections?
12 isn’t a “magic number”. This is most likely the age where a chosen percentile (say 95th percentile ie. 95% of people of that age) can safely take the recommended adult dose. This will have been determined during the testing stage.
There will be outliers though who cannot safely take the stated dose at that age. Those who are severely underweight for example. Or those who are particularly sensitive to certain drugs.
The inverse is also true. Some well developed younger persons can safely take an adult dose. Children are often given higher doses of paracetamol in medical care settings than recommended by manufacturers. In these cases the dose may be determined by their bodyweight.
It is mostly to do with body mass and a little to do with liver and kidney function.
By the time folks are 12, most people’s liver and kidneys are well developed and their body mass is decent enough to handle many medicines.
The other responses point out that children and adults are different and have different body sizes, but the question is why do all medicines use the age of 12, instead of some using 13 or 14?
The answer must have something to do with the FDA drug approval process. There must be some regulatory reason that “12 years and over” and “children under 12” are the phrases that are always used.
in addition to body mass and more “adult” reactions to things: by that age most kids are grown enough that they can be intubated normally if there is an adverse reaction and they can do a better job of describing the symptoms of side effects
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