Why Can’t Kids Just Take Smaller Doses of Adult Meds?

By Adem Lewis / in , , , , , , , , , , , , , , , , , , , , /

Thanks to Brilliant for supporting this episode
of SciShow. Go to Brilliant.org/SciShow to learn how you
can take today’s lessons even deeper with their Physics of the Everyday
course! [♩INTRO] If you’ve ever strolled through a pharmacy
in search of over-the-counter meds, you might have noticed that lots of drugs
have special children’s formulas. And you might think that’s because smaller
people need smaller doses. But you’d be wrong. Because kids aren’t
just tiny adults. In fact, children sometimes need larger doses
of medicine! Welcome to the weird science of allometry. Allometry simply refers to the study of how
physiology changes with size, and it plays a big part in understanding how
much medicine kids should get. You might think bigger bodies would need larger
doses of medicine since they have more of whatever tissue or
cells the drug is targeting. And there are a lot of medications that are prescribed based on a patient’s
weight what’s sometimes referred to as a weight-based
dose. For instance, an adult might be prescribed
five milligrams of medicine for every kilogram they weigh. But what’s really weird is that this dose
isn’t constant throughout a person’s lifetime. You often can’t take the dose per weight
an adult would take and simply multiply it by the child’s weight
to figure out how much they should get. And that’s largely because a person’s
cells use less energy as their body grows. In other words, bigger people have lower mass-specific
metabolic rates than smaller ones. Even at the cellular and subcellular level, oxygen and calorie consumption is just slower
in larger bodies. Not only that, but it’s a nonlinear relationship so as bodies get smaller, metabolism increases
fast. And that matters when it comes to medicines because it impacts how fast your body processes
drugs. Generally speaking, the faster the metabolism,
the faster you break down a drug and that means, even if you’re small, you
might need to take more to have the amount you need stick around long
enough for it to work. Let’s consider acetaminophen, which you
might know as Tylenol. It’s an over the counter drug you can take
to reduce pain and fevers. The regular adult dose for acetaminophen is
650 milligrams. So an adult weighing roughly 80 kilograms the average mass for adults in North America would generally take that amount every four
to six hours as needed. If you’d never heard of allometry, you might
think a child one-quarter that weight, 20 kilograms or so, would get 162.5 milligrams. But that’s way too little. The child will metabolize it super quickly, so the drug won’t really have the chance
to be effective. With junior strength tablets, the recommended
dose is actually 240 milligrams. And for a 44 kilogram child, the recommended
amount is 640 milligrams. That’s basically the same as what’s recommended
for adults, even though the child is about half the weight! And if you calculate the weight-based doses
for everyone, the children actually take about two times
as much. Other drugs can be even more extreme. The adult dose of oseltamivir, which is an antiviral used to treat influenza
infections, is 150 milligrams a day. So, a little under two milligrams per kilogram
per day for our 80 kilogram adult. But pediatric doses range from three to six
milligrams per kilogram per day! As for why metabolic rate scales with mass
in this strange, nonlinear way, well… physiologists don’t know for sure. But by looking at people and animals of all
sizes, they have come up with some good hypotheses! The first and perhaps most obvious is that little bodies belong to individuals that are
still growing, and it takes more energy to build tissues
than to maintain them. So, that’s probably part of it. But there has to be more going on, because the allometric pattern holds across
different sized adults, too. That’s where the shapes of smaller and larger
bodies might be coming into play. Because a smaller body has a larger surface
area relative to its tiny volume, it loses core heat faster. That means it needs to burn more energy and, therefore, run a higher metabolic rate,
to stay warm. But even that still doesn’t fully explain
the allometric scaling of metabolic rate seen in nature, because it only makes sense in so-called “warm
blooded” species like us that strictly regulate their internal temperature
with the heat they produce. And this metabolic rate scaling occurs in
reptiles and other so-called “cold-blooded” species,
as well. There may be another way that overall shape
impacts all this, though, which helps explain that. Some mathematical work suggests metabolic
rates in large animals are limited by their internal plumbing. See, branching blood vessels have to strike
a balance between their width, the pressure of the blood moving against their
walls, and the force it takes to move that blood
around. In a bigger animal with a larger, longer,
and branchier circulatory system, blood flow ends up being slower. Since it’s slower and the body is larger, it takes longer for blood and the oxygen it
carries to get places. And the animal can’t beat its heart faster
or harder to speed things up, because if it tried, its heart would fail. So as an animal grows in size, its cells simply can’t keep using oxygen
at the same rate. More work is needed to sort out how all these
ideas apply to humans specifically. But whatever the reason for children’s elevated
metabolisms, the effect on drug dosing can be pretty dramatic. So, ultimately, it’s not that there are
separate formulations because kids always need less medicine. If anything, it’s so that a patient, or
their caregiver can more carefully adjust the dose they need
for their body size. Liquid medications in particular can be carefully
tailored to a child’s weight. And there are other reasons to have special
formulas for kids, too. Like that pills can be hard to swallow or
even a choking hazard, especially for younger children. So lots of kid’s medicines avoid the issue
by using chewables or liquids instead. Plus, not all medications are recommended
for children of all ages. They might be ineffective or have more severe
side effects in smaller kids. Or they just haven’t been thoroughly tested
yet. The bottom line is, if it isn’t sold in
a separate children’s version, it shouldn’t be given to a child without
consulting a pediatrician. And you should always stick to the children’s
formulations when treating kids because that’s the best way to ensure they
get the right amount even though it may be more than what you’d
take. The allometric scaling of metabolism also
helps explain why we can’t usually give our pets and other
animals weight-adjusted doses of medicine. And it has a really strong impact on what
they eat which you can learn all about in the mammalian
eating portion of Brilliant’s Physics of the Everyday course! While physiology is complicated, all that loss of heat stuff comes from fundamental
physics principles. Which means you can actually learn how to
calculate how much heat differently-sized animals lose, and from that,
how much of their body mass they would need to eat simply to stay warm. And even though you make some entertaining
assumptions, like that animals are spherically shaped,
the theoretical calculation lines up really well with how much biologists
observe animals eating. Which is pretty cool, right? In addition to mammal diets, the course examines
the science behind everything from household items to forensics. So it’s a fun way to learn about your world
and refresh your science knowledge. And right now, the first 200 people to sign
up at Brilliant.org/SciShow will get 20% off the annual Premium subscription. Which is a great deal! So if you’re interested, check it out. And as always, thanks for watching SciShow! [♩OUTRO]

100 thoughts on “Why Can’t Kids Just Take Smaller Doses of Adult Meds?

  1. Go to http://Brilliant.org/SciShow to try their Physics of the Everyday course. The first 200 subscribers get 20% off an annual Premium subscription.

  2. With all the "childproof " medicine containers and their complicated mechanisms, the drugs should be called "Triopenin".

  3. I always find SciShow interesting, but this one I found fascinating. And I love the comments from experts who are adding more to the discussion. (Normally I avoid YouTube comments, but I'm glad I ignored that instinct this time!.)

  4. I wonder if thats also the reason why it’s easier for teens and early 20-something’s to lose weight and why an adult can be deprived of nutrients but still function ok on a raw vegan diet whereas a kid with that kind of diet might literally starve to death.

  5. Oh wow I used get this question all the time when I worked in retail. I can see pediatricians downloading this and playing it for parents

  6. Acetaminophen has been proven to be a placebo and has been proven to be toxic to the liver I disagree with this one I'm shutting it down have a nice day I wouldn't give it to a dog

  7. "The faster the metabolism,the faster you break down a drug". Question: So, wouldn't thyroid issues also be taken into account when calculating doses?

  8. Pain and insomnia are two pretty common health issues, which is why there is no shortage of medication on the market targeting these conditions. However, individual sleep and pain meds and combination drugs like Tylenol PM come with a host of serious side effects that many people are unwilling to take on. Now, a new study points to a cannabis as a very effective treatment for pain and insomnia, potentially replacing sleep medications and even prescription pain medications like opioids.
    The study, which was published in the Journal of Psychoactive Drugs, involved 1,000 people who were taking marijuana legally within the U.S. A full 65 percent of people reported that they were taking cannabis for pain, and four fifths of those in this group said that it was either “very” or “extremely” helpful in addressing their pain.
    In fact, 82 percent of the people in this group said they were able to stop taking over-the-counter pain meds altogether or reduce their usage, while 88 percent said they were able to stop using opioid painkillers.
    Its track record is also impressive when it comes to fighting sleep problems. Nearly three fourths of those interviewed said they bought marijuana to help them sleep, and 84 percent of that group said it helped them. An impressive 83 percent even said that they had reduced or quit taking prescription or OTC sleep aids as a result.

  9. A young woman from Tianmen in China’s Hubei Province recently confessedthat after she contracted the Wuhan coronavirus (CoVid-19) where she lives, staff at the hospital she was sent to barely cared for her and actually tried to murder her.
    This college student, who became something of an internet celebrity after exposing on social media how poorly she was cared for at a Chinese government hospital, spilled the beans before oddly putting up another video not long after urging her followers not to “spread false rumors” online.
    Many believe that this young woman was coerced by the communist Chinese government into retracting her early statements because they made China look bad – this being a common tactic not just in communist China but also here in the United States, where Big Tech is actively censoring all dissenting viewpoints that question official government narratives.
    The young woman, who’s being called “Bomaner” online, says that after she was diagnosed with the Wuhan coronavirus (CoVid-19) following a fever she developed, medical staff at the Tianmen hospital where she was admitted gave her only two pills of Oseltamivir, also known as Tamiflu, every day.
    Instead of arranging for a proper CT scan and blood test, she added, the hospital let her suffer to the point where she became so physically weak that she felt as though she might collapse. She also began to vomit and have loose bowels.
    The same day that Bomaner posted all of this information to her social media accounts, she says police actually went to her parents to inform them that she was spreading “negative information” online about the Wuhan coronavirus (CoVid-19).
    “I was in the hospital’s isolation ward when this happened,” she wrote. “Every word I said on social media was true. I really don’t know which of my statements is considered a wrongdoing. Please come talk to me, instead of talking to my parents.”

  10. As a parent, this is very informative. Also very scary that it’s easy to assume you can just scale a dose based on size…

  11. I really, REALLY hope this doesn't suggest to anyone that they give their children more than the recommended pediatric dose of Tylenol for their children, since Tylenol poisonings are one of the most common pediatric poisonings seen in the emergency room. I wish there'd been a disclaimer or extra warning here, simply because parents accidentally killing or injuring their kids with acetaminophen/Tylenol is already such a national nightmare (more common than opioid poisonings). Never just give your kids adult doses or take more than the recommended doses on the "Drug Facts" section on the packaging of any medication. -Linnea R Boyev, MD PhD

  12. Hey I have a question. Why are Homo Sapiens annual breeder? wouldn't seasonal breeding lead to less pain to females during menstruation? And some other things?

  13. I wonder about anesthesia in particular? I had a bad experience in a dental surgery once where I was crying from pain the whole time, until I heard someone say "this is an adult" (I'm almost 20 but I look around 13) and the general anesthetic finally kicked in a few minutes later. Is anesthesia more dangerous for younger people, regardless of size?

  14. When I was 3 I got super sick and had to go to the hospital. They gave me medicine that’s really only for adults, but they decided to give me half the dose because of my age. Well on the way out of the hospital I said “momma my heart feels funny” and the nurse overheard so they hooked me up to some machines and saw that the medicine is basically about to kill me. They had to flush it from my system and just send me home with no medicine for whatever sickness I had(could’ve been the flu or something I’m not sure it was too long ago for me to remember exactly😂)

  15. i had a real dumbass moment because I wasn’t looking at the screen when I heard him say allometry so I thought he said “a llama tree”

  16. The fact that someone needed a video to explain why a tiny person can’t take as much medicine as a full size person says something… it’s nothing good but it’s something lol

  17. Possibly a silly question. Would an individual trying to build muscle mass or a training athlete need significantly different doses to someone with a sedentary lifestyle?

  18. Does this explain why taking children’s tylonol works better for me than adult pills? Lol. I’ve just assumed it was because it was often on liquid form.

  19. Dumb question here!
    Soo is the kids Tylenol different from the adult? What would happen if an adult takes the kids Tylenol?
    I have an aunt who thinks she's sensitive to medicine so she takes only kids medicine. Nothing would make me happier than to call her out.

  20. Could you please make a corona Virus Video and compare it to the common flu? Or even Spanish flu. Because I’m really getting sick of the media spreading panic without reason.

  21. As a pharmacist who loves the content your channel releases I'm a little disappointed that you didn't mention that the dosing also has to do with how well immature liver and kidneys would handle the drug. For this reason there are many drugs that we don't give at all or give even smaller doses than the weight ratio would suggest. This is a big reason you can't just give adult supplements to children, people think that "natural" supplements are safe, but that's not always the case, your body can't discern what source your getting your potassium from but if you have too high a dose it can have serious cardiac and renal issues. Always ask your doctor or Pharmacist if it's ok to take any sort of medication or supplements no matter your age.

  22. Ever since our boys reached 90+ lbs each, we've been giving them extra strength 500mg Tylenol. The recommended dosage was 480mg from their fluid variant, requiring 5mL (160mg) x 3 dosages.


    And here's where the fun math of saving money comes in shopping at Walgreens in Chicago:

    Children's Tylenol – $7.50 for 120 mL (at 160 mg/5 mL), which would equate to 24 times of 160mg dosage, or $0.00195 per mg, or $0.94 per 480mg dosage.

    TYLENOL Extra Strength – $10.50 for 100 tablets (500 mg), or $0.00021
    per mg, or $0.10 per 480mg dosage.

    So essentially the childrens formula is 9.3 times more expensive than the adult. So if your child can swallow a small pill and weighs in between 72 to 95-lbs, save yourself some money and give them just the 10-cent 500mg Tylenol pills.

  23. In my country, adults are prescribed 500 or 1000 mg of paracetamol per dose, up to 4 times per day, but no more than 3000 mg total over the course of a day. Which is different from the claimed 650 mg up to 4 times per day.

  24. But acetaminophen is a bad example because it isn't done in weight based doses. A 50kg adult and a 200kg adult take the same dose.

  25. I am an adult who takes children's medication. I wonder how that affects people like me. (I can't swallow pills, so for my prescriptions I get them done at a compounding pharmacy but for OTCs like Tylenol and Advil I buy children's.) I haven't really thought about the doses, I just take what I'm told to. My doctors know I take children's but I never thought the formulation would be any different than just liquid.

  26. The Tamiflu dosing is interesting. I'm 4 years in pharmacy and have never seen the child dose that high. Probably because the doctor knows how expensive that would be.

  27. Children's Delsom is a staple for me this time of year. More active ingredient and has sugar in it to make it easier to take. I have a fast medicine metabolism. 800 mg of ibupropin only last 5 hours for me.

  28. Weird! In the U.K. the typical dosage of Paracetamol is 1g (1000mg) or occasionally people may take one, which is 500mg.

  29. So if I make my 10 year old niece drink half of a 250mg of paracetamol for her fever, she's gonna be fine right? I usually keep a stock of paracetamol in the house for my headaches or if I feel feverish, but I also make her and her 8 year old younger brother drink it after I cut it in half for their fevers and headaches.

  30. Off topic question.
    When you can't see you are blind…
    When you can't hear you are deaf…
    When you can't feel you are numb/have cipa (not sure of the spelling on that one)…
    What are you when you can't taste or smell? Can you permanently lose these senses as well?

  31. My aunt used to have horses and a dog. One of the horses and the dog needed to take antibiotics (or some other drug I’m not too sure on what it specifically was) but my aunt had to give more of the pills to the dog than she did to the horse, I’m assuming for the same reasons listed in this video

  32. Why do you say that acetaminophen is known by the brand name Tylenol, but not mention that much of the world know it by the name paracetamol and the brand name Paracet?

  33. I didn't know that. I once took kids paracetamol because I ran out of adult tablets. I was fine but now I know this I won't be doing it again.

  34. Good informative video. And I have to reinforce your statement that children are not just small adults. But I have one niggle and that is with your statement at 4:27 that "the heart of an animal [this includes humans] can't beat faster or harder to speed things up." This is incorrect as any athlete knows. Run around the block, climb several flights of stairs or develop a fever and you will immediately realize the error of your statement. Young children's hearts cannot beat more strongly but their hearts can beat faster in high stress situations or in the face of increased metabolic needs as in the case of infection or anemia. And children can tolerate elevated heart rates for significant periods of time without failing. Adult hearts can and do beat harder (increased stroke volume) as well as faster in those same situations.

  35. Well. This definitely explains why children’s benedryl doesn’t work, but I can’t swallow pills, I need the syrup. But they don’t make adult benedryl syrup. 🤦🏼‍♀️

  36. kids aren't just tiny adults, if you account for the fact that they are drunk tiny adults that is a much better explanation of their entire existence.

  37. well that is an easy question to answer . kids react more intense to all the anti-freeze and other destructive chemicals inside aldult humans meds . so they get poisoned meds with a little less poison in it to not make the parents worry that much . see easiest most truthfull answer ever . you might not like it . but truth is truth even if it stings and hurts . wanna know what is even funnier . no one in their right mind would walk into a maze that has one exit and 8 pitfalls . but when it comes to (ahum life saving meds) everyone just accepts all the side effects because thew can be fixed with new meds that have the same 8 side effects . do meds cure or keep sick ? ask yourself that hard question . and even if the answer to it rips you all from your comfort zones. it is still time to wake up . so FRIKKING wake up, they are killing us and our children and we let them . such good protectors we are . we all earned to burn in hell .

  38. Whenever I have to go to the hospital they ask me how much I weigh. I have to get the hard core pain IV meds cause of my severe arthritis.

  39. When Acetaminophen is illegal in your country…
    (It is known to cause liver failure, sociopathic behavior, some addiction, and even permanent brain damage in unborn babies.)

  40. Wow, I really learned something with this one!

    My family always takes children's medicines no matter how old the person is. I guess it's time to reevaluate!

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