For Clinicians | Pediatric Dosing 101: What Parents Need From You Before They’re Dosing Alone

By Dr. Jamie Wilkey, PharmD, Director of Clinical Education
Medically reviewed and edited by Aaron Asay, PA-C, DMSc, FIBODM, FAWM

Pharmacy school drills one line into you over and over again: children are not small adults. A child’s body absorbs, distributes, and clears a drug on a different timeline than yours does, and the margin around a correct dose is narrower because there’s less child to absorb the error. That’s why every pediatric dose is calculated from weight instead of pulled off a standard adult label.

That’s complicated, but not too hard when a pharmacist or prescriber is just a phone call or message away for parents dosing their kids.  It’s a different problem at 9pm when nobody is reachable and a parent is reading a label written in mg/kg and only knows their child’s weight in pounds.

Today we are going to talk about appropriate medical preparation in children and how to help train parents with pediatric dosing at home. I’ve seen a lot of pediatric dosing errors in my years in practice and I want to help as much as I can to prevent these going forward, especially when information is limited for parents. 

Why children often need more drug per kilogram, not less

The elimination machinery grows up early, and glomerular filtration rate reaches adult levels by 8 to 12 months¹, so by the time a child is 2, the kidneys are clearing drugs roughly the way yours do. What stays different through the grade-school years is body composition and liver metabolism, because a higher share of a child’s weight is water, which spreads water-soluble drugs through a larger relative volume, and phase I metabolism runs above adult rates for some drugs through the first few years¹.

It feels backwards that per kilogram kids often need more than you do rather than less, but a 20 kg child on high-dose amoxicillin for an ear infection takes 1,800 mg a day² while an adult on 875 mg twice daily takes 1,750 mg, which means the 44 pound patient is taking more than the grown-up. That’s not always the case, since I used a high dose example, but it illustrates the point well. Parents round down because it feels safer, and a rounded-down antibiotic course won’t reach therapeutic levels. 

Pediatric dosing is weight-based, and the weight is in kilograms

Every pediatric dose starts from a number the parent usually doesn’t have: their child’s weight in kilograms. Medication doses are written in mg/kg while bathroom scales read pounds, and that conversion is the first place the dose goes wrong. Pounds divided by 2.2 gives kilograms, so a 40 pound child is 18 kg. A parent should be able to run that calculation themselves rather than guessing at it. A tired, sleep-deprived parent doing it at 1am on a phone calculator is introducing risk into the dosing, and they don’t have the clinician spidey sense that goes off when a result comes out too high or too low.

For a family that has a scale but a child who won’t hold still on it, the trick is subtraction: weigh the adult alone, weigh the adult holding the child, and the difference is the child’s weight. When nobody can weigh at all, the current APLS estimates are (age x 2) + 8 kilograms for ages 1 to 5 and (age x 3) + 7 for ages 6 to 12³, though both of them run low, so treat the result as a rough estimate rather than a real answer.

2 places the dose goes wrong after the math is right

If you hand a parent nine doses to measure, 84.4% will get at least one of them wrong, and one in five will be off by more than double on at least one⁴. That was 2,110 parents of children 8 and under, measuring in a study and under observation, with no sick kid howling on their shoulder and none of the sleep deprivation that comes with the real version of that night.

The units are the first of those two places, and here again they confuse parents: the ol’ mL versus teaspoon conundrum. Parents who think in teaspoons reach for a kitchen spoon 30% of the time, while parents who think in milliliters do it 1% of the time⁵, and dosing cups carry more than four times the odds of an error against an oral syringe⁴. Send an oral syringe home whenever you can. I know as a pharmacist I always gave them away for free from behind the counter when patients asked.

Concentration is the second place that errors can be introduced, and it’s the one a good syringe can’t rescue, because a dose in mg/kg gives you milligrams while the bottle is marked in milliliters, and the strength changes from bottle to bottle. Amoxicillin suspension is dispensed at 125, 200, 250, or 400 mg per 5 mL⁶, so the same 5 mL can be three times the dose depending on which bottle came home, and infant ibuprofen drops are double the concentration of the children’s suspension at 40 mg per mL against 20⁷, which matters in any house with a toddler and a second grader keeping both. A volume that worked last time only works again if the strength matches, so have parents read the concentration off the label every time, even on a refill of the same drug.

Accidental double doses to watch out for

Families unintentionally go over the 24-hour maximum in two ways. The first is that acetaminophen turns up inside products that don’t say Tylenol anywhere on the front, so a parent treating a fever with one bottle and a cough with another can give two full doses of the same drug in the same hour without ever seeing it happen. DayQuil and NyQuil Cold & Flu both carry it acetaminophen, as do Theraflu and Mucinex Fast-Max, along with the prescription pain combinations built on it, and ibuprofen hides the same way inside Advil Cold & Sinus and Advil PM.

The second way is simpler: when a parent alternates acetaminophen and ibuprofen through a long night and by midnight it can start to get confusing what went in when. I’ve found that in my own family, writing down the medication, the dose, and the time it was given keeps those long, tired nights clear.

What to send home before they need it

Everything above is executable at 1am only if the parent already has the pieces and basic know-how. Send them home with the child’s weight in kilograms written somewhere they’ll find it, an oral syringe, and the habit of checking the concentration on whatever bottle they’re holding, plus a written drug, dose, prescriber and pharmacy list for any child on daily medication. Parents can also put in Google 25lbs to kg and they can get an answer without having to do math themselves (or use it to double check their own math). Also this is obvious, but worth mentioning that obviously kids are growing, the weight at their physical 9 months ago, might not be accurate anymore! 

All of that assumes there’s something in the cabinet to measure, which is where the real gap sits: a family’s options are a reachable prescriber with an open pharmacy, or nothing, with no sanctioned middle where an age-appropriate formulation is already in the house at a strength that matches the child. Appropriate medical preparation is the name for that middle layer, and it’s what Jase builds for ages 2 through 11, with a licensed provider reviewing every request and writing the prescription. It’s for emergency use only, after first seeking the assistance of a qualified healthcare provider, and it’s in no way a replacement for the pediatrician who knows the child.

The bottom line

Pediatric dosing goes wrong a few ways in the translation and the math. The things parents need to succeed are: the weight in kilograms, an oral syringe, the concentration on the bottle in front of them and what their child’s dose clearly is (for Rx medications). If you’d rather not run it with every family, refer them to us and we’ll do the clinical work on the front end.

Sources

1. Merck Manual Professional Edition. Pharmacokinetics in Children. https://www.merckmanuals.com/professional/pediatrics/principles-of-drug-treatment-in-children/pharmacokinetics-in-children
2. American Academy of Pediatrics. The Diagnosis and Management of Acute Otitis Media. Pediatrics. 2013;131(3):e964. High-dose amoxicillin 80 to 90 mg/kg/day in two divided doses. https://publications.aap.org/pediatrics/article/131/3/e964/30912/The-Diagnosis-and-Management-of-Acute-Otitis-Media
3. Advanced Life Support Group. Advanced Paediatric Life Support: The Practical Approach, 5th edition. Oxford: Blackwell, 2011. Formulas as described in Ali K, Sammy I, Nunes P. Is the APLS formula used to calculate weight-for-age applicable to a Trinidadian population? BMC Emergency Medicine. 2012;12:9. https://pmc.ncbi.nlm.nih.gov/articles/PMC3506443/
4. Yin HS, Parker RM, Sanders LM, et al. Liquid Medication Errors and Dosing Tools: A Randomized Controlled Experiment. Pediatrics. 2016;138(4):e20160357. https://publications.aap.org/pediatrics/article-abstract/138/4/e20160357/52278/
5. Eunice Kennedy Shriver National Institute of Child Health and Human Development. Spoon measurements contribute to many child drug-dosing errors. August 29, 2014. Describing Yin HS et al., Unit of Measurement Used and Parent Medication Dosing Errors, Pediatrics 2014. https://www.nichd.nih.gov/newsroom/releases/082914-podcast-pediatric-med-dosing
6. AMOXIL (amoxicillin) prescribing information. US Food and Drug Administration. Powder for oral suspension 125 mg/5 mL, 200 mg/5 mL, 250 mg/5 mL, 400 mg/5 mL. https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/50542s02950754s01950760s01950761s016lbl.pdf
7. Institute for Safe Medication Practices. Don’t Mix Up Concentrated “Ibuprofen Infant Drops” with “Children’s Ibuprofen.” https://www.consumermedsafety.org/safety-articles/dont-mix-up-concentrated-ibuprofen-infant-drops-with-childrens-ibuprofen