This evening Cal developed itchy hives on his face and neck, some kind of allergic reaction to something or other. Joe suggested we give him some children's Benadryl. Having sampled the Benadryl elixir myself a month ago to assure myself that it was not poisoned by the Chinese, I agreed that Benadryl sounded like a reasonable idea, especially close to bedtime as it was. As a Peds resident, I had prescribed Benadryl hundreds and hundreds and hundreds of times, as will know until my dying day that the pediatric dosing is 1mg/kg and that Benadryl elixir comes 12.5mg/5mL. So given that Cal weighs about 30 pounds, I recommended that Joe give Cal one teaspoon, or 5mL, of the Benadryl. It's slightly underdosed, but I'd rather round down than round up.
A few minutes later, Joe comes wandering back in holding the Benadryl bottle.
So maybe we should only give him 3mL.
Well, maybe if you believe in homeopathic dosing of Benadryl, but at that dose, what's the point of giving it at all? It's barely going to do anything. Anyway, it's just a one-time dose.
On the box it says, "for children under six years, ask your doctor."
Honey, I am a doctor, and I am telling you that the dose is 1mg/kg.
But he's under six! The box says!
Please believe me that this is the right dose. It's practically the only piece of information I've retained from my Peds residency. Let me use it.
Actually, that's not entirely true. There is one more piece of dosing information that will forever be burned into my brain. Probably for the rest of my life, even if you wake me up from a dead sleep, I will be able to tell you that the Pediatric dosing of PO Tylenol is 10-15mg/kg, and that the regular strength elixir comes in 160mg/5mL. Old reflexes never really get extinguished.
(Perhaps it would be prudent at this point, upon recommendation from my legal department, to include an addendum. For dosing recommendations for your own child, please consult your real, non-computer health care provider. There are a host of other issues that could possibly affect the dose your child gets outside of their weight, so don't just go by these numbers. But you knew that.)