PEDIATRIC DOSAGE CALCULATIONS JENNIFER KEAN MSN RN CCRN

PEDIATRIC DOSAGE CALCULATIONS JENNIFER KEAN MSN, RN, CCRN

DOSING • MOST DRUGS FOR CHILDREN ARE DOSED ACCORDING TO BODY WEIGHT (MG/KG) OR BODY SURFACE AREA (BSA) • CARE MUST BE TAKEN TO CONVERT BODY WEIGHT FROM POUNDS TO KILOGRAMS BEFORE CALCULATING DOSES BASED ON BODY WEIGHT • 1 KG = 2. 2 LBS • DOSES ARE OFTEN EXPRESSED AS MG/KG/DAY OR MG/KG/DOSE • IF PROVIDER WRITES MG/KG/D, YOU MUST CLARIFY; IT IS A CONFUSING ORDER • DOSING ALSO VARIES BY INDICATION, SO DIAGNOSTIC INFORMATION IS HELPFUL • MOST INSTITUTIONS HAVE POLICIES THAT REQUIRE 2 NURSES TO CHECK ANY DOSES OR CALCULATIONS

EXAMPLE 1 • CALCULATE THE DOSE OF AMOXICILLIN SUSPENSION IN MILLILITERS FOR A 1 YEAR-OLD CHILD WEIGHING 22 LB. • THE DOSE REQUIRED IS 40 MG/KG/DAY DIVIDED TWICE DAILY (BID) • THE SUSPENSION COMES IN A CONCENTRATION OF 400 MG/5 ML

STEP 1 • CONVERT POUNDS TO KILOGRAMS 22 LB = _____ KG

ANSWER 22 LB = 10 KG

STEP 2 • CALCULATE THE DOSE IN MILLIGRAMS 40 MGX 10 KG = _______ MG/DAY

ANSWER 40 MG X 10 KG = 400 MG/DAY

STEP 3 • DIVIDE DOSE IN HALF (GIVEN BID) 400 MG / 2 DOSES = ______ MG / DOSE

ANSWER 400 MG / 2 DOSES = 200 MG / DOSE

STEP 4 • CONVERT THE MILLIGRAM DOSE TO MILLILITERS 200 MG / DOSE / 400 MG/ 5 ML = _____ ML

ANSWER 200 MG / 400 MG _______ BID X ML 5 ML = ______ ML

ANSWER • SINCE YOU ARE DIVIDING 2 FRACTIONS, YOU MUST FLIP THE SECOND FRACTION 200 MG 5 ML X X ML = _______ ML BID 400 MG

THE ANSWER IS 2. 5 ML BID ALWAYS MAKE SURE YOUR ANSWER MAKES SENSE. THIS SOUNDS RIGHT FOR A 1 -YEAR-OLD CHILD.

EXAMPLE 2 • CALCULATE THE DOSE OF CEFTRIAXONE IN MILLILITERS FOR MENINGITIS FOR A 5 -YEAR-OLD CHILD WEIGHING 20 KG. • THE DOSE REQUIRED IS 100 MG/KG/DAY GIVEN IV ONCE DAILY • THE DRUG COMES PREDILUTED IN A CONCENTRATION OF 500 MG/ML

STEP 1 • CALCULATE THE DOSE IN MILLIGRAMS 100 MG X 20 KG = _____ MG / DAY

ANSWER 100 MG X 20 KG = 2000 MG/DAY

STEP 2 • DIVIDE THE DOSE BY THE FREQUENCY 2000 MG/DAY / 1 (DAILY) = 2000 MG/ DOSE

STEP 3 • CONVERT THE MILLIGRAM DOSE TO ML 2000 MG / 500 MG/ML = ______ ML/ DOSE X 1 DAILY 4 ML ONCE DAILY

PROBLEM 1 • ORDER: AMOXICILLIN (AMOXIL) 60 MG PO TID CHILD’S WEIGHT: 12. 5 LB. DRUG CONCENTRATION: 125 MG/5 ML

FORMULA D X H V=

PROBLEM 2 • ORDER: AMPICILLIN 350 MG IM Q 6 H • CHILD’S WEIGHT AND AGE: 61. 5 LB AND 9 YEARS OLD • DRUG CONCENTRATION: 500 MG/2 ML

FORMULA D X H V

DOSAGE PER BODY SURFACE AREA • THE FOLLOWING INFORMATION IS NEEDED TO CALCULATE THE DOSAGE: • ORDER WITH NAME OF DRUG, DOSAGE, AND TIME FRAME /FREQUENCY • CHILD’S HEIGHT, WEIGHT IN KG, AND AGE • INFORMATION ON HOW DRUG IS SUPPLIED • PEDIATRIC DOSAGE (AS LISTED BY MANUFACTURER OR HOSPITAL FORMULARY) • CHILD’S BSA

CALCULATING THE DOSE • MULTIPLY THE BSA BY THE MINIMUM AND MAXIMUM DOSE (SUBSTITUTE BSA FOR WEIGHT) • IS THIS A SAFE DOSE? • CALCULATE DRUG DOSE USING D/H OR BY RATIO/PROPORTION

PROBLEM 3 • CHILD WITH RHEUMATIC FEVER; 45 LB, 4 YEARS OLD • ORDER: PENICILLIN V POTASSIUM 250 MG PO Q 8 H • PEDIATRIC DOSE: 25 -50 MG/KG/DAY • DRUG CONCENTRATION: 125 MG/ 5 ML

PROBLEM 4 • CHILD WITH SEIZURES; 7. 2 KG, 9 MONTHS OLD • ORDER: PHENOBARBITAL 25 MG PO TID • PEDIATRIC DOSE: 5 -7 MG/KG/DAY • DRUG CONCENTRATION: 20 MG/5 ML

PROBLEM 5 • CHILD WITH LOWER RESP. TRACT INFECTION; 17 LB, 6 MONTHS OLD • ORDER: CEFPROZIL (CEFZIL), 100 MG PO Q 12 H • PEDIATRIC DOSE: (> 6 MONTHS) 15 MG/KG/12 H