Pediatric Dose Calculator

Pediatric dose calculation determines the appropriate medication dosage for children based on their weight (mg/kg). Unlike fixed adult dosing, pediatric doses are weight-based to account for differences in body size and metabolism.

Pediatric dose is calculated as: Dose = Weight (kg) × Dose per kg (mg/kg). For example, if a child weighs 20 kg and the prescribed dose is 5 mg/kg, the single dose is 100 mg.

A single dose is the amount given at one administration. Daily dose = single dose × number of doses per day (derived from frequency). For example, if a single dose is 100 mg q6h, the daily dose is 400 mg.

Children have different body surface area, metabolic rates, and organ function compared to adults. Weight-based dosing ensures the drug concentration in the blood is within the therapeutic range regardless of the child size.

The maximum single dose is the highest amount that can be safely given at one time, often capped at the adult dose. For example, acetaminophen has a max single dose of 15 mg/kg, not to exceed 650–1000 mg per dose in adults.

The maximum daily dose is the total amount of medication allowed in a 24-hour period. Exceeding this can lead to toxicity. For example, acetaminophen max daily dose is 75 mg/kg/day, not to exceed 4 grams in adults.

Frequency indicates how often a dose should be administered. q4h = every 4 hours (6 doses/day), q6h = every 6 hours (4 doses/day), q8h = every 8 hours (3 doses/day), q12h = every 12 hours (2 doses/day).

Doses per day = 24 / hours between doses. q4h = 6 doses/day, q6h = 4 doses/day, q8h = 3 doses/day, q12h = 2 doses/day, q24h = 1 dose/day.

Exceeding the maximum daily dose increases the risk of adverse effects and toxicity. For acetaminophen, exceeding 4 g/day can cause hepatotoxicity. For ibuprofen, exceeding 2.4 g/day increases GI bleeding risk.

No. Neonates (0–28 days), infants (1–12 months), children (1–12 years), and adolescents (12–18 years) have different dosing considerations due to changes in liver enzymes, renal function, and body composition.

Body surface area (BSA) dosing is an alternative to weight-based dosing, often used for chemotherapy drugs. Dose = BSA (m²) × Dose per m². BSA is calculated using formulas like Mosteller: √(height(cm) × weight(kg)/3600).

BSA-based dosing is preferred for chemotherapy, certain antivirals, and drugs with a narrow therapeutic index where more precise dosing is required. Most pediatric drugs use weight-based dosing.

Liquid formulations include syrups, suspensions, and solutions that allow flexible dosing based on weight. Common concentrations: acetaminophen 160 mg/5 mL, ibuprofen 100 mg/5 mL, amoxicillin 250 mg/5 mL.

To convert: Volume (mL) = Dose (mg) / Concentration (mg/mL). If the prescribed dose is 200 mg and the concentration is 100 mg/5 mL (20 mg/mL), then volume = 200/20 = 10 mL.

The rule of 6 is an old method for calculating dopamine and other vasoactive drug infusions: 6 × weight (kg) = mg added to make 100 mL solution, where 1 mL/hr = 1 mcg/kg/min. It has largely been replaced by standard concentration protocols.

Infusion rate (mL/hr) = Total volume (mL) / Time (hr). For weight-based infusions: Dose rate (mcg/kg/min) = (Infusion rate × Concentration) / (Weight × 60).

The maximum acetaminophen dose for children is 75 mg/kg/day, not to exceed 4 g/day in adults. For infants under 3 months, consult a pediatrician. Single dose should not exceed 15 mg/kg.

Maximum ibuprofen dose is 40 mg/kg/day, divided q6–8h. Single dose is 5–10 mg/kg. For OTC use, do not exceed 10 mg/kg per dose. Not recommended for infants under 6 months.

Antibiotics often have wider therapeutic ranges and may use higher mg/kg doses. They also require consistent dosing intervals to maintain therapeutic blood levels. Analgesics are often dosed PRN (as needed) with stricter max daily limits.

TDM measures drug concentrations in blood to ensure levels are in the therapeutic range. Commonly monitored drugs include vancomycin, gentamicin, phenytoin, and digoxin. Dosing adjustments are made based on levels.

Children with impaired renal function may require dose adjustments because many drugs are renally excreted. Dosing intervals may need to be extended or doses reduced to prevent accumulation and toxicity.

Drugs metabolized by the liver (e.g., acetaminophen, phenytoin) may require dose reduction in hepatic impairment. Monitoring liver enzymes is important when using hepatically cleared medications.

NTI drugs have a small window between therapeutic and toxic levels. Examples include digoxin, lithium, warfarin, phenytoin, theophylline. These require careful dosing, TDM, and frequent assessment.

A loading dose is a higher initial dose given to quickly achieve therapeutic drug levels. It is calculated as: Loading dose = Desired concentration × Volume of distribution / Bioavailability.

A maintenance dose is the regular dose given to keep drug levels in the therapeutic range. It is calculated based on clearance and desired steady-state concentration.

There is no simple conversion as it depends on the child height and weight. Use BSA formulas (Mosteller, Du Bois) to calculate BSA in m², then multiply by the mg/m² dose.

The safety margin is the ratio between the toxic dose and the therapeutic dose. Drugs with a wide safety margin (e.g., amoxicillin) can tolerate dosing errors better than NTI drugs.

Always double-check: (1) Verify weight in kg, (2) Confirm dose per kg from reliable source, (3) Calculate single and daily dose, (4) Compare with max dose, (5) Recheck calculations independently.

Common errors include using pounds instead of kg, incorrect decimal placement, confusing mg and mL, miscalculating frequency, exceeding max daily dose, and using adult formulations/doses.

Weight is the foundation of all pediatric dose calculations. A 10 kg error can result in a dose that is double or half the intended amount, potentially causing toxicity or therapeutic failure.