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Drug Calculate, Medicine Calculations

How to Calculate Pediatric Drug Doses

Children requires small doses of medicine, which is calculated as per their body weight (mg/kg) or body surface area (BSA)(mg/m2). We can calculate the body weight of the baby in pounds to kilograms (1 kg= 2.2 lb). Doses are always calculated in mg/kg/day or mg/kg/dose.

Doses can be changed as per the injections which are used to the small babies and also take care of the doses as per medicine. Selected drug formulas and selected drug calculations are given below….

Calculation of Drops Per Minute


Total Volume (in ml)    X    Drop Factor/ml

Total Infusion Time (in minutes)

Calculation of Drug Dosages


Dose of Drug Required    X    Volume Available

Strength of Drug Available

i.e.,   A=D /HXQ

Calculation of Doses in Mg/Hour

(When wishing to calculate infusion rate in ml/hr.)


Mg/Hour Required    X     Total Volume (ml)

Total Strength (mg)

Calculation of Doses in Micro grams / Minute

(When wishing to calculate how many ml/hr. to infuse)


Microgram/min     X   60 min /hour    X    Total Volume (ml)

Total Strength of Medication (micrograms)

Calculation of Ml Per Hour

(When using an infusion pump to deliver I.V. fluids)


Total Volume to be Infused (in ml)

Total Infusion Time (in hours)

Inj. Dopamine Drip


  • 30 mg Kg of Inj. Dopamine add in 5% dextrose to make total of 50 ml
  • 1ml/hour = 10 mcg/kg/minute

 Indications – Hypotension

Side Effects

  • Arrhythmias
  • Tachycardia
  • Vasoconstriction
  • Hypotension
  • Widened QRS Complex
  • Bradycardia, Hypertension
  • Increased Pulmonary Artery Pressure
  • Excessive Diuresis.


  • HGT less than 40mg/dl
  • Give 10% dextrose 4 ml/kg I.V. push.

Inj. Adrenaline


  • 0.1 – 0.3ml/kg of 1:10,000 concentration
  • (1ml Inj. Adrenaline add 9 ml Normal Saline /Sterile Water to make total 10ml)


  • Severe Bradycardia
  • Hypotension

Side effects

  • Ventricular Arrhythmias
  • Tachycardia
  • Pallor
  • Tremor
  • Severe Hypertension
  • Hypokalemia

Inj. Atropine


  • 0.01 to 0.03 mg/kg/dose
  • Inj atropine 1ml add 5 ml Normal Saline /Sterile Water to make total 6ml 0.1ml= 0.01mg


  • Bradycardia

Side effect

  • Tachycardia
  • Mydriasis
  • Urinary Retension
  • Fever
  • Esophageal Reflux.

Inj. Midazolam


  • 0.1mg/kg=0.1ml/kg


  • Sedation
  • Convulsion

Side effects

  • Sedation
  • Respiratory Arrest
  • Apnea
  • Hypotension