Tag: drip rate

Categories
Introduction to Nursing Pharmacology Nursing Pharmacology

Dosage Calculation

Dosage Calculations

Dosing Considerations

  • Sex
  • Weight
  • Age
  • Physical condition
  • Other drugs that the patient is taking

Accurate Dosing

  • Dependent on:
    • The prescriber who orders the drug
    • The pharmacist who dispenses the drug
    • The nurse who administers the drug

Measuring Systems

  • Metric system
  • Apothecary system
  • Household system
  • Avoirdupois system

Metric System

  • Solids: gram (g)
    • 1 milligram (mg) = 0.001 g
    • 1 microgram (mcg) = 0.000001 g
    • 1 kilogram (kg) = 1000 g
  • Liquids: liter (L)
    • 1 milliliter (mL) = 0.001 L
    • 1 mL = 1 cubic centimeter = 1 cc

Apothecary System

  • Solids: grain (gr)
    • 60 gr = 1 dram (dr)
    • 8 dr = 1 ounce (oz)
  • Liquids: minim (min)
    • 60 minim = 1 fluidram (f dr)
    • 8 f dr = 1 fluidounce (f oz)

Household System

  • Solids: pound (lb)
    • 1 lb = 16 ounces (oz)
  • Liquids: pint (pt)
    • 2 pt = 1 quart (qt)
    • 4 qt = 1 gallon (gal)
    • 16 oz = 1 pt = 2 cups (c)
    • 32 tablespoons (tbsp) = 1 pt
    • 3 teaspoons (tsp) = 1 tbsp
    • 60 drops (gtt) = 1 tsp

Conversion Table

Commonly Accepted Conversion Between Systems of Measurement
Commonly Accepted Conversion Between Systems of Measurement

Conversion Between Systems

amount of drug available =  amount of drug prescribed
one tablet or capsule #           of tablets or capsules to give

amount of drug available =  amount of drug prescribed
volume available                       volume to administer

Solving for X

amount of drug available =   amount of drug prescribed
one tablet or capsule           # of tablets or capsules to give

10 mg = 40 mg
1                x

Examples

1 oz =   6 oz
30 mL        X

1 oz x X = 6 oz x 30 mL
1(oz)X = 180 (oz) (mL)

X = 180 (oz) (mL)
1 oz
X = 180 mL

Calculating IV Drip Rate

drops/min = mL of solution prescribed per hr x drops delivered per mL
60 min/hr

Difference Between Children and Adults

  • Children absorb, distribute, metabolize, and excrete drugs differently than adults
  • Children’s organs are not as developed as adults’ organs

Pediatric Dosage Calculation

  • Fried’s rule
  • Young’s rule
  • Clark’s rule
  • Surface area calculation

Fried’s Rule

This rule assumes that an adult dose would be appropriate for a child who is 12.5 years (150 months) of age

child’s dose (age <1 year) =   infant’s age (in months)
150 months x average adult dose

Young’s Rule

child’s dose (age 1 to 12 years)  =

child’s age in years
child’s age in years + 12 x average adult dose

Clark’s Rule

Uses the child’s weight to calculate the appropriate dose and assumes the adult dose is based on a 150-lb person

child’s dose  =   weight of child in pounds
150 pounds x average adult dose

Surface Area Calculation

  • Determine the child’s surface area with the use of a nomogram (the height and weight of the child are taken into consideration in this chart)

child’s dose = surface area in square meters
1.73 x average adult dose

Nomogram

Nomogram
Nomogram