170 likes | 297 Views
This chapter delves into calculating drug doses using different systems of measurement, including metric units such as meters, liters, and grams, as well as the International System of Units. It provides detailed methodologies for calculating doses from prepared-strength liquids, tablets, and capsules, using proportions and dosage schedules. The guide includes examples of percentage-strength solutions and detailed calculations for intravenous infusion rates, ensuring healthcare professionals can accurately determine the required medication dosage and infusion rates for patient care.
E N D
Chapter 4 Calculating Drug Doses
Systems of Measure • The metric system • Meter, liter, gram • The International System of Units • Meter, kilogram, second • Drops as units of volume • Standard: 16 drops (gtts) = 1 ml • Household units of measure • Teaspoon, tablespoon, cup
Calculating Doses From Prepared-Strength Liquids, Tablets, and Capsules • Calculating with proportions • Drug amounts in units • Calculations with a dosage schedule
Calculating with Proportions • Convert to consistent units of measure • Set up a straightforward proportion: Original Dose = Desired Dose Per Amount Per Amount
Drug Amounts in Units Original Dose = Desired Dose Amount Amount
Calculations with a Dosage Schedule • Calculate the dose needed • mg/kg • Calculate the amount of the preparation: Original Dose = Desired Dose Per Amount Per Amount
Calculating Doses From Percentage-strength Solutions • Types of percentage preparations • Weight to weight • Weight to volume • Volume to volume
Calculating Doses From Percentage-strength Solutions • Solutions by ratio • Ratio by grams to milliliters • Ratio by simple parts • Solving percentage-strength solution problems • Three equations
Solving Percentage-strength Solution Problems (Equation 1) % Strength = Solute Total Amount --Percent strength is in decimals --Solute is in grams or cubic centimeters --Total amount = (solute + solvent)
Solving Percentage-strength Solution Problems (Equation 2) Amount of Solute = Amount of Solute Total Amount 100 Parts --100 parts = grams or cubic centimeters
Solving Percentage-strength Solution Problems (Equation 3) % Strength= (Dilute Solute)x(% Strength of Solute) Total Amount --Percentage strength is in decimals --Total amount = solution
Calculating DosesFrom Percentage-strength Solutions • Diluents and drug doses • Amount of diluent affects only the amount of time required to administer the drug; amount of active drug is the same
Calculating Intravenous Infusion Rates • Total solution over time • Amount of drug per unit of time
Calculating Intravenous Infusion Rates • Total solution over time: Flow Rate (ml/min) = Total Solution (ml) Time (min)
Calculating Intravenous Infusion Rates • Amount of drug per unit of time (Equation 5): Concentration (amount/ml) = Total Drug Amount Total Solution (ml)
Calculating Intravenous Infusion Rates • Amount of drug per unit of time (Equation 6): Flow Rate (ml/min) = Amount x Milliliter Minute Amount
Calculating Intravenous Infusion Rates • Amount of drug per unit of time (Equation 7): Flow Rate (drops/min) = Amount×Milliliters×Drops Minute Amount Milliliter