Drug math lesson 3

Lesson Three

• In this lesson I will introduce the Master Formula

• We will cover every aspect of the Master Formula, and how to use it for drug calculations.

Objectives

• Learn the components of the Master Formula.

• Learn how to decide which components are needed when using the Master Formula.

• Apply all components of drug calculation.

The Master Formula

DD x Wt x SS------------------

C x T

DD = Desired DoseWt = Weight in kgSS = Solution SetC = ConcentrationT = Time

The Master Formula

• Know when to use the entire formula, or just parts.

• The desired dose tells you what parts you will need.– DD = 5mcg/kg over 10min

• Since the DD includes a weight and time portion, you know you will need to use all parts of the Master Formula.

The Master Formula

• What components will you need for the following doses:– DD = 30mg– DD = 30mg/kg– DD = 30mg/kg/min– DD = 30mg/kg over 10min

The Master Formula

• What components will you need for the following doses:– DD = 30mg - DD & C– DD = 30mg/kg– DD = 30mg/kg/min– DD = 30mg/kg over 10min

The Master Formula

• What components will you need for the following doses:– DD = 30mg - DD & C– DD = 30mg/kg - DD, Wt, & C – DD = 30mg/kg/min– DD = 30mg/kg over 10min

The Master Formula

• What components will you need for the following doses:– DD = 30mg - DD & C– DD = 30mg/kg - DD, Wt, & C – DD = 30mg/kg/min - DD, Wt, SS, & C– DD = 30mg/kg over 10min

The Master Formula

• What components will you need for the following doses:

– DD = 30mg - DD & C– DD = 30mg/kg - DD, Wt, & C – DD = 30mg/kg/min - DD, Wt, SS, & C– DD = 30mg/kg over 10min - DD, Wt, SS, C, & T

The Master Formula

• Simplification:– If a variable exists twice, cross it out.

(DD)mcg/kg/min x (Wt)kg x (SS)gtts/ml

(C)mcg/ml x (T)

The Master Formula

• Simplification:– If a variable exists twice, cross it out.

(DD)mcg/kg/min x (Wt)kg x (SS)gtts/ml

(C)mcg/ml x (T)

The Master Formula

• Simplification:– If a variable exists twice, cross it out.

(DD)mcg/kg/min x (Wt)kg x (SS)gtts/ml

(C)mcg/ml x (T)

The Master Formula

• Simplification:– If a variable exists twice, cross it out.

(DD)mcg/kg/min x (Wt)kg x (SS)gtts/ml

(C)mcg/ml x (T)

The Master Formula

• Simplification:– Circle the remaining variables

(DD)mcg/kg/min x (Wt)kg x (SS)gtts/ml

(C)mcg/ml x (T)

The Master Formula

• Simplification:– Rewrite with the remaining variables off to

the side.

(DD) x (Wt) x (SS) gtts/min

(C) x (T)

The Master Formula

• Simplification:– This is how it looks with numbers

5mcg/kg/min x 50kg x 10gtts/ml

1600mcg/ml

The Master Formula

• Simplification:– This is how it looks with numbers

5mcg/kg/min x 50kg x 10gtts/ml

1600mcg/ml

The Master Formula

• Simplification:– This is how it looks with numbers

5mcg/kg/min x 50kg x 10gtts/ml

1600mcg/ml x min

The Master Formula

• Simplification:– This is how it looks with numbers

5 x 50 x 10 gtts/min

1600

The Master Formula

• Simplification:– This is how it looks with numbers

5 x 50 x 10 gtts/min

1600

The Master Formula

• Simplification:– This is how it looks with numbers

5 x 50 x 10 gtts/min

1600

The Master Formula

• Simplification:– This is how it looks with numbers

5 x 5 x 1 gtts/min

16

The Master Formula

• Simplification:– This is how it looks with numbers

25 x 1 gtts/min

16

The Master Formula

• Simplification:– This is how it looks with numbers

25 gtts/min

16

The Master Formula

• Simplification:– This is how it looks with numbers

25 gtts/min

16

25 ÷ 16 = 1.5625

The Master Formula

• Simplification:

about 2gtts/min

The Master Formula

• You are ordered to administer 0.25mg/kg of Cardizam slow IV push, to your patient who has rapid atrial fibrillation.

• You have a patent IV line with a 5cc vial. There is 25mg of Cardizem in the vial.

The Master Formula

• DD = 0.25mg/kg

• C = 25mg/5ml

The Master Formula

• DD = 0.25mg/kg

• C = 25mg/5ml

DD x Wt x SS

------------------

C x T

The Master Formula

• DD = 0.25mg/kg

• C = 25mg/5ml

DD x Wt x SS

------------------

C x T

The Master Formula

• DD = 0.25mg/kg

• C = 25mg/5ml

• Weight = 176 lb

The Master Formula

• DD = 0.25mg/kg

• C = 25mg/5ml

• Weight = 176 lb

176 ÷ 2 = 88

The Master Formula

• DD = 0.25mg/kg

• C = 25mg/5ml

• Weight = 176 lb

176 ÷ 2 = 88 - 8 = 80

The Master Formula

• DD = 0.25mg/kg

• C = 25mg/5ml

• Weight = 176 lb = 80kg

176 ÷ 2 = 88 - 8 = 80

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25mg/kg x 80kg

25mg/5ml

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25mg/kg x 80kg25 mg / 5 ml

÷ 5 ÷5

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25mg/kg x 80kg25 mg / 5 ml

÷ 5 ÷5 5mg / 1ml

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25mg/kg x 80kg5mg/ml

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25mg/kg x 80kg5mg/ml

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25 x 805ml

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25 x 80 ÷ 55ml ÷ 5

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25 x 161ml

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

0.25 x 16ml

0.25 x 16 = 16 ÷ 4 = 4

The Master Formula

• DD = 0.25mg/kg• C = 25mg/5ml• Weight = 176 lb = 80kg

4ml

The Master Formula

• You are ordered to administer Diprivan, 10mcg/kg/min

• You have a 132 lb patient and a 50cc Diprivan bottle with 500mg of drug inside.

• You are to use a minidrip set

The Master Formula

• DD = 10mcg/kg/min

• SS = 60gtts/ml

• C = 500mg/50ml

• Wt = 132 lb

The Master Formula

• DD = 10mcg/kg/min

• SS = 60gtts/ml

• C = 500mg/50ml

• Wt = 132 lb

132 ÷ 2 = 66 - 6 = 60

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10mcg/kg/min x 60 kg x 60gtts/ml

500mg/50ml

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10mcg/kg/min x 60 kg x 60gtts/ml

500mg/50ml

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10mcg/kg/min x 60 kg x 60gtts/ml

500,000mcg/50ml

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10mcg/kg/min x 60 kg x 60gtts/ml

500,000mcg / 50ml

÷ 50 ÷ 50

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10mcg/kg/min x 60 kg x 60gtts/ml

500,000mcg / 50ml

÷ 50 ÷ 50

10,000mcg/ml

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10mcg/kg/min x 60 kg x 60gtts/ml

10,000mcg/ml

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10mcg/kg/min x 60 kg x 60gtts/ml

10,000mcg/ml

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10 x 60 x 60gtts

10,000 x min

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

10 x 60 x 60gtts

10,000 x min

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

1 x 6 x 6 gtts

10 min

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

1 x 6 x 6 = 36 gtts

10 min

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

36 gtts

10 min

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

36 gtts

10 min

36 ÷ 10 = 3.6

The Master Formula

• DD = 10mcg/kg/min• SS = 60gtts/ml• C = 500mg/50ml• Wt = 60kg

about 4gtts/min

The Master Formula

• You are ordered to administer 250ml of fluid over two hours.

• You have a minidrip to use.

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

250ml x 60gtts/ml

120min

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

250ml x 60gtts/ml

120min

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

250 x 60 gtts/min

120

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

250 x 60 gtts/min

120

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

250 x 6 gtts/min

12

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

250 x 6 ÷ 6 gtts/min

12 ÷ 6

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

250 x 1 gtts/min

2

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

125 x 1 gtts/min

1

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

125 x 1 gtts/min

The Master Formula

• DD = 250ml

• SS = 60gtts/ml

• T = 120min

125 gtts/min

The Master Formula

• You have been ordered to administer 150mg of Amiodarone in a 100cc bag of D5W over 10 minutes for a patient with stable runs of ventricular tachycardia.

• You have a 10gtts/ml solution set.

The Master Formula

• DD = 150mg• SS = 10gtts/ml• C = 150mg/100ml

• T = 10min

The Master Formula

• DD = 150mg• SS = 10gtts/ml• C = 150mg/100ml

• T = 10min

150mg x 10gtts/ml

150mg/100ml x 10min

The Master Formula

• DD = 150mg• SS = 10gtts/ml• C = 150mg/100ml

• T = 10min

150mg x 10gtts/ml

1.5mg/ml x 10min

The Master Formula

• DD = 150mg• SS = 10gtts/ml• C = 150mg/100ml

• T = 10min

150 x 10 gtts/min

1.5 x 10

The Master Formula

• DD = 150mg• SS = 10gtts/ml• C = 150mg/100ml

• T = 10min

150 x 1 gtts/min

1.5 x 1

The Master Formula

• DD = 150mg• SS = 10gtts/ml• C = 150mg/100ml

• T = 10min

150 gtts/min

1.5

The Master Formula

• DD = 150mg• SS = 10gtts/ml• C = 150mg/100ml

• T = 10min

100 gtts/min

Lesson Three

• This is the conclusion of lesson 3.

• Put everything you have learned together, and practice multiple drug calculations.