chapter 6 calculation of oral medications─solid and liquids

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

Chapter 6 Calculation of Oral

Medications─Solid and Liquids


Dosage Calculations• D = Desired dose or order• H = On hand or have• S = Supply


Three Methods of Dosage Calculation• Proportion expressed as two fractions• Proportion expressed as two ratios• Formula method


Proportion Expressed as Two Fractions• SUPPLY = X

HAVE DESIRE


Proportion Expressed as Two Ratios• SUPPLY : HAVE :: X : DESIRE


Formula Method• DESIRE × SUPPLY = X

HAVE


Clearing Decimals• When the numerator and denominator in Desire/Have are

decimals, add zeros to make the number of decimal places the same

• Then drop the decimal points• Operation replaces long division


Important to Remember• Before solving problems, check to be certain the order

and supply are in the measure• If not in same measure, must convert one or the other to

its equivalent


Question

The client is to receive acetaminophen 975 mg po every 6 hours prn for an earache. How many tablets would the nurse administer?A. 2B. 3C. 4D. 5


Answer

B. 3• Desire/Have × Supply = X is the formula method.

Supply : Have :: X : Desire is the proportion expressed as two ratio method. Supply/Have = X/Desire is the proportion expressed as two fraction method

• 975 mg/325 mg × tablet = 3 tablets is the formula method. tablet : 325 mg :: 3 tablets : 975 mg is the proportion expressed as two ratio method. tablet/325 mg = 3 tablets/975 mg is the proportion expressed as two fraction method


Question

The client is to receive Mycostatin oral suspension 200,000 units po twice a day. The available Mycostatin oral suspension is 100,000 units per mL. How many milliliters of medication would the nurse administer?A. 1B. 2C. 3D. 4


Answer• B. 2

– Desire/Have × Supply = X is the formula method. Supply : Have :: X : Desire is the proportion expressed as two ratio method. Supply/Have = X/Desire is the proportion expressed as two fraction method

– 200,000 units/100,000 units × milliliter = 2 milliliters is the formula method. milliliter : 100,000 units :: 2 milliliters : 200,000 units is the proportion expressed as two ratio method. milliliter/100,000 units = 2 milliliters/200,000 units is the proportion expressed as two fraction method


Proficiency With Drug Calculations• Practice = Success

chapter 6 calculation of oral medications─solid and liquids

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