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Calculations (updated 2/19)

Calculations (updated 2/19) . Calculating Amount Needed. Tablets for suspension Percentage preparations Aliquots Alligation Solubility Specific gravity Capsule packing. Will go over in PPC. Equivalent Measurements. Tsp = 5 mL Tbsp = 15 ml 1 fl oz ~ 30 mL 1 pint = 473 mL

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Calculations (updated 2/19)

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  1. Calculations (updated 2/19)

  2. Calculating Amount Needed • Tablets for suspension • Percentage preparations • Aliquots • Alligation • Solubility • Specific gravity • Capsule packing Will go over in PPC

  3. Equivalent Measurements • Tsp = 5 mL • Tbsp = 15 ml • 1 fl oz ~ 30 mL • 1 pint = 473 mL • 1 oz = 28.4 g • 1 lb = 454 g • 1 grain ~65 mg • % (w/v) = g/100 mL • % (v/v) = mL/100 mL • % (w/w) = g/100 g

  4. Tablets for Suspension • Patient needs a lisinopril suspension at 15mg/5ml. He will be taking 5ml po daily. How many lisinopril tablets will be needed to make 30 days worth? • What strength tablets will you need? • 15mg/5mlfor30 days = 450mg/150ml • Can use 11- 40mg tabs + 1- 10mg tab

  5. Tablets for Suspension • Prescription is written for levothyroxine 0.1mg/mL; dispense 60 mL. • We have 25mcg tabs of levothyroxine available • How many tablets will we need to use? • 60mL x 0.1mg/mL = 6 mg of levo • 6mg levox (1 tab/0.025mg levo) = 240 tabs

  6. Tablets for Suspension • What if you need a partial tablet? • Example: Compounding formula calls for 4.8 tablets of ABC. How do we get this? • Weigh out 5 tablets (example = 1.255 g) • Create proportion equation • 1.255 g = xg 5 tabs 4.8 tab • x = 1.2048 g needed

  7. Percentage Preparations • Prescription is written for 1 lb cream (454g) with urea 10% and hydrocortisone 2%. • How much urea and hydrocortisone is in the cream in grams? • Urea: 45.4g; hydrocortisone: 9.08g • How much cream will you need? • 454 – (45.4+9.08) = amount of cream = 399.52g

  8. Percentage Preparations • How many mL of hydrocortisone liquid (40mg/mL) will be needed to prepare 30 grams of a 0.25% cream (w/w)? • 0.25g/100g x 30g = 0.075g HC needed • 75mg HC x (1mL/40mg) = 1.875mL liquid needed

  9. Aliquots • What if what you need to weigh is <120mg? • Example: Rx calls for 7.5mg of ABC in preparation. How do we measure this? • Min weighable qty on our balance: 120mg • To make it easier, most pharmacies do aliquots in % (ie. 1%, 10%) • In this case, to make aliquot we can make a 1g/100g mixture to equal ABC 1% • How much do you need to weigh of ABC 1% to equal 7.5mg? • 750mg (check 750mg x 0.01 = 7.5mg)

  10. Documentation of Compound • Complete name of drug/source used • Name of manufacturer • Lot number of drug source • Expiration date of source • Amounts of materials used • Total amount at top of table • Information placed on back of the rx or in a log book

  11. Documentation of Compound • T-Bar • Line between numbers represent decimal place • Pharmacy compounding log or worksheet • Always include units! (mL, g, etc.) • When calculating, do not round until making a measurement

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