Pharm Calculations Exam 1 Flashcards
Percentage of Error formula
Error x 100% / qty desired
Sensitivity Requirement (SR) is
The minimum weight which will move the index across one subdivision on the index plate.
Minimum Weighable Qty (MWQ) formula
MWQ = 100 x sensitivity requirement / acceptable percentage error
For percentage strength, what are the units of weight-in-volume (w/v)?
g/100mL
For percentage strength, what are the units of volume-in-volume (v/v)?
mL/100mL
For percentage strength, what are the units of weight-in-weight (w/w)?
g/100g
How many grams of a drug are required to prepare 2 liters of a 4% (w/v) solution?
80 g
What is the percentage strength of Normal Saline?
0.9% (w/v) means there are 0.9 g (900 mg) of NaCl in 100 mL of normal saline.
What does 20% (v/v) alcohol solution mean?
There are 20 mL of alcohol in 100 mL of alcohol solution.
What is percent in weight used for?
Used for solids in solids, such as ointment, but sometimes liquids, such as acids or heavy liquids
What is USP?
tolerance permitted in the labeled quantities of ingredients
Range is expressed for many drugs: 95%- 105%
Example:
“Ibuprofen Tablets contain not less than 95% and not more than 105% of the labeled amount of ibuprofen.”
A pharmacist needs to make 10% (w/w) zinc oxide ointment with 5 g of zinc oxide. How many grams of vaseline base (no active ingredient) are needed?
vaseline base = 50 g - 5 g = 45 g
What is mg%?
Number of mg in 100 mL (mg/dL)
A person’s blood test reveals that his blood glucose is 500 mg%. How many grams of glucose are in each 100 mL of his blood?
Ration Strength: How would you interpret:
1/1000 as:
solid in liquid
liquid in liquid
solid in solid
1/1000 is interpreted as:
For solid in liquid: 1 gram in 1000 mL
For liquid in liquid: 1 mL in 1000 mL
For solid in solid: 1 gram in 1000 grams
How is potency of products usually expressed?
Potency of many products is expressed in terms of units – biologic activity.
How many mL of a heparin sodium injection containing 200,000 units in 10 mL should be used to obtain 5,000 heparin sodium units that are to be added to an intravenous (IV) dextrose solution?
0.25 mL
Corticotropin injection is available in a concentration of 40 units/mL. How many mL of the injection should be administered to provide 0.4 unit/kg for a child weighing 66 lb?
0.3 mL
If 10 mcg of ergocalciferol represent 400 units of vitamin D, how many 1.25 mg ergocalciferol capsules will provide a dose of 200,000 units of vitamin D?
4
What is a stock solution?
a relatively concentrated solution of a medicinal or non-medicinal substance used as the source of that substance to prepare a solution of lesser concentration. They are prepared on a weight-in-volume basis, and their concentration is expressed as a ratio strength or, as percentage strength.
What is Alligation?
A method of solving problems that involves the mixing of solutions or mixtures of solids possessing different percentage strengths.
What are the two types of alligation?
Alligation medial
Alligation alternate
What is alligation medial?
A method by which the average percentage strength of a mixture of two or more substances whose quantities and concentrations are known may be calculated.
What is alligation alternate?
A method to calculate the number of parts of two or more components of a given strength when they are to be mixed to prepare a mixture of desired strength. A final proportion allows the translation of relative parts to specific denominations.
