Section 13 - Calculations

Question 1

What are the 3 parts of a number that should always be present?

Answer 1

Value, units, and descriptive name

Question 2

What are the 3 ways to check an answer?

Answer 2

1) Estimate before the calculation and then compare the estimation to the answer
2) Verify the answer by a different method
3) Have 2 people independently perform the calculation and compare answers

Question 3

How can the strength of a pharmaceutical product be increased or decreased?

Answer 3

Changing the proportion of active ingredient to the whole

Question 4

How can dilution problems be solved?

Answer 4

C1V1 = C2V2

Question 5

How can strengthening/blending calculations be solved?

Answer 5

Alligation

Question 6

What is the sensitivity requirement for a prescription balance?

Answer 6

6 mg

Question 7

What is the least weighable quantity w/ an error of 5%?

Answer 7

LWQ = SR / 0.05, so if SR = 6 mg, the LWQ is 120 mg for a typical prescription balance

Question 8

What can be done if a measurement of drug that is needed is below the least weighable quantity?

Answer 8

Mix more of the drug w/ an excipient (trituration) and take an aliquot

Question 9

What are the 5 steps required for capsules?

Answer 9

1) Choose which shell to use
2) Fill capsules w/ each ingredient separately and weigh
3) Calculate diluent displacement weights for all drugs by ratio and proportion
4) Calculate amount of diluent needed
5) Calculate total quantities needed for # of capsules

Question 10

What is a sodium chloride equivalent?

Answer 10

One gram of a given drug will have the same effect on tonicity as that quantity (E value) in grams of sodium chloride

Question 11

What do you get if you multiply a quantity of drug by its E-value?

Answer 11

The quantity of NaCl that the drug will contribute to the tonicity of the product

Question 12

What are the 4 steps to solving a tonicity problem using sodium chloride equivalents?

Answer 12

1) Calculate amount of sodium chloride represented by each ingredient (multiply weight by its E-value)
2) Calculate the amount of NaCl required to make the specified volume isotonic (0.9% NaCl)
3) Subtract the amount of NaCl contributed by each of the ingredients calculated in step 1 from the quantity of NaCl calculated in step 2
4) If a substance other than NaCl is to be used, divide the amount of NaCl calculated in step 3 by the E-value of the other substance

Question 13

Which method is useful for preparation of isotonic solutions if the product is to be buffered?

Answer 13

Isotonicity through volume dilution