# Pharmacy Calculation Questions and Answers (Part-2)

#### Q1. How many milligrams are equal to 1/150  grains?

Answer:  1 grain is equal to 65 mg therefore:

1/150 grains will contain:

= (1 x 65)/150 = 0.43 mg

#### Q2. How many 975 mg tablets of aspirin are required to prepare 100 tablets of 1 grain?

Answer: 100 tablets of 1grain of Aspirin contains: 100 x 65 = 6500 mg of Aspirin.

The number of 975 mg tablets of Aspirin:

= 6500/975 = 6.66 = 7 tablets

#### Q3. If 3 capsules of 150 mg of Clindamycin are added to 150 cc of 1% Cleocin topical solution, what is the % of Clindamycin in the final mixture?

Answer: 1 % 150 cc Cleocin solution contains:

= (150 x 1)/100 = 1.5 gm Clindamycin

The addition of 3 capsules each weighing 150mg will result in: 1.5 gm+ 0.45 gm = 1.95 gm

% of Clindamycin in final mixture would be:

= (1.95 x 100)/150 = 1.3%

#### Q6. What is the pH of a solution having a ratio of ionized to unionized species of drugs of 1 x 10^-6? [PKa = 7]

Answer: pH = pKa + log [salt/acid]

pH = 7 + log[ 10^-6]

= 7 - 6

= 1

#### Q7. The adult dose ofa drug is 500 mg. What is the dose for a 2 year old child? [use young rule]

Answer: Young rule = age in year/(age + 12) x adult dose

= 2/(12+2) x 500 = 71.42 mg

#### Q8. Calculate the dose for a 3-year old child. An adult dose of the drug is 500 mg. [use young rule]

Answer: Young rule = age in year/(age + 12) x adult dose

= 3/(12+3) x 500 = 100 mg,

#### Q10. The usual initial dose of chlorambucil is 150 ug/kg of body weight once a day. How many milligrams should be administered to a person weighing 154 lb?

Answer: We know, 150 ug = 0.15 mg & 1 kg = 2.2 lb;

Thus, 2.2 lb/154 lb = 0.15 mg/ X mg

X = 10.5 mg

#### Q11. If the dose of a drug is 200 mg, how many doses are contained in 10 g?

Answer: 10 g = 10,000 mg

Number of doses  10,000 (mg)/200 (mg) = 50 doses.

#### Q12. If 1 tablespoon is prescribed as the dose, approximately how many doses will be contained in 1 pint of the medicine?

1 tablespoon = 15 mL

1 pint  = 473 mL

Number of doses = 473 mL/15 mL  = 31.5 or 31 doses.

#### Q13. How many drops would be prescribed in each dose of a liquid medicine if 15 mL contained 60 doses? [The dispensing dropper calibrates 32 drops/mL]

15 mL  = 15 x 32 drops = 480 drops

Size of dose = 480 (drops)/60 = 8 drops.

#### Q14. It takes approximately 4 g of ointment to cover an adult patient’s leg. If a physician prescribes an ointment for a patient with total leg eczema to be applied twice a day for 1 week, which of the following product sizes should be dispensed: 15 g, 30 g, or 60 g?

Number of doses  2 per day x 7 days = 14

Size of dose = 4 g

Total quantity  14 x 4 g = 56 g; thus, 60 g product size.