# PTCB Pharmacy Calculations #2

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#### What is the percent of hydrocortisone in the final combination if 60 gm of 1% hydrocortisone is mixed with 80 gm of 2.5 % hydrocortisone?

Correct! Wrong!

Explanation:
Hydrocortisone concentration in 60 gm: 1%
Hydrocortisone (60/100) = 0.6 gram
2.5 percent hydrocortisone content in 80 gram
2 gm hydrocortisone = 80 x 2.5/100
the amount of hydrocortisone in the final combination as a percentage
= 100 x 2.6 (2gm + 0.6gm)/140 (80gm + 60gm)
= 1.85% w/w.

#### How much sodium bicarbonate powder is needed to make 240cc of sodium bicarbonate solution at 0.10 N?

Correct! Wrong!

Explanation:
Normality is defined as the number of gram equivalent weights of solute in one liter of solution, therefore a 1N solution of sodium bicarbonate will contain 84 gms in 1000 cc. We need to know how much sodium bicarbonate is in a 240cc, 0.1 N solution:
1 N solution contains 84 gm
0.1 N solution contains ?
= 0.1 x 84 = 8.4 gms/1000cc.
240cc solution will contain:
= 240 x 8.4/1000 = 2.016 gm of NaHCO3

#### To make a 30 percent of 500cc alcohol solution, how many cc of 75 percent alcohol should be mixed with 10% of 1000cc alcohol?

Correct! Wrong!

Explanation:
To solve this type of problem, we need to use alligation method.
75 20 (75%)
30
10 45 (10%)
Total parts 65 (30%)
To prepare 65 (30%) 20 parts (75%) need
To prepare 500 (30%) ?
= 500 x 20/65 = 153.84cc (75%) alcohol
If we mixed 153.84 cc of 75% alcohol with 346.16cc [500cc - 153.84] of 10% alcohol, then we can get 500cc of 30% alcohol solution.

#### In a 0.9 percent 250cc normal saline solution, how many meq of Na+ are present? [Na+ = 23, Cl- = 35.5]

Correct! Wrong!

Explanation:
In 250 cc of 0.9 percent NaCl, there is a certain amount of sodium chloride.
2.25 gram NaCl = 250 x 0.9/100
Na+ = weight in grams = total equivalents
wt equivalent
0.03846 equivalents = 2.25/58.5

#### What would the retail price of 30 Risperdal 1 mg tablets be if 1000 tablets cost \$ 2250 and the percent markup on prescription is 20%?

Correct! Wrong!

Explanation:
Risperdal 1mg tablets cost \$ 2250 for 1000 tablets. The percentage markup on prescriptions is 20%.
As a result, the retail price of 1000 tablets would be as follows:
** For each \$ 100 cost = \$120 retail cost** = 120 x 2250/100 = \$ 2700
The cost of 30 tablets would be:
\$ 81 = 30 x 2700/1000

#### What is the dose of a drug in cc for a 15-month-old infant if the dropper is calibrated to give 325 mg of iron sulfate in 0.6 cc and the adult dose of the drug is 325 mg?

Correct! Wrong!

Explanation:
0.06cc. Fried's rule is as follows:
12 months of age multiplied by 150 x adult dose
32.5 mg = 15 x 325/150
Because the dropper is calibrated to give 325 mg of Iron sulfate in 0.6 cc:
0.06cc = 0.6 x 32.5/325

#### How much atropine is needed to make 240cc so that 1 teaspoonful of the solution diluted to 1 pint yields a 1 in 500 solution?

Correct! Wrong!

Explanation:
To address a situation like this, we must first determine the amount of medication contained in the final solution.
1 pint of atropine contains 1 in 500 soln of atropine.
0.96 gm atropine = 480 x 1 /500
Because 0.96 grams of drug must be present in 1 teaspoonful of drug solution, we can conclude:
0.96 gram in 5cc (1 teaspoonful).
240cc solution requires
= 240 x 0.96/5 = 46.08 gm of atropine.

#### What is the PH of the solution if the ratio of ionized to unionized drug species is 103 and PKa = 2.2?

Correct! Wrong!

Explanation:
The following formula can be used to determine the pH of a solution:
pH = log ionize/unionize + pKa
= log 103 + 2.2
= 2.2 + 3
= 5.2

#### What is the likelihood of failure if the probability of success in the Null hypothesis is 0.6?

Correct! Wrong!

Explanation:
In the Null hypothesis, the total of the probabilities of success and failure equals 1 and can be represented using the following formula:
p + q = 1, where p is the chance of success and q is the probability of failure.
q = probability of failure
q = 1 - p
= 1- 0.6
= 0.4

#### How many 250 mg/100cc ready infusion-bags are required to satisfy the above request if the drug's dose is 10 mg/kg/day? The patient is 156 pounds.

Correct! Wrong!

Explanation:
Because the patient's weight is 156 pounds, the weight in kilograms is 156/2.2 = 70.9 kilograms.
A usual medically recommended dose of medication is 10mg/kg/day, hence the dose in the patient mentioned above is 10mg/kg/day.
= 10 x 70.9
= 709 mg
Because each ready-infusion-bag contains 250 mg of medication, the total number of bags needed to satisfy an order is:
= 709/250 = 2.83 = 3 bags.

#### How much cocabutter is needed to distribute 12 tannic acid suppositories, each weighing 2 gm and containing 400 mg of tannic acid?

Correct! Wrong!

Explanation:
We'd like to give out 12 suppositories, each weighing 2 grams and containing 400 milligrams of tannic acid:
Amount of coca butter = 2 gm x 12
= 24 gm
Amount of tannic acid = 0.4 gm x 12
= 4.8 gm.
Tannic acid has a displacement value of 0.9, so:
= 4.8/0.9 = 5.33 gm of base will displace
4.8 gm tannic acid = 5.33 gm cocabutter
Coca butter quantity = 24 gram - 5.33 gm
= 18.67 gm