# PTCB Pharmacy Calculations #2

#### 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?

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?

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?

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]

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%?

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?

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?

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?

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?

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.

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?

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

Comments are closed.