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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5576_Библиотеки_им_академика_М_И_Перельмана
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There is a total of 45 parts to prepare the 4500 mL mixture, or 100 mL
per part (4500 mL/45 parts). And the amount of each component may
be calculated by:
6. How many grams of 2.5% w/w hydrocortisone cream should be mixed
with 360 g of 0.25% w/w cream to make a 1% w/w hydrocortisone
cream?
The amount of 2.5% w/w hydrocortisone cream can be determined by
setting up a ratio of parts:Solving by dimensional analysis:
Solving by ratio and proportion:
7. How many grams of zinc oxide powder should be added to 3200 g of a
5% w/w zinc oxide ointment to prepare a 20% w/w zinc oxide ointment?
NOTE: In the alligation alternate diagram, the zinc oxide powder is
100% zinc oxide.
As in the preceding problem, the amount of zinc oxide powder can be
determined by setting up a ratio of parts:
1.
2.
CASE IN POINT 15.2
A
A pharmacist received the following prescription:
The pharmacist has no clindamycin phosphate powder but does have
clindamycin phosphate sterile solution, 150 mg/mL, in vials. From the
label, the pharmacist learns that the solution is aqueous.
a. How many milliliters of the clindamycin phosphate sterile solution
should the pharmacist use in filling the prescription?
b. How many milliliters of 95% v/v of alcohol are required?
c. How many milliliters of water should be added to make 120 mL?
a
Problem courtesy of Warren Beach, College of Pharmacy, The University of Georgia
Athens, GA.
CASE IN POINT 15.3
A pharmacist received the following prescription:
The pharmacist has no hydrocortisone powder but does have a
hydrocortisone cream, 1%. How many grams each of hydrocortisone
cream and AQUAPHOR should be used in filling the prescription?
PRACTICE PROBLEMS
Altering Strength, Stock Solutions, and Alligation Calculations
A farm product contains a 12.5% w/v concentrate of tiamulin
hydrogen fumarate, used to treat swine dysentery when diluted as a
medicated drinking water. How many gallons of medicated water may
be prepared from a liter of concentrate if the final product is to contain
227 mg of tiamulin hydrogen fumarate per gallon?
If a pharmacist added 12 g of azelaic acid to 50 g of an ointment
containing 15% azelaic acid, what would be the final concentration of
azelaic acid in the ointment?
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3.
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13.
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15.
16.
If 400 mL of a 20% w/v solution were diluted to 2 L, what would be
the final percentage strength?
Mupirocin ointment contains 2% w/w mupirocin. How many grams of
a polyethylene glycol ointment base must be mixed with the contents
of a 22-g tube of the mupirocin ointment to prepare one having a
concentration of 5 mg/g?
How many grams of an 8% w/w progesterone gel must be mixed with
1.45 g of a 4% w/w progesterone gel to prepare a 5.5% w/w gel?
Chlorhexidine gluconate is available in different products in
concentrations of 4% w/v and 0.12% w/v. How many milliliters of the
more dilute product may be prepared from each fluidounce of the
more concentrated product?
A pharmacist fills a prescription for 30 g of a 0.1% w/w
hydrocortisone cream by combining a 1% w/w hydrocortisone cream
and a cream base. How many grams of each were used?
How many milliliters of water should be added to 1.5 L of a 20% w/v
solution to prepare one containing 12% w/v of solute?
If two tablespoonfuls of a 10% w/v povidone–iodine solution were
diluted to 1 quart with purified water, what would be the ratio strength
of the dilution?
How many milliliters of a 1:50 w/v boric acid solution can be prepared
from 500 mL of a 5% w/v boric acid solution?
How many milliliters of water must be added to 250 mL of a 25% w/v
stock solution of sodium chloride to prepare a 0.9% w/v sodium
chloride solution?
How many milliliters of undecylenic acid should be added to 30 mL of
a 20% v/v undecylenic acid topical solution to change its
concentration to 25% v/v?
A pharmacy intern is asked to prepare 3 L of a 30% w/v solution. The
pharmacy stocks the active ingredient in 8-ounce bottles of 70% w/v
strength. How many bottles will be needed as the source of the active
ingredient?
How many milliliters of a 10% w/v stock solution are needed to
prepare 120 mL of a solution containing 10 mg of the chemical per
milliliter?
How many milliliters of a 2.0 molar sodium chloride solution would
be needed to prepare 250 mL of 0.15 molar sodium chloride solution?
NEORAL oral solution contains 100 mg/mL of cyclosporine. If a
pharmacist prepares 30 mL of an oral solution containing 10% w/v
cyclosporine, how many milliliters of diluent should be used?
17.
18.
19.
20.
21.
22.
25.
The formula for a buffer solution contains 1.24% w/v of boric acid.
How many milliliters of a 5% w/v boric acid solution should be used
to obtain the boric acid needed in preparing 1 L of the buffer solution?
In filling a hospital order, a pharmacist diluted 1 mL of an
amphotericin B injection containing 50 mg/10 mL with a 5% w/v
dextrose injection to prepare an intravenous infusion containing
amphotericin B, 0.1 mg/mL. How many milliliters of infusion did the
pharmacist prepare?
What would be the concentration of a solution prepared by diluting 45
mL of a 4.2-molar solution to a volume of 250 mL?
A pharmacist combines the contents of a 30-g tube of a 0.5% ointment
and a 90-g tube of a 1.5% ointment of the same active ingredient.
What is the concentration of the mixture?
1
How many milliliters of a 100 mg/mL concentrate of Rhus
toxicodendron extract should be used in preparing the prescription?
If a pharmacist fortified 10 g of a 0.1% w/w tacrolimus (PROTOPIC)
ointment by adding 12.5 g of an ointment containing 0.03% w/w of
the same drug, what would be the percentage strength of the mixture?
a. How much chlorhexidine gluconate should be used in preparing the
prescription?
b. What would be the concentration of chlorhexidine gluconate in the
solution prepared by the pharmacist, expressed as mg/mL?
How many milliliters of a 17% w/v stock solution of benzalkonium
chloride should be used in preparing the prescription?
A pharmacist–herbalist mixed 100-g lots of St. John’s wort containing
the following percentages of the active component hypericin: 0.3%,
0.7%, and 0.25%. Calculate the percent strength of hypericin in the
mixture.
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26.
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28.
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How many milliliters of a lotion base must be added to 30 mL of
oxiconazole nitrate (OXISTAT) lotion 1% w/v to reduce its
concentration to 6 mg/mL?
2
How many milliliters of an 85% w/w solution of lactic acid with a
specific gravity of 1.21 should be used in preparing the prescription?
A pharmacist receives a prescription for 60 g of a 0.75% w/w
bexarotene gel. How many grams each of a 1% w/w bexarotene gel
and gel base must be used?
As a part of a clinical study, a pharmacist is asked to prepare a
modification of a standard 22-g package of a 2% mupirocin ointment
by adding the needed quantity of mupirocin powder to prepare a 3%
w/w mupirocin ointment. How many milligrams of mupirocin powder
are required?
A pharmacist receives an order for 60 mL of an oral solution
containing memantine hydrochloride (NAMENDA) 1.5 mg/mL. She
has on hand a 360-mL bottle of oral solution containing memantine
hydrochloride, 10 mg/5 mL, and a diluent of sorbitol solution. How
many milliliters each of the available oral solution and sorbitol
solution may be used to fill the order?
If a pharmacist added each of the following to 22-g packages of 2%
mupirocin ointment, what would be the percentage strengths of the
resulting ointments: (a) 0.25 g mupirocin powder and (b) 0.25 g of
nonmedicated ointment base? (Answer to two decimal places.)
How many milliliters of liquefied phenol (90% w/w phenol solution,
sp. gr. = 1.07) would be needed to prepare 3 fl.oz. of a 4.5% w/v
solution?
If 1 mL of a 0.02% w/v isoproterenol hydrochloride solution is diluted
to 10 mL with sodium chloride injection before intravenous
administration, calculate the percent concentration of the diluted
solution.
A 1:750 w/v solution of benzalkonium chloride diluted with purified
water in a ratio of 3 parts of the benzalkonium solution and 77 parts of
purified water is recommended for bladder and urethral irrigation.
What is the ratio strength of benzalkonium chloride in the final
dilution?
How many milliliters of a suspension base must be mixed with 250
mL of a paroxetine (PAXIL) oral suspension, 10 mg/5 mL, to change
36.
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44.
its concentration to 0.1% w/v?
A standing institutional order for a 25% w/w topical antibiotic
ointment has been changed to one for a 10% w/w ointment. How
many grams of white petrolatum must be mixed with each 120-g
package of the 25% w/w preparation to make the new 10% w/w
preparation?
How many grams of a 2.5% w/w benzocaine ointment can be prepared
by diluting 1 lb of a 20% w/w benzocaine ointment with white
petrolatum?
How many grams of salicylic acid should be added to 75 g of a
polyethylene glycol ointment to prepare an ointment containing 6%
w/w of salicylic acid?
How many grams of an ointment base must be added to 45 g of
clobetasol (TEMOVATE) ointment, 0.05% w/w, to change its strength
to 0.03% w/w?
How many grams of 2.5% ophthalmic hydrocortisone acetate ointment
and how many grams of ophthalmic base (diluent) should be used in
preparing the prescription?
Thimerosal Tincture USP contains 0.1% w/v thimerosal and 50% v/v
ethyl alcohol. If the cap is left off of a 15-mL bottle of the tincture,
and the ethyl alcohol evaporates leaving a final volume of 9.5 mL,
what is the concentration of thimerosal in the evaporated solution
expressed as a ratio strength?
How much zinc oxide should be added to the product to make an
ointment containing 10% of zinc oxide?
If equal portions of tretinoin gel (RETIN-A MICRO), 0.1% w/w and
0.04% w/w, are combined, what would be the resultant percentage
strength?
A vaginal douche powder concentrate contains 2% w/w of active
ingredient. What would be the percentage concentration of the
resultant solution after a 5-g packet of powder is dissolved in enough
water to make 1 quart of solution?
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45.
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3
How many milliliters of a 0.2% solution of a skin test antigen must
be used to prepare 4 mL of a solution containing 0.04 mg/mL of the
antigen?
How many milligrams of sodium fluoride are needed to prepare 100
mL of a sodium fluoride stock solution such that a solution containing
2 ppm of sodium fluoride results when 0.5 mL is diluted to 250 mL
with water?
4
How many milliliters each of corn oil and a 10% solution of cyclosporine
would be needed to prepare 30 mL of the prescription? (b) If you then
wished to dilute the prescription to a concentration of 1.5% cyclosporine,
how many additional milliliters of corn oil would be required?
A hospital pharmacist is to prepare three doses of gentamicin 0.6 mg/2
mL. In stock is gentamicin 20 mg/mL. How many milliliters each of
the gentamicin on hand and appropriate diluent would be needed?
A hospital worker combined 2 fluidounces of a povidone–iodine
cleaner, 7.5% w/v, with 4 fluidounces of a povidone–iodine topical
solution, 10 % w/v. Calculate the resulting strength of the povidone–
iodine mixture. (Assume volumes are additive.)
If 60 g of a combination gel of hydrocortisone acetate, 1% w/w, and
pramoxine, 1% w/w, is mixed with 12.5 g of a gel containing
hydrocortisone acetate, 2.5% w/w, and pramoxine, 1% w/w, calculate
the percentage strength of each of the two drugs in the mixture.
A drug is commercially available in capsules each containing 12.5 mg
of drug and 37.5 mg of diluent. How many milligrams of additional
diluent must be added to the contents of one capsule to make a
dilution containing 0.5 mg of drug in each 100 mg of powder?
In what proportion should 5% and 1% hydrocortisone ointments be
mixed to prepare a 2.5% ointment?
In what proportion should a 20% zinc oxide ointment be mixed with
white petrolatum (diluent) to produce a 3% zinc oxide ointment?
A parent diluted 1-mL ibuprofen oral drops (Infant’s MOTRIN
Concentrated Drops) with 15 mL of water prior to administering the
medication. The concentrated drops contain ibuprofen, 50 mg/1.25
mL. Calculate the concentration of ibuprofen in the dilution in (a)
mg/mL and (b) as a percentage strength.
55.
56.
57.
58.
59.
60.
How many milliliters of a 2.5% w/v chlorpromazine hydrochloride
injection and how many milliliters of 0.9% w/v sodium chloride
injection should be used to prepare 500 mL of a 0.3% w/v
chlorpromazine hydrochloride injection?
How many milliliters of a 2% w/v solution of lidocaine hydrochloride
should be used in preparing 500 mL of a solution containing 4 mg of
lidocaine hydrochloride per milliliter of solution?
Dopamine hydrochloride injection is available in 5-mL vials
containing 40 mg of dopamine hydrochloride per milliliter. The
injection must be diluted before administration. If a physician wishes
to use sodium chloride injection as the diluent and wants a dilution
containing 0.04% w/v of dopamine hydrochloride, how many
milliliters of sodium chloride injection should be added to 5 mL of the
injection?
A pharmacist is to prepare 10 mL of amikacin sulfate in a
concentration of 0.4 mg/0.1 mL for ophthalmic use. Available is an
injection containing amikacin sulfate, 250 mg/mL. How many
milliliters of this injection and of sterile normal saline solution as the
diluent should be used?
5
How many milliliters of sterile water for injection should be added to
a 1-mL vial containing 5 μg/mL of a drug to prepare a solution
containing 1.5 μg/mL of the drug?
How many milligrams of a 1:10 w/w powdered dilution of colchicine
should be used by a manufacturing pharmacist in preparing 100
capsules for a clinical drug study if each capsule is to contain 0.5 mg
of colchicine?
CALCQUIZ
15.A.a A pharmacist receives a special request from an ophthalmologist
to prepare a fortified tobramycin ophthalmic solution. The available
solution contains tobramycin, 3 mg/mL. How many milliliters of a
tobramycin injection containing 40 mg/mL must be aseptically added to a
5-mL container of the ophthalmic solution to prepare one 0.5% in
concentration?
15.B. How many milliliters of water must be added to 15 mL of a 23.4%
solution of sodium chloride to dilute the concentration to 0.06 mEq/mL?
15.C. How much Peruvian balsam should be added to 3 oz of a diaper
rash ointment containing 4% w/w Peruvian balsam to increase the
concentration to 10% w/w?
15.D. A 60-mL bottle of an oral solution contains a drug in a
concentration of 15 mg/mL. A medication order requests that the drug
concentration be reduced to 5 mg/mL by using three parts water to one
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part polyethylene glycol 400. How many milliliters of each of these two
agents should be used?
15.E. How many milliliters of a 17% solution of benzalkonium chloride
should a pharmacist use in preparing 120 mL of a prescription such that
when a patient adds 15 mL of the dispensed medication to a gallon of
water, as a foot soak, the resulting benzalkonium chloride concentration
will be 1:5000?
a
Problem courtesy of Flynn Warren, Bishop, GA.
ANSWERS TO “CASE IN POINT” AND
PRACTICE PROBLEMS
Case in Point 15.1
Cefuroxime axetil present in original suspension:
Cefuroxime axetil required in strengthened suspension:
Cefuroxime axetil to add:
Tablets required:
A Second Look
There are a number of ways in which this problem could be addressed. One
way would be to add another 250-mg pulverized tablet, calculate the
volume of suspension that could be prepared at a concentration of 300 mg/5
mL, dispense 100 mL of that, and discard the remaining volume.
Cefuroxime axetil in strengthened suspension plus another tablet:
Volume of suspension that could be prepared at a concentration of 300
mg/5 mL:
Because adding four tablets increased the volume by 2 mL, it can be
assumed that one tablet would displace approximately 0.5 mL, creating a
volume of 102.5 mL. Therefore, water or another diluent should be added
to reach a final volume of 104.17 mL.
Volume to dispense: 100 mL
Volume to discard: 4.17 mL
Proof: “If there are 6250 mg of cefuroxime axetil in 104.17 mL, how
many milligrams would be present in each 5 mL?”
Case in Point 15.2
a.
b. Based on the information in the formula, the final concentration of
alcohol in the formulation should be 52% v/v. The amount of 95%
v/v alcohol to create this concentration can be calculated as follows:
c. Due to contraction when alcohol and water are mixed, the volume of
water cannot be determined by subtracting 65.68 mL from 120 mL;
thus, a sufficient volume of water is used (q.s.) to make 120 mL.
Case in Point 15.3
15 g × 0.006 (0.6% w/w) = 0.09 g hydrocortisone
1% hydrocortisone cream = 1 g hydrocortisone/100 g
NOTE: The problem also may be solved by alligation alternate.
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