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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5334_Библиотеки_им_академика_М_И_Перельмана
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(w/v) of an isotonic solution of boric acid.
Sodium chloride is a 2-ion electrolyte, dissociating 90% in a certain
concentration. Calculate (a) its dissociation factor and (b) the freezing
point of a molal solution.
A solution of anhydrous dextrose (m.w. 180) contains 25 g in 500 mL
of water. Calculate the freezing point of the solution.
Procaine hydrochloride (m.w. 273) is a 2-ion electrolyte, dissociating
80% in a certain concentration.
a. Calculate its dissociation factor.
b. Calculate its sodium chloride equivalent.
c. Calculate the freezing point of a molal solution of procaine
hydrochloride.
The freezing point of a molal solution of a nonelectrolyte is −1.86°C.
What is the freezing point of a 0.1% solution of zinc chloride (m.w.
136), dissociating 80%? (For lack of more definite information,
assume that the volume of the molal solution is approximately 1 liter.)
How many milligrams of sodium chloride should be used in
compounding the prescription?
How much sodium chloride should be used in compounding the
prescription?
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How much boric acid should be used in compounding the
prescription?
How many milliliters of the buffer solution (E = 0.30) should be used
to render the solution isotonic? (For lack of more definite
information, assume that the specific gravity of the buffer solution is
1.)
How many grams of sodium chloride should be used in preparing the
solution?
A sterile ophthalmic solution contains 2% w/v sulfacetamide sodium
(E = 0.25) in a 5-mL container. Calculate the quantity of sodium
chloride required for isotonicity.
Calculate the effective quantity (g) of sodium chloride related to
tonicity in 100 mL of an intravenous fluid labeled “5% dextrose in
0.45% sodium chloride,” and indicate whether the solution is isotonic,
hypotonic, or hypertonic.
How many milligrams of sodium chloride should be used in
compounding the prescription?
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How much boric acid should be used in compounding the
prescription?
How many milligrams of boric acid should be used in compounding
the prescription?
How many grams of sodium chloride should be used in compounding
the prescription?
How many milliliters of a 0.9% solution of sodium chloride should be
used in compounding the prescription?
22.
How many milliliters of a 5% solution of boric acid should be used in
compounding the prescription?
How many grams of dextrose monohydrate should be used in
compounding the prescription?
How many milligrams of sodium chloride should be used in
compounding the prescription? Use the freezing point depression
method or the sodium chloride equivalent method.
How many milligrams of sodium chloride should be used in
compounding the prescription?
How many milligrams of sodium chloride may be used in the
preparation of 15 mL of an eye drop containing 1% tropicamide and
0.5% chlorobutanol to render the solution isotonic with tears?
a. 18 mg
b. 31.5 mg
c. 103.5 mg
d. 135 mg
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How many grams of sodium chloride should be used in preparing the
solution?
How many grams of anhydrous dextrose should be used in preparing
1 liter of a ½% isotonic ephedrine sulfate nasal spray?
You have on hand an isotonic buffered solution, pH 6.5. How many
milliliters of purified water and how many milliliters of the buffered
solution should be used in compounding the prescription?
The 2% solution of tetracaine hydrochloride is already isotonic. How
many milliliters of a 0.9% solution of sodium chloride should be used
in compounding the prescription?
Determine if the following commercial products are hypotonic,
isotonic, or hypertonic:
a. An ophthalmic solution containing 40 mg/mL of cromolyn
sodium and 0.01% of benzalkonium chloride in purified water.
b. A parenteral infusion containing 20% (w/v) of mannitol.
c. A 500-mL large-volume parenteral containing D5W (5% w/v of
anhydrous dextrose in sterile water for injection).
For agents having the following sodium chloride equivalents,
calculate the percentage concentration of an isotonic solution:
a. 0.20
b. 0.32
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c. 0.61
How many milliliters each of purified water and an isotonic sodium
chloride solution should be used to prepare 30 mL of a 1% w/v
isotonic solution of fentanyl citrate (E = 0.11)?
Using the E-values in Table 11.1, calculate the number of milliliters
of water required to make an isotonic solution from 0.3 g of each of
the following:
a. Antipyrine
b. Chlorobutanol
c. Ephedrine sulfate
d. Silver nitrate
e. Zinc sulfate
Calculate the E-values for each of the following, given that the
number of milliliters of water shown will produce an isotonic solution
from 0.3 g of drug substance.
a. Apomorphine hydrochloride, 4.7 mL water
b. Aminocaproic acid, 8.7 mL water
c. Prilocaine hydrochloride, 7.7 mL water
d. Procainamide hydrochloride, 7.3 mL water
e. Gentamicin sulfate, 1.7 mL water
COSOPT ophthalmic solution contains dorzolamide hydrochloride
22.26 mg/mL, timolol maleate 6.83 mg/mL, benzalkonium chloride
0.0075% w/v, and mannitol for tonicity.13 Dorzolamide hydrochloride
has a molecular weight of 360.91 and is a 2-ion electrolyte that
dissociates 78% in a certain concentration. The E-values for the other
ingredients can be found in Table 11.1. How much of each ingredient
would be needed to prepare enough solution to fill 500 10-mL
bottles?
Calculations of Buffer Solutions
The dissociation constant of ethanolamine is 2.77 × 10−5 at 25°C.
Calculate its pKb value.
What is the pH of a buffer solution prepared with 0.055 M sodium
acetate and 0.01 M acetic acid? The pKa value of acetic acid is 4.76 at
25°C.
What molar ratio of salt to acid would be required to prepare a buffer
solution with a pH of 4.5? The pKa value of the acid is 4.05 at 25°C.
What is the change in pH on adding 0.02 mol of sodium hydroxide to
a liter of a buffer solution containing 0.5 M of sodium acetate and 0.5
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M acetic acid? The pKa value of acetic acid is 4.76 at 25°C.
The molar ratio of salt to acid needed to prepare a sodium acetate–
acetic acid buffer solution is 1:1. Assuming that the total buffer
concentration is 0.1 mol/L, how many grams of sodium acetate (m.w.
82) should be used in preparing 2 liters of the solution?
What is the change in pH with the addition of 0.01 mol hydrochloric
acid to a liter of a buffer solution containing 0.05 M of ammonia and
0.05 M of ammonium chloride? The Kb value of ammonia is 1.80 ×
10−5 at 25°C.
Calculate the pH of the following buffer:
The pKa value of sodium phosphate monobasic is 7.21 at 25°C and
serves as an acid in this buffer because it is more acidic than sodium
phosphate dibasic. The molecular weight of sodium phosphate
monobasic is 120 and of sodium phosphate dibasic is 142.
What is the pH change in the buffer in problem 39 if 3 mL of a 5-M
hydrochloric acid solution are added to the buffer? Assume negligible
volume displacement by the hydrochloric acid solution.
CALCQUIZ
11.A. A 3-mL container of a 0.5% ophthalmic solution of moxifloxacin
hydrochloride (m.w. 401; i = 1.8) is prepared in an aqueous solution of
0.45% sodium chloride. Calculate the quantity, in milligrams, of boric acid
required to render the solution isotonic.
11.B. How many grams of boric acid should be used to render this
prescription isotonic?
11.C. A formulation pharmacist has developed an injection for dental local
anesthesia that contains the following agents:
Using the following data, determine the total tonic effect, expressed in
terms of percent strength of “sodium chloride” or its equivalent.
Lidocaine hydrochloride (E = 0.2)
Epinephrine bitartrate (E = 0.18)
Potassium metabisulfite (m.w. 222; i = 2.6)
Edetate disodium (m.w. 372; i = 2.6)
11.D. A FLEET saline enema delivers in each 118 mL 19 g monobasic
sodium phosphate (monohydrate) and 7 g dibasic sodium phosphate
(heptahydrate). Calculate the product's percent strength in terms of
“sodium chloride or its equivalent,” and indicate whether the enema is
hypotonic, isotonic, or hypertonic.
11.E. What would be the pH of a buffer solution prepared with 0.5 M
dibasic sodium phosphate and 1 M monobasic sodium phosphate? The pK
a
of monobasic sodium phosphate is 7.21 at 25°C.
ANSWERS TO “CASE IN POINT” AND
PRACTICE PROBLEMS
Case in Point 11.1
a.
b. Sodium chloride m.w. = 58.5
Amikacin m.w. = 781.76
c. 1.5 g (amikacin sulfate) × 0.108 (NaCl equivalent) = 0.162 g
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0.54 g − 0.162 g = 0.378 g sodium chloride required for isotonicity
d.
Case in Point 11.2
a. On the basis of 80% dissociation, 100 particles of tobramycin sulfate
will yield:
80 × 2 = 160 tobramycin ions
80 × 5 = 400 sulfate ions
20 undissociated particles
580 total particles
b.
Amount range = 190.2 to 221.7 mg tobramycin activity
c.
d. 300 mg tobramycin sulfate × 0.132 = 39.6 mg sodium chloride
equivalent
100 mg diclofenac sodium × 0.184 = 18.4 mg sodium chloride
equivalent
39.6 mg + 18.4 mg + 806 mg = 864 mg sodium chloride equivalent
Since 100 mL of an isotonic solution would contain 0.9 g or 900 mg of
sodium chloride, the solution is slightly hypotonic. According to the
calculations of E-values for the ingredients, an additional 900 mg –
864 mg = 36 mg of sodium chloride should be added.
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e.
Tobramycin sulfate: 300 mg × 0.2 = 60 mg
Diclofenac sodium: 100 mg × 0.2 = 20 mg
Sodium chloride: 806 mg × 0.2 = 161.2 mg
Sterile water for injection: qs 20 mL
f.
Practice Problems
1.73% w/v
a. 1.9
b. −3.53°C
−0.52°C
a. 4.a. 1.8
b. 0.21
c. c.−3.35°C
−0.036°C
210 mg sodium chloride
226.35 mg sodium chloride
500.77 mg boric acid
0.113 mL buffer solution
4.5 g sodium chloride
20 mg sodium chloride
1.35 g sodium chloride; hypertonic
108.6 mg sodium chloride
469.23 mg boric acid
210.58 mg boric acid
0.69 g sodium chloride
7.67 mL sodium chloride solution
4.56 mL boric acid solution
1.53 g dextrose monohydrate
186.21 mg sodium chloride (freezing point method) or 189 mg
sodium chloride (sodium chloride equivalent method)
153.7 mg sodium chloride
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