buffers and isotonic solutions

8/12/2019 Buffers and Isotonic Solutions

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Isotonic solutions


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Isotonic solution~ Colligative propertiessimilar to those ofbody fluids

~ Solute are not capable of diffusingthrough biological membrane

Isoosmotic solutionIsotonic - a biological compatibilityisoosmotic - similarity of chemical and/orphysical composition


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The Osmolality of Some BiologicalFluidsFluid Osmolality, mOsmol/kg (mean

SD)

Bile, gallbladder 349 40

Bile, hepatic 28417

Gastric 28222

Feces 35737

Ileal 29212

Jejunal 28510

Pancreatic 32010

Parotid saliva 12735


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Sodium chloride solution 0.9 w/v~A Freezing point depression(t

f)=0.52

Hypotonic solution~-0.52< t

f


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Isoosmotic solution but not isotonicsolutions

~Swelling and bursting of the cells~The solute molecules -> The cells

Ex. Boric acid(1.9%w/v)~Hemolysis to red blood

~Isotonic in the eye


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The Osmolality(mOsmol/kg) of Some

Medicinal PreparationsDrug Concentration Osmolality

Acetaminophen

drops

80mg/0.8ml 10535

Chloral hydratesyrup

50mg/ml 4400

Ferrous sulfate

liquid

75mg/0.6ml 4445

Lactulose syrup 670mg/ml 3600

Vitamin E drops 15IU/0.3ml 3620


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Sodium Chloride Equivalent Values(E)1g drug ? g sodium chlorideE 17(Liso/MW)

Ex7.E value? MW=340g/mole L

iso

=3.4E value=17(3.4/340)=0.17g


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Freezing Point Depression and Sodium ChlorideEquivalent Values for Various Solutes and DrugsConcentration of the solution

Drug or solute Sprowls 0.5% 1% 2% 3% 5% At Isoosmotic

Acetrizoatemethylglucamine

0.090.024

0.080.047

0.080.093

0.080.137

0.080.222

0.070.52

12.12%0%(7.1)

Acetylcysteine 0.20

0.055

0.20

0.113

0.20

0.227

0.20

0.341

0.20

0.52

4.58%

100%(2.0)

0.21

Concentration

Acetaolamidesodium

3.85%0%(9.2)

Acriflavine,N.F.

3.3 0.10 0.09

AdrenaloneHCl 0.27 0.22 4.24%68%(4.5)


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Preparation of Isotonic Solutions

Freezing Point Depression MethodAmount of NaCl needed in 100mL ofsolution = [0.9*(0.52- ]/0 52Ex10. 100ml of a drug solution , How

much NaCl=? Fp=-0.18

Amount of NaCl needed = [0.9*(0.52-

0.18)]/0.52=0.59g


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Sodium Chloride Equivalent MethodStep1: E * (amount of drug in solution) = XStep2: (0.9g/100mL) * (volume of solution in mL) = YStep3: Y X = amount of NaCl neededEx11. 3g/500ml solution of drug(E=0.21), How much NaCl? Torender the solution isotonic.

S1: 0.21 * 3g = 0.63g

S2: (0.9g/100mL) * (500mL) = 4.5g

S3: 4.5 - 0.63 =3.87g


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White-Vincent Method

Wi= weight in grams of the i th solute in the

formulation

Ei= sodium chloride equivalent of the ith solute inthe formula

v = volume of sodium chloride solution (0.9%) that

contains 1g of NaCl (this volume is 111.1 mL)

vEWV ii = )]([


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Ex12

Chloramphenicol (MW = 323.13 g/mole,

Liso=2) 1gSterile water for injection, q.s. ad 100mLM. ft. isotonic solution

sol)E 17(2/323.13) = 0.10Applying the White-Vincent equationV = 1g * 0.10 * 111.1 = 11.1mL


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Sprowls MethodThe Sprowls value

The volume of an isotonic solution thatcan be prepared by the addition of enoughwater to 0.3 g drug

0.3g represents the amount of drug in a

fluid ounce of a 1% solution

1 fluid ounce 0.0294 L


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Ex15.

The Sprowls value of Glycerin = 11.7

The E value of glycerin = ?

sol)

11.7 = 0.3 g * E * 111.1

E = 0.35

vEWV ii = )]([


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Ex15.

How much silver nitrate is needed toprepare 100mL of isotonic solution?

An isotonic silver nitrate solution preparedby the Sprowls method => 13mL

0.3 : 13mL = x : 100mL

0.3g * 100mL / 13mL = 2.3g of silvernitrate

buffers and isotonic solutions

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