concentrationexpresion qm chp6

Expressions of Concentrations

Quamrun Masuda, PhD, RPh

276-498-5241

[email protected]

Reference: Pharmaceutical Calculations (13th edn)

By Howard C Ansel

e-copy: http://thepoint.lww.com/Ansel13e

Chapter 6

mailto:[email protected]

http://thepoint.lww.com/Ansel13e

Learning Objective

After completion of this lesson, students will be able to:

Express concentration of a product in %w/v, %v/v, %w/w and ratio strength.

Express concentration in PPM & convert that to %.

Calculate the %strength and ratio strength of a pharmaceutical preparation.

Apply %strength and ratio strength to calculate the quantity of an ingredient in pharmaceutical compounding.

Percentage (%)

In pharmacy and medicine, percentages are often used for expressing concentrations.

The term ‘percentage’ and its corresponding sign (%) mean “by the hundred” or “in a hundred,” and means “rate per hundred” - from the Latin per centum, meaning “per 100”.

Percentage (%)

Based on General Notices of the USP, unless otherwise stated, percent has the following meanings:

Solids and Semisolids: %w/w — number of grams of solid ingredient in 100 g of solid or semisolid mixture.

Solutions or Suspensions of solids in liquids: %w/v - number of grams of solid ingredient in 100 mL of preparation.

Solutions of liquids in liquids: %v/v — the number of mL of liquid ingredient in 100 mL of solution.

Solutions of gases in liquids: %w/v — the number of grams of gas in 100 mL of solution.

Calculations based on Percentage %(w/v)

How many grams of dextrose are required to prepare 4000 mL of a 5% solution?

Solving by proportional analysis:

Solving by dimensional analysis:

Calculations based on Percentage

How many grams of dextrose are required to prepare 4000 mL of a 5% solution?



dextroseg200mL4000xmL100

dextroseg5

dextrose g200 x,mL 4000

gx

mL100

drugg5


How many grams of aminobenzoic acid should be used in preparing 8 fluidounces of a 5% solution in 70% alcohol?


g11.83ounce fl 1

mL 29.57x ouncefl 8x

mL100

drugg5

rroy

Note

alcohol is nothing but the medium.

Practice Problem: Question # 11

NEUPOGEN (filgrastim) prefilled syringes contain 480 µg

of active constituent in each 0.8 mL. What is the

equivalent %concentration?


LEVAQUIN (levofloxacin) injection contains 5 mg/mL of

levofloxacin and 5% of dextrose. How much of each

would be delivered to a patient upon the administration

of a 100-mL injection?

rroy

Note

dextrose changes the osmalarity. thats why it matters.


How many milliliters of a 3% solution can be made from 27 g of ephedrine sulfate?


Percentage Volume-in-Volume (%v/v)

In preparing 250 mL of a certain lotion, a pharmacist used 4 mL of liquefied phenol. What was the percentage (v/v) of liquefied phenol in the lotion?


Questions

Q1. A formula for an antifungal shampoo contains 2% w/v

ketoconazole. How many grams of ketoconazole would

be needed to prepare 25 liters of the shampoo?


A pharmacist adds 10 mL of a 20% (w/v) solution of a drug

to 500 mL of D5W for parenteral infusion. What is the

percentage strength of the drug in the infusion solution?

rroy

Note

the strength is reduced bcoz it is diluted further.


VIRAMUNE Oral Suspension contains 1% w/v of nevirapine.

Calculate the milligrams of nevirapine present in a 240 mL

bottle of the suspension.

Percentage Weight-in-Weight (%w/w)

How many grams of phenol should be used to prepare 240 g of a 5% (w/w) solution in water?


rroy

Note

if density is given,

Percentage Weight-in-Weight (%w/w)

How many grams of phenol should be used to prepare 240 g of a 5% (w/w) solution in water?

Note: While calculating %w/w of a solution or liquid preparation, the volume, in mL, of the solution represents the weight, in grams, of the solution or liquid preparation, as if it were pure water, unless density or specific gravity of the solution is given.


Hydromorphone hydrochloride suppositories contain 3 mg of

active ingredient and weighs approximately 2 grams each.

What is the equivalent percentage strength?


Rx

Lactic Acid 4 g

Salicylic Acid 5 g

Trichloroacetic Acid 2 g

Flexible Collodion qs ad 100 g

a. Flexible collodion contains 20% w/w camphor and 30%

w/w castor oil. How many grams of each would be

contained in 30 g of the mixture?

Ratio Strength (x:y)

Concentrations of dilute solutions or solid mixtures are sometimes expressed as ratio strengths rather than as percent. Example, 1:10,000.

Ratio strength of 1:1,000 is interpreted as follows:

• For solids in liquids: 1 g of solute in 1,000 mL of solution.

• For liquids in liquids: 1 mL of liquid contains in 1,000 mL of solution.

• For solids in solids: 1 g of solid in 1,000 g of solid mixture.

Express 0.02% as a ratio strength


Express 1:4000 as a percentage strength.

Express 0.02% as a ratio strength


Express 1:4000 as a percentage strength.

5000:1partsx

parts 1

parts 100

parts 0.02

0.025%parts 100

partsx

parts 4000

parts1

A certain injectable contains 2 mg of a drug per milliliter of solution. What is the ratio strength (w/v) of the solution?


Questions

Q2. An ear drop formula contains 54 mg of antipyrine and 14

mg of benzocaine in each milliliter of solution. Calculate

the percentage strength (w/v) of each ingredient in the

formula.


VERSED® Injection contains 5 mg of midazolam per milliliter

of injection. Calculate the ratio strength of midazolam in

the injection.


In acute hypersensitivity reactions, 0.5 mL of a 1:1000 (w/v)

solution of epinephrine may be administered

subcutaneously or intramuscularly. Calculate the

milligrams of epinephrine given.

Milligrams Percent

The term milligrams percent (mg%) expresses the number of milligrams of substance in 100 mL of liquid.

It is used to denote the concentration of a drug or natural substance in the blood.

The concentration of nonprotein nitrogen in the blood is 30 mg% means that each 100 mL of blood contains 30 mg of nonprotein nitrogen.

Parts per Million (PPM) and Parts per Billion (PPB)

The strengths of very dilute solutions are commonly expressed in terms of parts per million (ppm) or parts per billion (ppb), i.e., the number of parts of the agent per 1 million or 1 billion parts of the whole.

For example, in fluorinated drinking water fluoride has been added at levels of between 1 to 4 parts per million (1:1,000,000 to 4:1,000,000) for the purpose of reducing dental caries.

Express 5 ppm of iron in water in percentage strength and ratio strength.

Solving by Proportional analysis:

% Strength:

Ratio Strength:


If a commercially available insulin preparation contains 1

ppm of proinsulin, how many micrograms of proinsulin

would be contained in a 10-mL vial of insulin?

%strength and ratio strength of a pharmaceutical preparation

How many milligrams of hydrocortisone should be used in compounding the following prescription?

Hydrocortisone 1/8%

Hydrophilic ointment ad 10 g

Sig. Apply on affected area

Hydrocortisone strength is 1/8% =0.125%


%strength and ratio strength of a pharmaceutical preparation

How many milligrams of hydrocortisone should be used in compounding the following prescription?

Hydrocortisone 1/8%

Hydrophilic ointment ad 10 g

Sig. Apply

Hydrocortisone strength is 1/8% =0.125%


Use of % in Compendial Standard

USP use % to express the degree of tolerance permitted in the purity of single-chemical entities and in the labeled quantities of ingredients in dosage forms.

e.g. “Aspirin contains not less than 99.5% and not more than 100.5% of C9H8O4 (pure chemical aspirin) calculated on the dried weight basis.”

“Aspirin Tablets contain not less than 90.0% and not more than 110.0% of the labeled amount of C9H8O4.”

Q: If ibuprofen tablets are permitted to contain not less than 90% and not more than 110% of the labeled amount of ibuprofen, what would be the permissible range in content of the drug, expressed in milligrams, for ibuprofen tablets labeled 200 mg each?


If ibuprofen tablets are permitted to contain not less than 90% and not more than 110% of the labeled amount of ibuprofen, what would be the permissible range in content of the drug, expressed in milligrams, for ibuprofen tablets labeled 200 mg each?


Questions

Q3. How many milliliters of a 0.9% (w/v) solution of sodium

chloride can be prepared from 50 tablets, each

containing 2.25 g of sodium chloride?

concentrationexpresion qm chp6

Documents

percentage volume

proportional analysis

term percentage

dimensional analysis

grams of dextrose

grams of solid ingredient

wv number

grams of ketoconazole