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changing the strength of a pharmaceutical preparation
concentration
add active ingredient
admixture with a like preparation of greater strength
evaporation of vehicle (if liquid)
changing the strength
dilution
add diluent
admixture with a like preparation of lesser strength
provide a product strength more suitable for use by a particular patient
elderly or young
same amount active ingredient
-diluent=increase concentration
+diluent=decrease concentration
Strengteh and total quantity
if the amount of active ingredient remains constant, any change in the quality of a solution or mixture of solids is inversely proportional to the percentage or ration strength
increase quantity
percentage or ration strength decreases
decrease quantity
percentage or ratio strength increases
Relationship between total quantity and strength
C1Q1=C2Q2
Stock solutions
concentrated solutions of active or inactive sibstances (increase concentrated)
used as a convenience to prepare solutions of lesser concentrations
"should be added to"
need to subtract amount already present from amount found in Q1C1=Q2C2 equation
Alligation
arithmetical method of solving problems that involves the mixing of slutions or mixtures of solids possessing different percentage strengths
Alligation Medial
percentage strength of each component is multiplied by its corresponding quantity
sum of the products is divided by the total quantity of the mixture
resultant decimal fraction is multiplied by 100 to give percentage strength of mixture
Alligation Alternate
calculate the number of parts of 2 or more components of a given strength when they are mixed to prepare a mixture of desired strength
Alligation Alternate
strength of a mixture (desire) must lie somewhere between the strengths of its components
stronger than its weakest component
weaker than its strongest component
reducing and enlarging formulas
reduce or enlarge formulas for pharmaceutical preparations
offical formulas are based on the preparation of 1000 mL or 1000g
Smaller quantity
reduce formula
greater quantity
enlarge formula
maintain the correct proportion of one ingredient to another
Step 1
Determine the factor that defines the multiple (enlarge) or the decimal fraction(refuce) of the amount of formula to be prepared
Factor=want/have
quantity of formula desired/quantity of formula given
Step 2
Multiply the quantity of each ingredient in the formula by the factor to determine the amount of each ingredient required in the reduced or enlarged formula
Formulas that specify proportional parts
indicate the relative proportion of each of the ingredients in the formula either by eright or volume