Pharm Tech Calculations
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 What is w/w?

Weight in weight
used when the final product is a solid (powder oint etc) and the component you are measuring the % is also a solid. Units in the numerator and denominator must be the same. (ie lb/lb)  What is v/v?

Volume in volume.
is used when the final product is a liquid (solution) and the component you are measuring the % of is also a liquid. Units in the numerator and denominator must be the same (ie ml/ml)  How many liters of a 1:20 dextrose solution contain 100g of dextrose?

100g 1g
______ = _____
? 20ml
?=100g x 20/1
2000ml or 2 liters  How many ml of ethanol are in 35ml of a 1:2 v/v ethanol solution?

1ml ethanol ?
___________ = ________
2ml solution 35ml solu
1mlx35/2
?=17.5ml ethanol 
1 ounce = _____ grains
1 pound = _____ grains 
437.5 grains
7000 grains 
Using the alligation method,
calculate how many parts of 5% and 20% ointments you will need to make a 10% final product. 
20% (10%)= 5 parts of 20%
5%(subtracted from 10%)= 10 parts of 5%  If a label on a vial reads "add 9.2ml of diluent to the vial to get 10ml of a 100mg/ml solution for injection." How many ml of the reconstiututed solution would provide a 250mg dose?

100mg x
_____ = _____ x=1000mg/vial
1ml 10ml
1000mg 250gm
______ = ______
10ml x
x=2.5ml  what is the celsius to fahrenheit temp conversion formula?

9(ºC)=5(ºF)160
converting degrees C to degrees F
ºF = 32 + 5/9
Converting degrees F to degrees C
ºC = 5/9 (ºF32)  How much water would you add to 100ml of a 15% kcl solution to get a 5% final product?

(100ml)(15%) = (X)(5%)
(100ml)(15%)
____________ = x
(5%)
x=300ml total 100ml 15% 200ml of H2O  if an I.V. order is for 500ml of D5 NS to be given over 4 hours (240 min) & the I.V. set delivers 15 drops per ml, what would the flow rate be?

15gtts x
______ = ______ x=7500 gtts
1ml 500ml
7500 x
_____ = _____ x= 31gtts/min
240min 1min 
1 scruple = ____ grains
1 dram = ___ scruples
1 ounces = _____ drams

1 scruple = 20 grains
3 scruples = 1 dram
8 drams = 1 ounce 
1 teaspoon = ____ml
1 Tablespoonful = ____ml

5
15  convert 39ºF to celcius

9(ºC) = 5(39)  160
9(ºC) = 195160
9(ºC) = 35
ºC=35/9
ºC=3.9 
1 gram = ______ grains
1 grain = ____ mg
1 pound = _______gms
1 kg = _______pounds 
1 gm = 15.4 grains
1 grain = 65 mg
1 pound = 454 gms
1kg = 2.2 pounds  Check the validity of the DEA number AP1857397

It has 2 letter and 7 digits
Sum of 1,3,5 digits = 9 (sum1)
sum of 2,4,6 digits = 24
24 X 2 = 48 (sum 2)
48+9 = 57 (sum3)
the 7th digit is a 7
The number is valid.  Convert 80º C to ºF.

9(80)=5(ºF)160
5(ºF)=720+160
5(ºF)= 880/5
ºF = 176
 How many liters of a 5% dextrose solution contain 100g of dextrose?

5g 100g
___ = _____ 100g x 100ml/5gm
100ml ?
2000ml  what is the ratio strength (w/v) of a solution with 2 g of drug in 50ml of solution?

1g 2g
___ = ___
? 50ml
1g x 50/2
25ml
ratio is 1:25  How many grams of dextrose are in 50ml of a 5% w/v solution?

5g = ?
____ ____ 5gx50ml/100ml
100ml 50ml
2.5 gms  How many grams of lidocaine are in 75 g of a 1:50 w/w ointment?

1g lido ?
________ = ________
50gm oint 75g oint
?=1gx75/50
?=1.5g lidocaine  How many ml of ethanol are in 35ml of a 70% v/v ethanol solution?

70ml ethanol ?
____________ = _______
100ml solution 35ml sol
70 x 35/100
24.5ml of ethanol  How many grams of lidocaine are in 75g of a 2% w/w ointment?

2g lido ?
_______ = ________
100g oint 75g oint
2 x 75/100
1.5 g of lidocaine  What is w/v?

Weight in volume is used when the final product is a liquid as indicated by the v in the denominator and the component your are measuring the % of is a solid as indicated by the w in the numerator. The numerator is always in grams and the denominator is always in ml.
EX: 17g of drug K in 100ml of a final solution would be 17g/100ml=0.17or 17%w/v  How many gms of a 1:100 hct crm contain 0.5g of hct?

1 g hct 0.5g hct
_______ = _________
100g cr ?
?=100gx0.5/1
?=50gm of cream  How much nacl is in 200ml of a 1:111 solution?

1g ?
_____ = ______
111ml 200ml
?=1gm x 200/111
?= 1.8gm 
1 fluid ounce = _____ ml
1 pt = ______ml
1 gal = ______ ml 
30ml
473ml
3785ml  What is the formula for checking the validity of a DEA number?

DEA # should contain 2 letters & 7 #.
Add digits 1,3 & 5 to get sum 1
Add digits 2,4 & 6 & multiply x2 this is sum 2.
Add sum 1 & 2 this is sum 3.
In a valid DEA #, the 7th digit will be the 2nd digit of sum 3. If not, the DEA # is not valid.