1. Percentage concentration
% w/w(weight)----------active ingredient and base have same unit of weight.
1%=1gm of active ingred per 100gm total product.
1% w/w= 1gm/100gm
%v/v(volume)-------solute(active drug) and solvent(inactive base) have same unit
of volume.
1% v/v=1ml/100ml
%w/v(weight/volume)-------solute is in the weight grams and solvent is in
volume ml.
1% w/v=1gm/100ml
2. • 1.4g of phenol mixed with 9g of glycerin. What is %
concentration of phenol in this product?
1.4+ 9g =10.4g
1.4/10.4*100=13% w/w
4g KCL is dissolved in base to make total of 25ml.
What is per concentration of final product?
4/25*100=16%w/v
10ml glycerin is dissolved in enough water to make
73ml of final solution. Calc % of strength of glycerin.
10/73*100=14% v/v
3. • How much KCL is needed to make 240ml of a 10%
solution?
• 10gm/100ml=x gm/240ml
• X=24g of kcl
4. alligations
• Using 2 different concentrations of a drug to arrive
at final concentration somewhere between the 2 in
stock.
• Dr orders 30g of 15% hydrocortisone cream.
Pharmacy has cream in 20% and also 2%. Alligation
will combine these to get 30gm, of 15%.
• See board pg158-------
5. Ratio concentrations
Normally this uses epinephrine or potassium
permanganate.
You must memorize-------
1:1000------1mg/ml
1:100--------10mg/ml
1:10---------100mg/ml
Rx is 3mg of epi. Pharm stock is 1:100 solution. How may
ml will be given?
10mg/ml= 3mg/xml
10x mg=3mg
X=.3ml
6. • Rx 2.5ml inj of 1:1000 epi is given. How much drug
did pt get?
• 1:1000=1mg/ml
• 1mg/ml=x mg/2.5ml
• X =2.5mg
7. Parenteral calculation
• Done for IV drips. This has greater risk of immediate
pt harm if wrong.
• Flow rate=vol/time
• Pt gets 1L of IV sol over 3 hours. What is flow rate?
• Flow rate=1000ml/3hrs
• Fr=333ml/hr --- this means 5.55ml/min
8. • How many hours will 1L of D5W last when flow rate
is 125ml/hr?
• Time=vol/rate
• time=1000ml/125ml
• Time=8hr
• Vol=time *rate
• Hwo many ml needed to run IV at 60ml/hr for 12
hours?
• Vol=12hrs*60mlper hour
• Vol=720ml
9. • Gtt/min=volume to be infused *drip set
rate/infusion time in minutes
• Rx is d5w at 125ml/hr. admin set is 10gtt/ml.
How many gtt/min should we use?
• Gtt/min= 125ml*10gtt/60min
• Gtt/min=1250/60
• Gtt/min=20.8 ~21gtt/min
10. • Gtt/min=volume to be infused *drip set
rate/infusion time in minutes
• 300ml of d5w given at rate of 75ml/hr. admin set
gives 10gtt/ml.how many gtt/min should we use?
• Gtt/min=vol infused*drip rate/infusion time(min)
• Gtt/min= 75ml*10/60
• Gtt/min=750/60
• Gtt/min=12.5gtt/min ~13ggt/min
