Ch. 10 Calculations 2
mEq =
(mg x valence)/MW or mmols x valence
# of dissociation particles -dextrose -mannitol -potassium chloride (KCl) -Sodium chloride (NaCl) -Sodium acetate (NaC2H3O2) -Magnesium sulfate (MgSO4) -Calcium chloride (CaCl2) -Sodium Citrate (Na3C6H5O7)
- dextrose: 1 -mannitol: 1 -potassium chloride (KCl): 2 -Sodium chloride (NaCl): 2 -Sodium acetate (NaC2H3O2): 2 -Magnesium sulfate (MgSO4): 2 -Calcium chloride (CaCl2): 3 -Sodium Citrate (Na3C6H5O7): 4
express 0.00022% as PPM
0.00022/100 = X/1,000,000 2.2 PPM
express 0.04% as a ratio strength
0.04/100 = 1 part / X parts x = 2,500 ratio strength is 1:2,500
How many ml of hydrocortisone liquid (40mg/ml) will be needed to prepare 30g of a 0.25% cream (w/w)?
0.25g/100g=x/30g --> 0.075g 40mg/1ml=75mg/x --> 1.88ml
NS is _____% NaCl
0.9%
What is the osmolarity, in mOsmol/L, of normal saline? MW = 58.5
0.9g/100ml = Xg/1000ml --> X = 9g mOsmol/L = 9g/58.5 x 2 x 1000 = 308 mOsmol/L *mOsmol/L - you need normalize to 1 Liter
express 1:4,000 as a percentage strength
1 part/4,000 parts = X/100 0.025%
How many milliosmoles of CaCl2 (MW = 111) are represented in 150ml of 10% (w/v) calcium chloride solution?
10g/100ml = X/150ml --> X=15g mOsmol = 15g/111 x 3 x 1000 = 405 mOsmol
How many mg of iodine should be used in the script? Iodine 1:400 Hydro oint qs ad 10g
1part/400parts = x/100 --> 0.25% 0.25g/100g=x/10g ---> 0.025g --> 25mg
A pharmacist adds 5.3g of hydrocortisone to 150g of 2.5% hydrocortisone ointment. What is the percentage (w/w) of hydrocortisone in the finished product?
2.5g/100g=x/150g --> x = 3.75g total hydrocort = 3.75+5.3 --> 9.05g total weight = 5.3g + 150g --> 155.3g w/w% = 9.05g/155.3g=x/100g ---> 6%
A 20ml vial is labeled KCl (2mEq/ml). How many grams of KCl (MW = 74.5) are present?
20ml * 2mEq/ml = 40 mEq KCl total 40mEq = Xmg * 1 valence / 74.5 X= 2980mg ---> 2.98g
How many g of petrolatum should be added to 250g of 20% ichthammol ointment to make 7% ointment?
250g x 20% = X x 7% --> 714.3g 714.3g-250g = 464.3g
Prepare a 3% w/w coal tar preparation; qs w/ petrolatum to 150g - How many g of petrolatum are required to compound the script?
3g/100g = x/150 x=4.5g coal tar 150-4.5 = 145.5 petrolatum
What is the concentration, in ratio strength, of a trituration made by combining 150mg of albuterol and 4.05g of lactose?
4.05g + 0.15g = 4.2g 0.15g/4.2g = 1part/xpart ---> x=28 --> 1:28
D5W percent dextrose D20W percent dextrose
5% dextrose 20% dextrose
D5NS percents D51/2NS
5% dextrose, 0.9% NaCl 5% dextrose, 0.45% NaCl
A pharmacist has an order for parenteral nutrition that includes 550ml of D70% but only has D50% available. How many ml of D50% will provide an equivalent energy requirement?
550ml x 70% = X x 50% X= 770ml
What is the percentage strength of imiquimod in the script? Imiquimod 5% cream 15g Xylocaine 20g hydrophilic oint 25g
5g/100g *15g = 0.75g of imiquimod 0.75g/60g = x/100g ---> 1.25g, 1.25%
Reconstitute a 5g vial of vanc powder w/ 50ml of water, then dilute w/ water to 200ml. What is the final % strength (%w/v)?
5g/200ml=x/100ml x=2.5g or 2.5%
mOsmol/L =
= (wt of substance (g/L) / MW (g/mole)) x # of particles x 1,000
Sodium chloride equivalent "E value"
E = (58.5)(i)/(MW of drug)(1.8) i = dissociation factor
PPM to percentage strength
Move decimal left 4 places
Percentage strength to PPM
Move the decimal RIGHT 4 places
A pharmacist is asked to prepare 1 gallon of tincture containing 5.5% iodine. The pharmacy has 3% iodine tincture and 8.5% iodine tincture. How many ml of 3% and 8.5% iodine tincture should be used? (1 gallon = 3785ml)
Set up alligation box 8.5% 2.5 parts of 8.5% Xml 5.5% desired 3% 3 parts of 3% Xml =5.5 parts of 5.5% 3785ml 3785ml / 5.5 parts = 688.2ml per part 2.5 parts * 688.2ml = 1720ml of 8.5% iodine 3 parts * 688.2ml = 2065ml of 3% iodine
The E value for ephedrine is 0.23. How many grams of NaCl are needed to compound the script? Ephedrine 0.4g NaCl q.s. Purified water 30ml
Step 1: determine how much NaCl would make the product isotonic 0.9g/100ml = X/30ml -----> x=0.27g Step 2: determine amount of NaCl represented in ephedrine 0.4g*0.23 = 0.092g of NaCl Step 3: 027g - 0.092g = 0.178g of NaCl needed to make an isotonic solution
common 2 valence compounds have
calcium, magnesium, iron, or lithium
A hospice pharmacist receives a prescription for 1% morphine sulfate oral solution. She has a 120ml bottle of morphine sulfate labeled 20mg/5ml and a 240ml bottle labeled 100mg/5ml. How much of the 100mg/5ml product must be mixed with the contents of the 20mg/5ml bottle to prepare the desired percentage strength for the pt?
determine % strengths 0.02g/5ml = x/100 x=0.4% 0.1g/5ml=x/100 x=2% 2% 0.6 parts of 2% Xml 1% 0.4% 1 part of 0.4 120ml ratio is 0.6:1 part 1 part of 0.4%/0.6part of 2% = 120ml of 0.4% /Xml of 2% -----> X= 72 ml of 2% morphine sulfate
mols
g/MW
mmols
mg/MW
milliosmoles refers to millimoles refers to milliequivalents refers to
milliosmoles refers to # of particles in a solution millimoles refers to the molecular weight milliequivalents represents the amount (mg) of solute equal to 1/1000 of its gram equivalent weight
Specific gravity (SG) =
weight of substance (g)/weight of equal volume of water (g) ---> g/ml
