Chapter 1: Calculations Flashcards
How many mL are in 1 quart
1 quart is equal to 2 pints which is equal to 32 oz (1 pint = 16 oz) and there are 30 mL per oz. So 32oz x 30mL = 960 mL
How many grams in 1 pound?
454g = 1 lb
How many mg in 1 grain
65mg = 1 grain
How many quarts in 1 gallon? Convert 1 gallon into mL?
There are 4 quarts in 1 gallon
Each quart = 2 pints. So 4 quarts = 8 pints and since each pint contains 16 oz and there are 30ml in one ounce:
8 x 16 x 30 = 3,840 mL in 1 gallon
How many ounces in 1 cup?
8 oz
How many mcg are in 1 mg?
There are 1,000 mcg in 1 mg
What % of ferrous sulfate contains elemental iron?
Ferrous sulfate (FeSO4) contains 20% elemental iron
Convert aminophylline to theophylline?
Aminophylline to theophylline; multiply by 0.8
Theophylline must have better bioavailability if the conversion from aminophylline involves taking 80% of what was started with for proper theophylline dosing
Likewise, converting from theophylline to aminophylline would obviously require more aminophylline so the conversion requires dividing theophylline qty by 0.8
Convert 0.04% to a ratio strength?
Ratio strengths are displayed as example 1:5000
0.04g/100g = 1part/xparts –> solving for x gives 2500 so 0.04% as a ratio strength = 1:2500
What is the equation for specific gravity (SG)?
SG = g/mL
SG is the ratio of the density of a substance to the density of water. Water has a SG of 1 where 1mL of water = 1 g of water. Substances with SG greater than 1 are heavier than water whereas substances with a SG less than 1 are lighter than water.
What is the formula you would use for dilution and concentration problems?
Ex. How many grams of petrolatum (diluent) should be added to 250g of a 20% ichthammol ointment to make a 7% ichthammol ointment?
Q1 x C1 = Q2 x C2
Ex. 250g x 20% = Xg x 7%
X = 714.3g - 250g (already present) = 464.3g of petrolatum required
Osmolarity is the total number of particles in a given solution and is directly proportional to its osmotic pressure. Identify the number of dissociation particles from each of the following:
Dextrose Mannitol Potassium chloride (KCl) Sodium chloride (NaCl) Sodium acetate (NaC2H3O2) Calcium chloride (CaCl2) Sodium citrate (Na3C6H5O7)
Dextrose 1 Mannitol 1 Potassium chloride (KCl) 2 Sodium chloride (NaCl) 2 Sodium acetate (NaC2H3O2) 2 Calcium chloride (CaCl2) 3 Sodium citrate (Na3C6H5O7) 4
What is the osmolarity calculation formula?
mOsmol/L =
[Wt of substance (g/L) / MW (g/mole)] x # of particles x 1000
Osmolarity is the measure of total number of particles (or solutes) per liter of solution. Solutes can either be ionic (such as NaCl, which dissociates into 2 solutes) or non-ionic, which does not dissociate (such as glucose and urea).
Examples:
KCl dissociates into 2 particles (K+ and Cl-)
CaCl dissociates into 3 particles (Ca+2 and Cl-)
What is the E-value formula?
E = (58.5)(i) / (MW of drug)(1.8)
The “E value” also called sodium chloride equivalent, is the relationship between the amount of drug that produces a particular osmolarity and the amount of sodium chloride that produces the same osmolarity.
An important factor when doing E-value problems is understanding the dissociation factor (i). If the substance consists of only 1 ion, then use 1 for the i value. If it dissociates into 2 ions, add 0.8 to 1 = 1.8 for i value. If it dissociates into 3, add 0.8 to 1.8 = 2.6 and so on.
What are moles measured in? Millimoles?
Moles are measured in g/MW: mols = g/MW
Millimoles measured in mg/MW: mmols = mg/MW