Formulas Flashcards
1 tsp
5 mL
1 tbsp
15 mL
1 fl oz
30 mL
1 cup
8 oz (240 mL)
1 pint
2 cups (480 mL)
1 quart
2 pints (960 mL)
1 gallon
4 quarts (3840 mL)
1 kg
2.2 pounds
1 oz
28.4 grams
1 pound
454 grams (16 oz)
1 grain
65 mg
1 inch
2.54 cm
Specific Gravity (SG)
SG = g/mL
Q1C1 (Dilution and Concentration)
Q1C1 = Q2C2
Units must match
Osmolarity
mOsm/L = [wt of substance (g/L) / MW (g/mole)] x # of particles x 1,000
just mOsm: the weight isn’t normalized to per liter
Dissociation Factor
1 ion: i = 1
2 ions: i = 1.8
3 ions: i = 2.6
4 ions: i = 3.4
5 ions: i = 4.2
E value
Sodium chloride equivalent
E = [58.5 x i] / [MW x 1.8]
mols
g/MW
mmols = mg/MW
mEq
(mg x valence) / MW
OR
mmol x valence
Fluid Needs
1,500 mL + (20mL)(wt in kg - 20)
Calories from Macronutrients
Dextrose = 3.4 kcal
Protein = 4 kcal
Lipids = 10% - 1.1kcal/mL, 20% - 2kcal/mL, 30% - 3kcal/mL
TEE
BBE x activity factor x stress factor
Nitrogen intake
grams of protein / 6.25
IBW
male = 50 + 2.3(inches of height over 60)
female = 4.5 + 2.3(inches of height over 60)
AdjBW
IBW + (0.4)(TBW-IBW)
Drugs that use IBW for dosing
theophylline/aminophylline, acyclovir, levothyroxine
Drugs that use AdjBW when obese
aminoglycosides
Cockcroft-Gault Equation
CrCl = [(140-Age) / (72 x Scr)] x wt in kg ( x 0.85 if female)
TBW <IBW = TBW
BMI <25 = IBW
BMI >25 = AdjBW
Weak Acid pH formula
pH = pKa + log[salt/acid]
Weak Base pH formula
pH = pKa + log[base/salt]
Weak Acid % Ionization
% ionization = 100 / (1 + 10^(pKa - pH))
Weak Base % Ionization
% ionization = 100 / (1 + 10^(pH - pKa))
Aminophylline to Theophylline
Multiply by 0.8
A T M
Theophylline to Aminophylline
Divide by 0.8
Absolute Neutrophil Count
ANC = WBC x [(segs+bands)/100]
segs = neutrophils
Fahrenheit to Celsius
C = (F - 32) / 1.8
Celsius to Fahrenheit
F = (1.8 x C) + 32
LDL
LDL = TC - HDL - (TG/5)
Only can be used if TG <400
Bioavailability
F = 100 x [AUCex/AUCiv] x [DOSEiv/DOSEex]
Volume of Distribution
Vd = amt of drug in body / concentration of drug in plasma
Clearance
Cl = (F x dose) / AUC
Cl = Vd x ke
Elimination Rate Constant
ke = Cl/Vd
Half Life
t1/2 = 0.693/ke
Loading Dose
LD = (Desired Concentration x Vd) / F
Predicting Drug Concentrations
C2 = C1 x e^(-kt)
ke = ln (C1/C2) / t
KCl solution to tablet
10% = 20 mEq/15 mL
Calcium Elemental
Calcium citrate = 21% elemental calcium
Calcium carbonate = 40% elemental calcium
Statin Equivalent Doses
Pitavastatin = 2 mg
Rosuvastatin = 5 mg
Atorvastatin = 10 mg
Simvastatin = 20 mg
Lovastatin = 40 mg
Pravastatin = 40 mg
Fluvastatin = 80 mg
IV to PO ratios
Metoprolol = 1:2.5
Levothyroxine = 0.75:1
Furosemide = 1:2
Loop Diuretic Equivalent Doses
Bumetanide = 1 mg
Torsemide = 20 mg
Furosemide = 40 mg
Ethacrynic Acid = 50 mg
Iron Elemental
Ferrous Sulfate = 20% elemental iron
Insulin Conversions
NPH BID -> Insulin glargine QD = 80% of NPH dose
Toujeo -> Lantus, Basaglar, Detemir = 80% of Toujeo dose
Steroids Equivalent Doses
Cortisone = 25 mg
Hydrocortisone = 20 mg
Prednisone = 5 mg
Prenisolone = 5 mg
Methylprednisolone = 4 mg
Triamcinolone = 4 mg
Dexamethasone = 0.75 mg
Betamethasone = 0.6 mg
Lithium Conversion
5 mL = 8 mEq = 300 mg
Risk
Risk = # of pts with unfavorable event / # of pts in group
Relative Risk
RR = Risk of Treatment Group / Risk of Control Group
Relative Risk Reduction
RRR = 1 - RR(in decimal form)
Absolute Risk Reduction
ARR = Risk of Control Group - Risk of Treatment Group
Number Needed to Treat/ Number Needed to Harm
NNT or NNH = 1/ARR
Round up in NNT
Round down in NNH
Odds Ratio
OR = AD/BC
Chart is arranged:
A B
C D
Hazard Ratio
HR = Hazard Rate in Treatment Group / Hazard Rate in Control Group
(Same as RR)
Incremental Cost Ratio
(C2-C1) / (E2-E1)
