RxPrep - Required Formulas
Steroid Conversions - cortisone - hydrocortisone - prednisone - prednisolone - methylprednisolone - triamcinolone - dexamethasone - betamethasone
- cortisone - 25 mg - hydrocortisone - 20 mg - prednisone - 5 mg - prednisolone - 5 mg - methylprednisolone - 4 mg - triamcinolone - 4 mg - dexamethasone - 0.75 mg - betamethasone - 0.6 mg
acidosis - pH? - pCO2? - HCO3?
- pH <7.35 - pCO2 >45 - HCO3 <22
alkalosis - pH? - pCO2? - HCO3?
- pH >7.45 - pCO2 <35 - HCO3 >26
ke = ...
ke = (ln (C1 / C2)) / t
Elimination Rate Constant (ke)
ke = Cl / Vd
Milliequivalents (mEq)
mEq = mmols * valence OR mEq = [mg * valence] / MW
Osmolarity Equation
mOsmol/L = [weight (g/L) / MW (g/mole)] * (# of particles) * 1000
To convert aminophylline to theophylline...
"ATM" MULTIPLY by 0.8
To convert theophylline to aminophylline...
"ATM" DIVIDE by 0.8
Percent Ionization - Weak Base
% ionization = 100 / 1 + 10^(pH-pKa)
Percent Ionization - Weak Acid
% ionization = 100 / 1 + 10^(pKa-pH)
Statin Conversions - pitavastatin - rosuvastatin - atorvastatin - simvastatin - lovastatin - pravastatin - fluvastatin
- pitavastatin - 2 mg - rosuvastatin - 5 mg - atorvastatin - 10 mg - simvastatin - 20 mg - lovastatin - 40 mg - pravastatin - 40 mg - fluvastatin - 80 mg
NNT or NNH
1 / ARR
Initiating Basal-Bolus in Type 1 Diabetes - NPH/regular?
1) TDD - 0.6 units/kg/day using TBW 2) Divide 1/2 basal & 1/2 bolus OR 2) Divide 2/3 NPH & 1/3 regular 3) split rapid acting among meals
1 tbsp
15 ml
Correction Factor - regular insulin?
1500 Rule correction factor for 1 unit = 1500 / TDD
ILE 10% (kcal/mL?)
1.1 kcal/mL
1 meter
100 cm
1 pint - oz? - ml?
16 ounces 480 ml (473 ml actual)
Correction Factor - rapid-acting insulin?
1800 Rule correction factor for 1 unit = 1800 / TDD
furosemide IV:PO conversion ratio
1:2
ILE 20% (kcal/ml?)
2 kcal/ml
1 quart - pints? - ml?
2 pints 960 ml (946 ml actual)
1 kg
2.2 lb
1 inch
2.54 cm
KCl 10% --> ___ mEq/ml
20 mEq / 15 ml
ferrous sulfate - elemental iron?
20%
Calcium Citrate (Citracal) - % elemental calcium
21%
1 oz - grams?
28.4 grams
ILE 30% (kcal/mL?)
3 kcal/ml
Dextrose (kcal/gram?)
3.4 kcal/g
1 fl oz
30 ml (29.57 ml actual)
Amino Acids (kcal/gram?)
4 kcal/g
Carbs (kcal/g?)
4 kcal/g
Protein (kcal/g?)
4 kcal/g
1 gallon - quarts? - ml?
4 quarts 3840 ml (3785 ml actual)
KCl 20% --> ___ mEq/ml
40 mEq / 15 ml
Calcium Carbonate (TUMS) - % elemental calcium
40%
1 lb - grams?
454 grams
1 tsp
5 ml
1 grain - mg?
65 mg
1 cup - oz? - ml?
8 ounces 240 ml (236.56 ml actual)
Fats (kcal/g?)
9 kcal/g
Dehydration (BUN:SCr?)
>20:1 ratio
Adjusted Body Weight (ABW)
ABW = IBW + 0.4*(TBW-IBW)
Anion Gap
AG = Na - Cl - HCO3
Absolute Neutrophil Count (ANC)
ANC = WBC * [(% segs + % bands) / 100]
Absolute Risk Reduction (ARR)
ARR = (% risk control) - (% risk treatment)
aminoglycosides - weight to use?
Adj BW
BMI equation
BMI = weight (kg) / [height (m)]^2 or BMI = (weight (lb) / [height (in)]^2) * 703
BSA Calculation (Mostellar)
BSA (m2) = Sqrt [(height cm * weight kg) / 3600]
Fahrenheit to Celsius
C = (F-32) / 1.8
C2 = ...
C2 = C1 * e^-k*t
Sensitivity
COLUMNS
Clearance (Cl)
Cl = (F*Dose) / AUC or Cl = ke * Vd
Corrected Ca
Corrected Ca = Ca + [(4 - albumin) * 0.8]
Corrected Phenytoin
Corrected for low albumin (<3.5): Corrected Phenytoin = total phenytoin measured / [(0.2 * albumin) + 0.1] *also used for valproic acid
Correction Dose Equation
Correction Dose = (BG now - target BG) / correction factor
Isotonicity (E Value)
E = [58.5 * i] / [MW * 1.8]
Bioavailability (F)
F (%) = 100 * [AUC PO / AUC IV] * [Dose IV / Dose PO]
Celsius to Fahrenheit
F = (C*1.8) + 32
Hazard Ratio (HR)
HR = HR in treatment / HR in control group
Acyclovir - weight to use?
IBW
aminophylline - weight to use?
IBW
levothyroxine - weight to use?
IBW
theophylline - weight to use?
IBW (even if obese)
metoprolol IV:PO conversion ratio
IV:PO - 1:2.5
Loading Dose Equation
LD = (Desired Conc. * VD) / F
Dyslipidemia (LDL) Equation
LDL = TC - HDL - (TG / 5) *do NOT use if TG >400
Opioid Conversions - morphine (IV/PO) - hydromorphone (IV/PO) - oxycodone (___; PO)
Morphine [ 10 (IV) - 30 (PO)] Hydromorphone [1.5 (IV) - 7.5 (PO)] Oxycodone [ ___ (IV) - 20 (PO)]
Grams of Nitrogen from Protein
Nitrogen (g) = [protein intake (g)] / 6.25
Odds Ratio (OR)
OR = AD / BC Outcomes- columns Present/absent - rows
Dilution and Concentration Equation
Q1*C1 = Q2*C2
Specificity
ROWS
Relative Risk (RR)
RR = risk in treatment group / risk in control group
Relative Risk Reduction (RRR)
RRR = (% risk control - % risk treatment) / % risk control group
Risk
Risk = # subjects with event / total # of subjects in group
Insulin-to-Carb Ratio - regular insulin?
Rule of 450 g of carbs covered by 1 unit insulin = 450 / TDD
Insulin-to-Carb Ratio - Rapid-acting insulin?
Rule of 500 g of carbs covered by 1 unit insulin = 500 / TDD
Specific Gravity (SG)
SG = g / ml SG = weight (g) / g or ml of equal volume of water
Total Energy Expenditure (TEE)
TEE = BEE x activity factor x stress factor
Time to Burn (TTB)
TTB (with sunscreen; minutes) = SPF * TTB (without sunscreen)
NPH dosed BID --> glargine daily
Use 80% of NPH MULTIPLY by 0.8
Minimum Weighable Quantity (MWQ)
Used for Torsion Scale MWQ = Sensitivity Requirement (SR) / 0.05
Volume of Distribution (Vd)
Vd = amount of drug in body / concentration of drug in plasma Vd = D / C
Fluid Needs Equation?
When weight >20 kg: 1500 ml + (20 ml)*(weight (kg) - 20)
Loop Diuretics Conversions - bumetanide - torsemide - furosemide - ethacrynic acid
bumetanide - 1 mg torsemide - 20 mg furosemide - 40 mg ethacrynic acid - 50 mg
Millimoles equation
mmols = mg / MW
Moles equation
mols = g / MW
Weak Base pH Calculation
pH = pKa + log (base/salt)
Weak Acid pH Calculation
pH = pKa + log (salt/acid)
ratio strength
ratio strength = 100 / percentage strength
Alligation
refer to sheet
Half-Life Equation
t 1/2 = 0.693 / ke
Toujeo --> Lantus or Basaglar
use 80% of Toujeo DIVIDE by 0.8