Required Formulas for Calculations Flashcards
1 quart = X mL
960 mL
1 gallon = X mL
3,840 mL
1 pound = X g
454 g
1 grain = X mg
65 mg
Specific Gravity equation
SG = g/mL
PPM –> % strength
move decimal left 4 places
% strength –> PPM
move decimal right 4 places
Osmolarity equation
mOsm/L = [wt of substance (g/L)] / [MW (g/mole)] x (# of particles) x 1000
Isotonicity equation (E value)
E = [(58.5 x i) / (MW of drug x 1.8)]
moles equation
mols = g/MW
mmols equation
mmols = mg/MW
mEq equation
mEq = [ (mg x valence) / MW ] or
mEq = mmols x valence
Enteral Nutrition Calories
Carbs/Protein = 4 kcal/g Fat = 9 kcal/g
Parenteral Nutrition Calories
Dextrosee monohydrate = 3.4 kcal/g Amino acid solutions = 4 kcal/g ILE 10% = 1.1 kcal/mL ILE 20% = 2 kcal/mL ILE 30% = 3 kcal/mL
Ideal Body Weight equation
IBW.m = 50 kg + 2.3 (>5’)
IBW.f = 45.5 kg + 2.3 (>5’)
Adjusted Body Weight equation
AdjBW = IBW + 0.4(TBW - IBW)
Which drugs uses IBW for drug dosing?
Aminophylline, Theophylline, Acyclovir & Levothyroxine
Which drugs uses TBW for drug dosing?
LMWH, UFH, and Vancomycin
Which drug uses AdjBW when patients are obese?
Aminoglycosides
Labs that determines dehydration
BUN:SCR > 20:1
ABG: pH/pCO2/pO2/HCO3/O2 sat
pH < 7.35 = alkalosis | pH > 7.45 = acidosis
Respiratory: pCO2 < 35 = alk | > 45 = acidosis
Metabolic: HCO3 > 26 = alk | < 22 = acidosis
if both pCO2 and HCO3 are abnormal; use the one that matches pH
Anion Gap equation
AG = Na - Cl - HCO3
Weak acid equation
pH = pKa + log [salt/acid]
Weak base equation
pH = pKw - pKb + log [base/salt]
Temperature Conversion; C –> F
C = (F - 32) / 1.8
Temperature Conversion: F –> C
F = (C x 1.8) + 32
Absolute Neutrophil Count
ANC = WBC x [ (segs % + bands %) / 100]
segs% or PMN or polys
Risk equation
Risk = [# of subjects in group with an unfavorable event] /
[total # of subjects in group]
Relative Risk equation
RR = [Risk in treatment group] / [Risk in contol group]
Relative Risk Reduction equation
RRR = [ (% risk in control group - % risk in treatment group) / (% risk in control group) ]
Absolute Risk Reduction equation
ARR = (% risk in control group) - (% risk in treatment group)
Number Needed to Treat or Harm equation
NNT or NNH = 1 / ARR
Odds Ratio equation
OR = AD / BC
Exposure - Outcome Present - Outcome Absent
Present A B
Absent C D
Hazard Ratio equation
HR = [Hazard rate in the treatment group] / [Hazard rate in the control group]
Incremental Cost-Effectiveness Ratio equation
ICR = (C2 - C1) / (E2 - E1)
C = costs; E = effects
Pack-Year Smoking History
Pack-Year Smoking History = [Cigarette pack / day] x years smoked
Friedewald Equation for Dyslipidemia
LDL = TC - HDL - [TG* / 5]
*do not use if TG > 400
Volume of Distribution equation
Vd = [amount of drug in body] / [conc of drug in plasma]
Clearance equation PK
Cl = [F x dose] / AUC or Cl = ke x Vd
Elimination Rate Constant (ke)
ke = Cl / Vd
Half-life equation
t(1/2) = 0.693 / ke
Loading Dose equation PK
LD = [desired conc x Vd] / F
Bioavailability (F) equation
F (%) = 100 x [AUC extra / AUC intra] x [Dose IV / Dose EV]
Prediction Drug Concentration equation
C2 = C1 x e^-kt
ke = [ln (C1/C2) / t]
KCL solution oral to tablets
KCl 10% = 20 mEq/15 mL
Calcium Salts conversion
Calcium Carbonate = 40 % elemental calcium
Calcium Citrate = 21 % elemental calcium
Aminophyllin to Theophylline conversion
ATM: A = T x 0.8
**T = A / 0.8
Loop Diuretic Conversions
Ethacrynic acid 50 mg = Furosemide 40 mg = Torsemide 20 mg = Bumetanide 1 mg
Furosemide IV:PO = 1:2
Other Loops IV:PO = 1:1
Metoprolol IV:PO
1:2.5
Ferrous Sulfate conversion
Ferrous Sulfate = 20 % elemental iron (325 mg x 20% = 65 mg iron)
Levothyroxine IV:PO
0.75:1
Steroids Conversions
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
Statin Conversions
Pitavastatin 2 mg Rosuvastatin 5 mg Atorvastatin 10 mg Simvastatin 20 mg Lovastatin 40 mg Pravastatin 40 mg Fluvastatin 80 mg
Lithium Conversions
5 mL lithium citrate syrup = 300mg lithium carbonate = 8 mEq Li* ion
