| Useful Pharmacy Formulas | ||||||||||
| Formula Name | Formula | |||||||||
| Absolute Neutrophil Count (ANC) | ANC = WBC X Percent of neutrophils | |||||||||
| Aminoglycoside Pharmacokinetics | VD = 0.25 X IBW (unless ABW > 25% of IBW), then use VD = 0.25 X (IBW + 0.4 X (ABW - IBW)); Cl = CrCl; Ke = Cl / VD | |||||||||
| Expected level = ((S)(F) dose / VD / 1 - e-(kT)) X e -(kt) | ||||||||||
| T = dosing interval, t = time (for peak t = 1; for trough t = T) | ||||||||||
| Body Mass Index (BMI) | Weight (lbs) X 703 / height (inches) | |||||||||
| Acceptable: < 25; Overweight: 25-29; Obese => 30 | ||||||||||
| Body Surface Area (BSA) | BSA (m2) = (Height (inches) X Weight (lbs) / 3131) 1/2 | |||||||||
| Centimeters to Inches (Height) | Height (inches) = Height (cm) / 2.54 | |||||||||
| Creatinine Clearance (CrCl) | CrCl = (140 - age X IBW (kg)) / (72 X SCr) | |||||||||
| for females: multiply above by 0.85 | ||||||||||
| Corrected Albumin (for Phenytoin levels) | Corrected level = Phenytoin level / 0.2 X (Albumin + 0.1) | |||||||||
| Digibind Dosing | Dose (vials) = serum digoxin (ng/ml) X weight (kg) / 100 | |||||||||
| Each vial contains 38mg and binds to approximately 0.5mg of digoxin; dispense with 0.22 micron filter and dilute in 50-100 normal saline | ||||||||||
| Digoxin Pharmacokinetics | VD = (3.8 X IBW) + (3.1 X CrCl); Cl = (0.8 X IBW) + CrCl; Ke = Cl / VD | |||||||||
| Expected level = (S)(F) dose / dosing interval / Cl | ||||||||||
| (S = 1; F = 0.7 for tablet, 0.8 for elixir, and 1 for capsule and IV) | ||||||||||
| Ideal Body Weight (IBW) | Male: 106 lbs for first 5 feet, then 6 lbs for each inch over 5 feet | |||||||||
| Female: 100 lbs for first 5 feet, then 5 lbs for each inch over 5 feet | ||||||||||
| OR | ||||||||||
| Adults (18 y/o+): IBW (male) (kg) = 50 + (2.3 X height in inches over 5 feet) | ||||||||||
| IBW (female) (kg) = 45.5 + (2.3 X height in inches over 5 feet) | ||||||||||
| Children (IBW is in kg, height in cm) | ||||||||||
| 1-18 y/o: IBW = (height2 X 1.65) X 1000 | ||||||||||
| 5 feet and taller: IBW (male) = 39 + (2.27 X height in inches over 5 feet) | ||||||||||
| IBW (female) = 42.2 + (2.27 X height in inches over 5 feet) | ||||||||||
| Phenytoin Pharmacokinetics | VD = 0.65 X ABW; Vm = 7 X ABW; Km = 4 | |||||||||
| Expected level = 4 X (S)(F) dose / Vm - dose | ||||||||||
| Valproic Acid Pharmacokinetics | VD = 0.14 X IBW; Cl (children) = 13 ml/kg/hr; Cl (adults) = 8 ml/kg/hr | |||||||||
| Expected level = ((S)(F) dose / VD / 1 - e-(kT)) X e -(kt) | ||||||||||
| Vancomycin Pharmacokinetics | VD = 0.7 X ABW; Cl = CrCl; Ke = Cl / VD | |||||||||
| Expected level = ((S)(F) dose / VD / 1 - e-(kT)) X e -(kt) | ||||||||||
| (T = dosing interval, t = time (for peak t = 2; for trough t = T) | ||||||||||
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