7220 Practice Problems

A patient receives digoxin 250 mcg daily as a tablet at home but has an NG tube placed. Calculate an equivalent dose of digoxin elixir to administer via NG tube.

Digoxin Tablet F = 0.7
Digoxin Elixir F = 0.8
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Patient is at steady state on a drug regimen. The first plasma drug concentration is obtained at 10 AM, four hours after his daily dose. Sixteen hours after his daily dose, another plasma drug concentration is obtained.

C₁ = 15.6 mg/dL
C₂ = 12.3 mg/dL

Calculate the patient's elimination constant. Use the elimination constant calculated to calculate half-life (t1⁄2)
Calculate percentage of steady state achieved at 5 hours if the elimination constant is 0.451 hr-1.fraction of steady state at time, t = 1 - e^-kt x = 1 - e^(-0.451x5) x = 89.5%32 yo M Ht: 6' 4" Wt: 255 lb SCr: 1.4 Calculate the patient's creatinine clearance using CG equation.BMI = (255/2.2)/(76 x 2.54/100)² = 31.1 → use Adjusted Body Weight IBW = 50 + (2.3 x 16) = 86.8 kg AdjBW = 86.8 + 0.4(115.9 - 86.8) = 98.4 CrCl = [(140-32) x 98.4 kg]/(72 x 1.4) = 105 mL/minDrug X is 67% metabolized and 33% renally cleared. Normal Dose: 500 mg q8h 1. Calculate the adjusted dose factor for 25% residual renal function. 2. Recommend a dosing regimen for the patient using adjusted dosing factor.0.67 + (0.25 x 0.33) = 0.75 0.75 x 1500 mg/day = 1125 mg daily 375 mg q8h is a practical dosing regimen.45 yo F Ht: 5'8" Wt: 132 lbs SCr: 0.9 Calculate creatinine clearance using CG equation.BMI = (132/2.2)/(68 x 2.54 /100)² = 20 kg/m² → use ABW IBW = 45 + (2.3 x 8) = 63.4 kg [(140 - 45) x 20.3 kg]/(72 x 0.9) = 92.95 x 0.85 (patient is female) = 26 mL/min65 yo M Ht: 5'6" Wt: 275 lbs SCr: 1.3 Calculate creatinine clearance using CG equation.BMI = (275/2.2)/(66 x 2.54 / 100)² = 44.5 kg/m² IBW = 50 + (2.3 x 6) = 63.8 kg LBW =. (9270 x 125 kg)/(6680 + 216 x 44.5 kg/m²) = 71.14 kg [(140 - 65).x 71.14 kg]/(72 x 1.3) = 57 mL/min27 yo F Ht: 5'6" Wt: 188 lbs SCr: 1.2 Calculate creatinine clearance using CG equation.BMI = (188/2.2)/(66 x 2.54 / 100)² = 30.4 kg/m² IBW = 45 + (2.3 x 6) = 58.8 kg AdjBW = 58.8 + 0.4(85.5 - 58.8) = 69.5 kg [(140 - 27) x 69.5]/(72 x 1.2) = 90.9 x 0.85 = 77.3 = 77 mL/min42 yo M with sepsis SCR: 1.4 mg/dL at admission CrCl: 74 mL/min at admission Day 5: SCr past three days = 2.3 mg/dL Estimate creatinine clearance based on new SCr.New CrCl = (74 mL/min) x (1.4 mg/dL / 2.3 mg/dL) = 45 mL/minPatient is taking 300 mg of a medication q6h that is 35% metabolically cleared. After a course of antibiotics, the patient's renal clearance has declined by 33%. 1. Calculate a new dose adjustment factor. 2. Recommend a new dosing regimen.0.35 + (0.67 x 0.65) = 0.7855 0.7855 x 1200 mg = 942.6 mg daily 900 mg daily would be a practical dosing regimen.Calculate the Vdig for a 68 yo F Ht: 5'8" Wt: 202 lbs SCr: 2.3 mg/dLCalculate the Vdig for a 68 yo F with hypothyroidism Ht: 5'8" Wt: 202 lbs SCr: 2.3 mg/dLCalculate the Cldig for a 68 yo non-CHF F Ht: 5'8" Wt: 202 lbs SCr: 2.3 mg/dLCalculate the Cldig for a 68 yo non-CHF F with hypothyroidism taking verapamil Ht: 5'8" Wt: 202 lbs SCr: 2.3 mg/dL