Question

please help me with the calculation. you may need to use the formulas for multiple extravascular administrations

Multiple EVs, 2020)-1 (page 5 of 5) L ® Q Search 5. Ampicillin has the following average pharmacokinetic parameters in a 70 Kg patient: Foral)=0.6; Vd=20L; CL=160 mL/min; Ka=1.5/h Determine if 500 mg/6 h is the correct dosage regimen in order to keep the plasmatic concentration above the minimum effective concentration of 0.39 mg/L (MEC against a microorganism producing the patient's infection). OBSADBOB

this equation list may help you

Answer 1

Ampicillin is eliminated by First order kinetics

Hence,

Dose rate = (Cpss * CLa) / F

where,

• Cpss = target plasma concentration - > 0.39mg/L
• CLa = clearance of ampicillin  
• F = Fraction of Oral drug absorbed -> 0.6

Now, CLa = Vd * Ka = 20 * 1.5 = 30 L/h

Dose rate = (0.39 * 30) / 0.6 = 11.7/0.6 =19.5 mg/hour = 117 mg 6 hourly

Hence, A dosage of 500mg 6 hourly is more than sufficient and can even be reduced to 250mg 6 hourly.

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