Dosage Calculation Practice Questions PDF

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Dosage Calculation Practice Problems

The following questions are very similar to the types of calculations you’ll be asked to perform on the midterm and final exams and your professional practice. Final solutions to all questions have been given in bold. Be sure to work through these calculations along with the pharmacology e-module “Core Concepts in Pharmacology”. ______________________________________________________________________ 1. Navneet, a 75 kg patient, has just undergone surgery and requires an IV infusion of an antibiotic to treat a post-operative infection. The drug monograph gives you the following information: Cl = 2.34 L/hour Vd = 20 L Therapeutic range = 2 mg/L – 5 mg/L What is the half-life of the drug? (Answer: 5.9 h) If the concentration of drug in Navneet’s plasma is measured to be 100 mg/L, what is the concentration of the drug after 4 hours? (Answer: 62.6 mg/L) ______________________________________________________________________ 2. Thom, a 70 kg patient has been prescribed an anti-inflammatory drug with the following information printed on its monograph: Vd = 50 L Half-life (t1/2) = 3 h Therapeutic range = 1 mg/L – 3.5 mg/L What is the dosing interval (Answer: 5.4 h)? What is the maintenance dose of this drug (Answer: 141 mg)? ______________________________________________________________________ 3. Phil weighs 65 kg. He is taking an NSAID with the following properties: Vd = 1.5 L/kg Half-life (t1/2) = 5 h Therapeutic range = 2.6 mg/L – 3.5 mg/L What is the loading dose of the drug (Answer: 341.3 mg)? What is the clearance of the drug (Answer: 13.5 L/hr)?

4. Neena, a 20 kg child, has strep throat and was prescribed an antibiotic drug to treat the infection. The drug monograph gives you the following information: Vd = 0.5 L/kg Half-Life (t1/2) = 2 h Dosage interval = 3 h Therapeutic range = 50 – 150 mg/L Bioavailability = 70% What is the loading dose for this antibiotic (Answer: 2142.9 mg)? What is the maintenance dose (Answer: 1485 mg)? ***Please note that the bioavailability of this drug is not 100%. As such, this factor must be taken into consideration when calculating the loading and maintenance dose of this drug*** Hint: Divide both the loading dose and maintenance dose by the bioavailability of the drug (70% = 0.7). ______________________________________________________________________ 5. Your patient is a 50 kg female being treated with an anti-hypertensive medication. The volume of distribution for the drug is 1.8 L/kg, the half-life is 2 hours, and the therapeutic range of is 1 - 3 mg/L. The bioavailability of the drug is 50%. Calculate the loading dose (Answer: 540 mg). ______________________________________________________________________ 6. Justin is 70 kg. He is taking an antidepressant drug to manage depressive symptoms. The following information printed in the drug monograph: Vd = 50L Half-life (t1/2) = 10 hours Therapeutic range = 1.5 - 4.5 mg/L. Calculate drug clearance (Answer: 3.465 L/hr) and determine the dose that would be administered every 24 hours (Answer: 249.48 mg). The bioavailability of the drug is 100%.

7. Drug A has a half-life of 3 hours, a volume of distribution of 30 L, and a therapeutic range of 2 - 5 mg/L. Calculate the maintenance dose (Answer: 96.22786355 mg) and the dose interval (Answer: 3.967341313 hr). Assume that the bioavailability of the drug is 100%. ______________________________________________________________________ 8. The anti-depressant drug Elevate has a therapeutic range of 2 - 6 mg/L and a half-life of 12 hours. If the plasma concentration of the drug is 4 mg/L at the start of measurement, what will the concentration of the drug be in 5 hours (Answer: 2.996953829 mg/L) and how long will it take for the drug to reach a steady state in the plasma (Answer: 48 hr)? ______________________________________________________________________ 9. A drug has a clearance of 15 L/hr. The therapeutic concentration is 5 mg/L. In order to maintain the therapeutic effect, the drug is administered every 10 hours. The bioavailability of this drug is 25%. Calculate the appropriate maintenance dose for the patient (Answer: 3000 mg)....