Dosage Calculations - Pharmacy Technician Certification Exam Ptce

1. A patient is to receive 1.5 L of an IV fluid over 24 hours. What should the flow rate be set to in mL/hr?
   Answer: 62.5 mL/hr The correct answer is 62.5 mL/hr. First, convert the volume from liters to milliliters: $1.5\ \text{L} = 1500\ \text{mL}$. Then, divide the total volume by the total time in hours: $1500\ \text{mL} \div 24\ \text{hours} = 62.5\ \text{mL/hr}$.
2. A prescription for an oral solution with a concentration of 50 mg/5 mL is written with the sig "Take 10 mL twice daily." How many milligrams (mg) of the drug will the patient take each day?
   Answer: 200 mg The correct answer is 200 mg. First, determine the strength per mL: $50\ \text{mg} \div 5\ \text{mL} = 10\ \text{mg/mL}$. Next, calculate the amount per dose: $10\ \text{mL/dose} \times 10\ \text{mg/mL} = 100\ \text{mg/dose}$. Finally, calculate the total daily dose: $100\ \text{mg/dose} \times 2\ \text{doses/day} = 200\ \text{mg/day}$.
3. A prescription for an oral liquid has the sig: "i tbsp po tid." What is the total volume in mL that the patient will take each day? (1 tbsp = 15 mL)
   Answer: 45 mL The correct answer is 45 mL. The sig code "i tbsp" means one tablespoon, which is 15 mL. The sig code "tid" means three times a day. Therefore, the total daily volume is $15\ \text{mL/dose} \times 3\ \text{doses/day} = 45\ \text{mL/day}$.
4. A patient receives a Z-Pak, which contains azithromycin 250 mg tablets. The instructions are to take 500 mg on Day 1, then 250 mg once daily on Days 2 through 5. What is the total amount of azithromycin in grams (g) taken during the entire course of therapy?
   Answer: 1.5 g The correct answer is 1.5 g. Calculate the total mg taken: Day 1 is 500 mg. Days 2-5 is 4 days, so $4 \times 250\ \text{mg} = 1000\ \text{mg}$. The total course is $500\ \text{mg} + 1000\ \text{mg} = 1500\ \text{mg}$. Convert mg to g: $1500\ \text{mg} \div 1000\ \text{mg/g} = 1.5\ \text{g}$.
5. An adult patient who weighs 176 lbs needs a one-time dose of a drug at 5 mg/kg. How many milligrams (mg) should the patient receive? (Use the conversion 1 kg = 2.2 lbs)
   Answer: 400 mg The correct answer is 400 mg. First, convert the patient's weight from pounds to kilograms: $176\ \text{lbs} \div 2.2\ \text{lbs/kg} = 80\ \text{kg}$. Then, calculate the dose: $80\ \text{kg} \times 5\ \text{mg/kg} = 400\ \text{mg}$.
6. A patient is prescribed 600 mg of a medication to be taken three times daily. What is the total daily dose in grams (g)?
   Answer: 1.8 g The correct answer is 1.8 g. First, calculate the total daily dose in milligrams: $600\ \text{mg/dose} \times 3\ \text{doses/day} = 1800\ \text{mg/day}$. Then, convert milligrams to grams: $1800\ \text{mg} \div 1000\ \text{mg/g} = 1.8\ \text{g}$.
7. A 500 mL IV bag is infused at a rate of 75 mL/hr. How long will it take for the entire bag to be infused?
   Answer: 6.7 hours The correct answer is 6.7 hours. To find the infusion time, divide the total volume by the infusion rate: $500\ \text{mL} \div 75\ \text{mL/hr} \approx 6.67\ \text{hours}$, which rounds to 6.7 hours.
8. A prescription for prednisone 5 mg tablets has the following directions: "Take 4 tabs daily for 2 days, then 3 tabs daily for 2 days, then 2 tabs daily for 2 days, then 1 tab daily for 2 days." What is the total number of tablets to dispense?
   Answer: 20 tablets The correct answer is 20 tablets. Calculate the number of tablets for each step of the taper and add them together: $(4 \times 2) + (3 \times 2) + (2 \times 2) + (1 \times 2) = 8 + 6 + 4 + 2 = 20\ \text{tablets}$.
9. A prescription for an oral suspension requires a dose of 400 mg. The pharmacy has a stock bottle with a concentration of 250 mg/5 mL. How many milliliters (mL) should be administered for each dose?
   Answer: 8 mL The correct answer is 8 mL. Using ratio and proportion: $\frac{250\ \text{mg}}{5\ \text{mL}} = \frac{400\ \text{mg}}{x\ \text{mL}}$. Cross-multiply: $250x = 2000$. Solve for x: $x = 2000 \div 250 = 8\ \text{mL}$.
10. How many grams of sodium chloride are needed to prepare 1 liter of 0.9% normal saline solution?
    Answer: 9 g The correct answer is 9 g. A 0.9% solution means there are 0.9 grams of solute per 100 mL of solution. First, convert 1 liter to 1000 mL. Then, set up a proportion: $\frac{0.9\ \text{g}}{100\ \text{mL}} = \frac{x\ \text{g}}{1000\ \text{mL}}$. Cross-multiply: $100x = 900$. Solve for x: $x = 9\ \text{g}$.
11. A pediatric patient weighing 18 kg is prescribed a medication with a dosing schedule of 10 mg/kg/day, to be given in two divided doses. How many milligrams (mg) should be administered in a single dose?
    Answer: 90 mg The correct answer is 90 mg. First, calculate the total daily dose: $18\ \text{kg} \times 10\ \text{mg/kg/day} = 180\ \text{mg/day}$. Since the total daily dose is divided into two doses, divide by 2: $180\ \text{mg} \div 2 = 90\ \text{mg/dose}$.
12. A pharmacist prepares an IV admixture by adding 4 g of a medication to a 500 mL bag of D5W. What is the final concentration of the medication in mg/mL?
    Answer: 8 mg/mL The correct answer is 8 mg/mL. First, convert grams to milligrams: $4\ \text{g} = 4000\ \text{mg}$. Then, divide the total milligrams of the drug by the total volume in milliliters: $4000\ \text{mg} \div 500\ \text{mL} = 8\ \text{mg/mL}$.
13. A physician prescribes amoxicillin 750 mg. The pharmacy has 250 mg tablets in stock. How many tablets should the patient take for one dose?
    Answer: 3 tablets The correct answer is 3 tablets. To find the number of tablets per dose, divide the prescribed dose by the strength of the available tablets. Calculation: $750\ \text{mg} \div 250\ \text{mg/tablet} = 3\ \text{tablets}$.
14. An IV order specifies that 1 liter of 0.9% sodium chloride should be infused over 10 hours. What is the correct flow rate in mL/hr?
    Answer: 100 mL/hr The correct answer is 100 mL/hr. First, convert liters to milliliters: $1\ \text{L} = 1000\ \text{mL}$. Then, divide the total volume by the total time in hours: $1000\ \text{mL} \div 10\ \text{hours} = 100\ \text{mL/hr}$.
15. A pharmacy technician needs to prepare 240 g of a 2.5% ointment. The technician will use a 1% ointment and a 5% ointment. How many grams of the 5% ointment are needed?
    Answer: 90 g The correct answer is 90 g. This problem can be solved using alligation. The difference between the desired strength (2.5%) and the lower strength (1%) is 1.5. This means 1.5 parts of the higher strength are needed. The difference between the higher strength (5%) and the desired strength (2.5%) is 2.5. This means 2.5 parts of the lower strength are needed. The total number of parts is $1.5 + 2.5 = 4$. The proportion of the 5% ointment needed is $\frac{1.5}{4}$. Calculate the amount: $\frac{1.5}{4} \times 240\ \text{g} = 90\ \text{g}$.
16. A technician needs to prepare 1 liter of a 10% solution from a 50% stock solution. How many milliliters (mL) of the stock solution are required?
    Answer: 200 mL The correct answer is 200 mL. This is a dilution problem that can be solved using the formula $C_1V_1 = C_2V_2$. $C_1 = 50\%$, $V_1 = ?$, $C_2 = 10\%$, $V_2 = 1\ \text{L} = 1000\ \text{mL}$. So, $(50\%) \times V_1 = (10\%) \times (1000\ \text{mL})$. $V_1 = (10 \times 1000) \div 50 = 200\ \text{mL}$.
17. An IV bag contains 40 mEq of potassium chloride (KCl) in 1000 mL of fluid. If the IV is administered to the patient at a rate of 125 mL/hr, how many mEq of KCl is the patient receiving per hour?
    Answer: 5 mEq The correct answer is 5 mEq. First, find the concentration of KCl in mEq/mL: $40\ \text{mEq} \div 1000\ \text{mL} = 0.04\ \text{mEq/mL}$. Then, multiply the concentration by the infusion rate: $0.04\ \text{mEq/mL} \times 125\ \text{mL/hr} = 5\ \text{mEq/hr}$.
18. A patient is prescribed an inhaler containing 120 metered doses. The instructions are to take 2 puffs in the morning and 2 puffs in the evening. How many days will this inhaler last?
    Answer: 30 days The correct answer is 30 days. First, calculate the total puffs per day: $2\ \text{puffs} + 2\ \text{puffs} = 4\ \text{puffs/day}$. Then, divide the total doses in the inhaler by the daily usage: $120\ \text{doses} \div 4\ \text{doses/day} = 30\ \text{days}$.
19. A patient is to take 7.5 mL of an oral solution twice a day for 14 days. What is the total volume in mL that should be dispensed?
    Answer: 210 mL The correct answer is 210 mL. First, calculate the total daily volume: $7.5\ \text{mL/dose} \times 2\ \text{doses/day} = 15\ \text{mL/day}$. Then, multiply the daily volume by the duration of therapy: $15\ \text{mL/day} \times 14\ \text{days} = 210\ \text{mL}$.
20. A vial of antibiotic powder must be reconstituted to a final concentration of 250 mg/mL. If a dose of 800 mg is required, how many milliliters (mL) should be drawn into the syringe?
    Answer: 3.2 mL The correct answer is 3.2 mL. To find the volume needed, divide the desired dose by the concentration of the solution. Calculation: $800\ \text{mg} \div 250\ \text{mg/mL} = 3.2\ \text{mL}$.

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