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Questions and Answers
1 gram is equivalent to 1000 milligrams.
True
To convert inches to centimeters, one should multiply by 2.54.
True
A child weighing 30 kg would need 45 mL of Paracetamol if the dosage is 15 mg/kg QDS.
False
The stock of Ranitidine syrup is 15 mg/mL.
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Dispensing calculations do not involve dimensional analysis.
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To find out how many tablets a patient takes daily of Metformin 1 g when stock availability is 500 mg/tablet, 4 tablets are needed.
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Weight-based dosing requires calculating the dose based on the child's weight in order to determine the correct volume of medication.
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The total daily dose of Ranitidine syrup for a patient taking 150 mg BD is 300 mg.
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1 week is equal to 150 hours.
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Corticosteroid dispensing is not covered in dispensing calculations.
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To provide 150 mg of dextrose, 3 mL of D5W is required.
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To prepare a 250 mL solution at 15% (v/v) from an 80% (v/v) stock solution, 30 mL of stock solution is needed.
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The total volume used in the B.M.X formula is 240 mL.
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The concentration of a 0.5% w/w sulphur ointment can be achieved by adding more yellow soft paraffin to 50g of 2% sulphur ointment.
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A hygoglycaemic patient requires the administration of 5g of dextrose in D5W.
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The formula for B.M.X includes 20 mL of Lidocaine.
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To calculate the volume of stock solution needed, one simply compares the dilution ratio directly without performing calculations.
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The calculation for the required amount of Maalox liquid to make 500 mL of BMX results in 229 mL.
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The dilution of solids requires a liquid component to effectively lower the concentration.
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The calculation for finding mL of D5W needed for 150 mg of dextrose is incorrect if the patient is in a hyperglycaemic state.
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To prepare a 25% salicylic acid ointment from 500g of a 10% ointment, 100g of salicylic acid must be added.
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In a 1-in-400 stock solution, 1 mL is diluted to make a 1-in-2,000 solution.
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An 8% w/v solution of Drug X requires 400 mg of the drug for 5 mL.
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The ratio of Chlorhexidine Gluconate to Cetrimide in a concentrated antiseptic solution is 20:1.
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Adding 5 g of solid to 45 g of base results in a % w/w strength of 10%.
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To achieve a 15% salicylic acid ointment from 680g of a 10% ointment, 48g of salicylic acid must be added.
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The total weight of an ointment when preparing a concentrated solution must account for both active and inactive ingredients.
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If a 25 mL sachet contains 0.015% w/v Chlorhexidine, it contains 0.00375 g of Cetrimide.
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A 1-in-400 dilution of a stock solution means that 1 part of the stock solution is mixed with 400 parts of the diluent.
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To prepare a 25% w/w ointment, the amount of API plus excipients must always equal the total weight of the ointment.
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For a 30 kg child, the recommended dose of Paracetamol is 600 mg per administration.
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A bottle of lactulose lasting for 4 days requires a dosage of 3 x 5 mL spoonfuls three times a day.
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The total amount of codeine required for a 15 kg child is 300 mcg.
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To fill a prescription of Prednisolone 40 mg x 5/7, a total of 8 Prednisolone 5 mg tablets must be supplied.
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The final volume of the Paracetamol suspension administered in each dose is 15 mL.
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The amount of Prednisolone tablets decreases by 1 tablet every 5 days until reaching 0.
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A single dose of codeine for a 15 kg child equals 0.6 mL if available as a 5 mg/mL solution.
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To maintain the daily dosage of Prednisolone, the total tablets for a 5-day regimen would total 15 tablets.
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A volume of 400 mL of lactulose will last approximately 8.3 days if taken according to its dosage regimen.
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If lactulose is dosed 3 times daily at 5 mL per dose, a total of 15 mL per day is consumed.
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Study Notes
Medicine Dispensing
- Interpretation of dosage instructions is crucial for safe medication dispensing
- Calculations are not done by the patient but by the dispenser
- Dosage forms adapt to different age demographics, using forms suitable for children
- When dispensing medicine, always verify correct unit, dose, and frequency
Dispensing Solid Dosage Forms
- Example: Metformin 1 g tab BD (Twice daily)
- Stock: 500 mg tablets
- Calculation: To determine the number of tablets for daily dosage, divide total daily dose by tablet strength:
(1000 mg / 500 mg) * 2 = 4 tablets
Dispensing Liquid Dosage Forms
- Example: Ranitidine syrup 150 mg BD
- Stock: Ranitidine syrup 15 mg/mL
- Calculation: To determine the milliliter volume per dose, divide desired mg dose by concentration: 150mg / 15mg/mL = 10mL. To get the daily total, multiply by frequency: 10 mL * 2 doses = 20 mL
Weight-Based-Dosing
- Example: Paracetamol suspension 15 mg/kg QDS x 5/7 (Four times a day for 5 days)
- Susp available as 200 mg/mL
- Child weight: 30 kg
- Calculation:
- Calculate total daily dose (mg/kg * kg * frequency) = 15 mg/kg * 30 kg * 4 doses = 1800 mg.
- Calculate total dosage for prescribed days (total daily dose * days) = 1800 mg * 5 days = 9000 mg
- Calculate the number of mL needed (total dosage in mg / concentration of suspension in mg/mL) = 9000 mg/ 200 mg/mL = 45 mL
Corticosteroid Dispensing
- Example: Prednisolone 30 mg x 6/7 (For 6 days) Reduce by 5 mg every 6 days until 0.
- Calculation:
- Determine the number of tablets needed for each day's dosage, then add the total: Day 1-6: 6 tablets. Day 7-12: 5 tablets. Day 13-18: 4 tablets. Day 19-24: 3 tablets. Day 25-30: 2 tablets. Day 31-36: 1 tablet
- Sum individual tablet count for all days
- Alternatively: Use the sum of consecutive integers formula n*(n+1)/2, where n is the maximum tablets per day. Multiply by the number of days for the total tablets.
Dimensional Analysis
- Method used to convert units of measurement
- Example:
- 5 inches to centimeters (5 in * 2.54 cm/in = 12.7 cm)
- 1 week to hours (1 wk * 7 d/wk * 24 hr/d = 168 h)
Compounding
- It involves combining different ingredients to create medications
- Currently, prefabricated pharmaceutical forms are more commonly used for compounding
Calculations with Ratios and Proportions
- Example:
- How many milliliters of D5W (5% dextrose) provides 150 mg of dextrose?
- Concentration stays constant
- Calculation: (150 mg * 1 g/1000 mg * 100 mL/ 5 g) = 3 mL
Dilution of Stock Solution (Liquids)
- Example:
- Prepare 250mL of 15% (v/v) solution from a stock of 80% (v/v) solution
- Active Pharmaceutical Ingredient quantity stays constant
- Calculation: (15 * 250) / 80 = 46.875 mL
Following a Formula
- Example:
- B.M.X. formula: Benylin 110 mL, Maalox 110 mL, Lidocaine 2% 20 mL
- Prepare 500 mL of BMX
- Concentration quantity stays constant
- Calculation: (110 mL / 240 mL) * 500 mL = 229 mL (rounded to nearest whole number)
Dilution of Solids
- Example:
- 50 g of 2% sulphur ointment to 0.5% w/w sulphur ointment
- Active Pharmaceutical Ingredient quantity stays constant
- Calculation:
- Calculate the initial amount of sulphur in the ointment: (2/100) * 50 g = 1 g
- Calculate the amount of yellow soft paraffin needed to dilute the ointment to the desired concentration:
- (0.5 g / 100 g) = (1 g) / (1 g + 49 g + X) = 100 / ( 50 + X) = 0.5.
- Solve for X: X = 200 g - 50 g = 150 g
Increasing Concentration
- Example:
- Add salicylic acid to 500g of 10% salicylic acid ointment to create a 25% solution
- Active Pharmaceutical Ingredient quantity stays constant
- Calculation:
- (25 / 100) = (50 + X) / (50 + X + 450). Expand and solve for X.
- 25(50 + X + 450) = 100 (50 + X)
- 1250 + 25X + 11250 = 5000 + 100X
- 7500 = 75X
- X = 100 g
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Description
Test your knowledge on the essential principles of medicine dispensing, including dosage calculations for solid and liquid forms. This quiz covers various scenarios, such as age-appropriate dosing and weight-based dosing methods. Ensure you understand the critical safety measures involved in medication dispensing.
