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Questions and Answers
What is the equivalent of 1 teaspoonful in millilitres?
What is the equivalent of 1 teaspoonful in millilitres?
Which of the following is NOT a common instrument for measuring volume in pharmacy?
Which of the following is NOT a common instrument for measuring volume in pharmacy?
Which measurement device should be chosen to minimize errors of measurement?
Which measurement device should be chosen to minimize errors of measurement?
What volume does a tumblerful equal in millilitres?
What volume does a tumblerful equal in millilitres?
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Which of the following instruments is primarily used for analytic procedures?
Which of the following instruments is primarily used for analytic procedures?
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What is the equivalent volume of 1 wineglassful in millilitres?
What is the equivalent volume of 1 wineglassful in millilitres?
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Which of the following measurements is equivalent to 1 desertspoonful?
Which of the following measurements is equivalent to 1 desertspoonful?
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In pharmacy practice, what is the most common instrument for measuring volume?
In pharmacy practice, what is the most common instrument for measuring volume?
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What error is minimized by using a calibrated pipet or syringe?
What error is minimized by using a calibrated pipet or syringe?
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Which of the following measurements does not represent a precise volume?
Which of the following measurements does not represent a precise volume?
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What is the main advantage of using the metric system for pharmacy calculations?
What is the main advantage of using the metric system for pharmacy calculations?
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Which of the following is NOT a measurement used in the apothecary system?
Which of the following is NOT a measurement used in the apothecary system?
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In the context of pharmaceutical measurements, what could a small percentage of error potentially lead to?
In the context of pharmaceutical measurements, what could a small percentage of error potentially lead to?
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What is the purpose of the aliquot method in pharmaceutical calculations?
What is the purpose of the aliquot method in pharmaceutical calculations?
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When converting from a larger metric unit to a smaller unit, what must be done with the decimal?
When converting from a larger metric unit to a smaller unit, what must be done with the decimal?
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Which statement accurately reflects the Avoirdupois system?
Which statement accurately reflects the Avoirdupois system?
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What is the primary role of a pharmacist in the context of pharmaceutical care?
What is the primary role of a pharmacist in the context of pharmaceutical care?
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Sensitivity requirements in pharmaceutical measurement refer to what?
Sensitivity requirements in pharmaceutical measurement refer to what?
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Which system of measurement is most commonly used in pharmacy due to its ease of use?
Which system of measurement is most commonly used in pharmacy due to its ease of use?
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What is a key characteristic of the apothecary system?
What is a key characteristic of the apothecary system?
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Study Notes
Pharmaceutical Measurement
- Pharmaceutical care involves accurate weighing, measuring volume, and combining components.
- Incorrect calculations impact dosage and can harm patients.
- Accurate component calculation and measurement are crucial steps in compounding.
- Three measurement systems are used: Metric, Apothecary, and Avoirdupois.
Metric System
- A decimal system based on a factor of 10.
- Common in pharmacy calculations for quick and easy conversion.
- Conversions from smaller to larger units involve moving the decimal to the left.
- Conversions from larger to smaller units involve moving the decimal to the right.
- Basic units: gram (g) for mass, meter (m) for length, and liter (L) for volume.
- 1 cubic centimeter (cc) of water is approximately equal to 1 milliliter (mL) and weighs 1 gram (g).
Apothecary System
- Uses weight and volume as divisions of measurement.
- Includes measurements of ounces, gallons, pints, and quarts.
- Historically used by apothecaries, pharmacists, and alchemists.
- Still used today by pharmacists as their primary measurement system.
Avoirdupois System
- A system of weight measurement only.
- The basic unit is the grain (gr), same as in the apothecary system.
Conversion Equivalents
- Length: 1 meter (m) = 39.37 inches (in), 1 inch (in) = 2.54 centimeters (cm).
- Volume: 1 milliliter (mL) = 16.23 minims (m), 1 fluid dram (fl dr) = 60 minims (m).
- Volume: Additional conversions for fluid ounces, pints, quarts, and gallons are provided.
- Mass: 1 gram (g) = 15.432 grains (gr), 1 kilogram (kg) = 2.20 pounds (lb), 1 ounce (oz) = 28.35 grams (g), 1 pound (lb) = 454 grams (g).
- Approximate equivalents: 1 fluid dram = 1 teaspoonful = 5 mL, 4 fluid ounces = 120 mL, 8 fluid ounces = 1 cup = 240 mL, 1 grain = 65 mg, 1 kg = 2.2 pounds (lb).
- Household equivalents Common household equivalents are given.
Measurement of Volume
- Common instruments: micropipets, burettes, graduated cylinders, and flasks.
- Instrument choice depends on needed precision.
- Cylindrical and conical graduates are common in pharmacy.
- Pipettes and calibrated syringes are used for smaller volumes.
- Erlenmeyer flasks, beakers, and prescription bottles are NOT volumetric glassware.
Guidelines for Selecting Liquid Measurement Devices
- Select the smallest device that accommodates the desired volume to reduce measurement error.
- Use graduated pipettes, syringes, or calibrated droppers for volumes less than 1 mL.
- Oily and viscous liquids might require specialized handling.
- Avoid using non-volumetric containers for accurate measurements unless calibrated.
- Use calibrated droppers, oral syringes, or similar devices for very small or exact dosages.
Measurement of Weight
- Class A prescription balances are required for compounding.
- These balances have a sensitivity requirement (SR) of 6 milligrams or less.
- Balances can handle a load of 10 grams in each pan.
- Weighing less than 120 milligrams can lead to errors greater than 5%.
- Most commercially available Class A balances have a maximum capacity of 120 grams.
- Sensitivity requirement is defined as the load causing a 1-unit change on the index plate.
Aliquot Method
- Used to obtain precision beyond instrument capacity.
- An aliquot is a fraction of a larger amount.
- Steps for weighing by the aliquot method are described.
- The method involves weighing a multiple of the desired quantity and diluting it with an inert substance.
- The resulting aliquot contains the desired quantity.
Minimum Measurable Quantity
- The minimum measurable quantity is determined using the sensitivity requirement and acceptable error to determine the smallest quantity that can be reliably measured.
Least Weighable Quantity Method
- An alternative approach to the aliquot method for obtaining small quantities of a drug substance.
- Weigh a quantity of the drug substance above the least weighable amount, dilute it with an inert substance, and weigh the calculated portion.
- This will contain the desired quantity of drug.
Percentage of Error
- Percentage error is crucial in pharmacy to ensure that measurements are as accurate as possible.
- Percentage error is calculated by multiplying the error by 100 and dividing it by the desired quantity.
- Use this formula to ensure errors fall within permissible limits for a given set of tools.
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Description
This quiz covers essential concepts in pharmaceutical measurement, including the importance of accuracy in weighing and measuring components. It explores the three primary measurement systems: Metric, Apothecary, and Avoirdupois, and their relevance in pharmacy calculations. Test your knowledge on these critical topics to ensure patient safety.
