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Weights and Measures - Imperial and Metric System

Measuring Systems: Their Importance, Metric system, Imperial system, Apothecary system, Apothecary weight, Apothecary liquid volume etc.
Calculations, calculations, and conversions are fundamental to being an effective pharmaceutical professional. Formulations, ingredients, and components of medication dosages are calculated and converted in the pharmaceutical measurement system. Different measurement methods are used when assessing pharmacy calculations. A pharmacist should be able to perform crucial pharmacy functions using three different measurement systems, which must be familiarized with.

Measuring Systems: Their Importance

Pharmaceutical professionals need to know how to perform accurate pharmaceutical calculations, measurements, and conversions. To function effectively in their day-to-day work duties, pharmaceutical professionals need to be able to apply their knowledge of pharmacology practically. If any of the above factors are wrong, the dosage can be adversely affected, and can potentially harm a patient. Having a working understanding of pharmaceutical systems of measurement will be beneficial to pharmaceutical professionals.

Metric system

Measurements are made up of eight digits of decimal numbers with all multiples and divisions based on multiples of 10. Additionally, this system of measurement is also the most frequently used for pharmacy calculations due to its ability to quickly and easily convert between multiple systems of measurement. As long as the decimal is moved to the appropriate number of places left after converting from smaller to larger, any metric conversion would be considered complete. To convert the larger number to the smaller number, the decimal would be moved to the right the necessary number of places.

Although Pharmacy, in general, uses the centimeter, which is 0.01meter (or one-hundredth of a meter) instead of the meter as the basic SI unit of length.

Despite not being an SI unit, but taking into account the volume of liquids, the liter (L) is an acceptable unit for measuring volume in SI. It is essentially a volume of 1,000 cubic centimeters (cm3), which is the primary unit of volume used in the pharmacy and medicine fields. When the cubic centimeter is expressed with the abbreviation "cc", it does not follow the SI conventions. SI uses the kilogram as its official basic mass unit, but the gram (g) is used as its basic stem unit. At 4°C, 1 gram of water is 1 cm3 of mass. One mL of water (1 mL = 0.001 L) has a mass of 1 g since it has a volume of 1 cm3. We typically say "weight" when we mean "mass", and kilograms and grams accurately represent mass, not weight. The terms mass and weight will be used interchangeably in this text, despite weight being technically a measure of force, which is equivalent to mass times gravitational acceleration.

Part two: In addition to meters (m), liters (L), and grams (g), metric units are determined by applying prefixes to these units. Several power of tens is multiplied by the stem unit to produce the prefix.

Imperial system

The imperial system falls into two types as mentioned below:

Apothecary system

Among the three standard methods of calculating pharmacy quantities in weight and volume, the apothecary system is one of them. In addition to ounces, pints and quarts are also included here. For apothecaries, pharmacists, and alchemists, this is the system of weights and measures used to dispense and prescribe medications. Despite modern technology, pharmacists still primarily use the apothecary system as their main measurement method.

Apothecary weight

Pharmacies and medical institutions use apothecaries' scales for mass. It is strongly discouraged that this system of measurement is used. However, some older compounding formulas are written in this format, so understanding how to convert apothecaries' quantities into metric values is important.

Apothecaries employed the grains, the scruples, the drams (i.e., drachms), the ounces, and pounds as their mass units. There is no mass difference between the apothecaries' system and the avoirdupois system (or in the British Imperial system).

Apothecary liquid volume

United States commercial and household use of the apothecaries' system of liquid measurement is common. Formerly, just like the apothecary's weight system, it was used for compounding formulas and prescribing medicines. It is no longer an official method of medical and pharmacological practice, and its use is strongly discouraged. For this system, volumes are measured in minims, fluid drams, and fluid ounces, as well as pints, quarts, and gallons.

Avoirdupois system

As with the apothecary system, the avoirdupois system measures weight exclusively as weight-based on 16-ounces being equivalent to 1 pound. People are familiar with this form of measurement because it is the standard weight-measuring system. Auxiliary measurements, such as over-the-counter products and chemicals, can be measured correctly using the avoirdupois system when purchasing or selling.

A metric system known as avoirdupois is a method of weighing objects commonly used in commerce and households in the United States. Despite the U.S. government's strong advocacy for the conversion to the metric system (called metrication), it has been very challenging to get the general population and industry to adopt SI units. Weight is still measured by pounds, we still buy butter and meat by the pound and pasta and cereal by the ounce, and we still have the postage calculated by ounces and pounds for letters and packages.

Under the avoirdupois system, the grain is the basic unit of mass, followed by the ounce and the pound. As far as the avoirdupois grain is concerned, its mass is the same as that of the apothecaries' system grain, but ore and pound differ in each system.

Some countries in the Commonwealth, including the United Kingdom, use the British Imperial mass system. The avoirdupois system uses the same units for grains, ounces, and pounds. A kilogram is equivalent to 453.59237 grams in the metric system and 1 pound is equivalent to 453.59237 grams in the avoirdupois system.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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