What are the Measurement Systems Used in Pharmacy Calculations?

When you visit a pharmacy for medication, the technician will give you a prescription on how to take the drug. But, do you ask yourself how they come up with the measurements for each drug? This is a question that runs through most people minds wondering how the teaspoon of syrup or the single tablet is measured for treatment.

Like other products in the market, drugs also get measured to ensure what gets to the patient is as recommended by the relevant regulating bodies. 

On this note, which are the different measuring systems as far as medications are concerned? This article describes the various tech math applications and measurement systems used by pharmaceutical professionals. 

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The Metric System

This type of measurement system is one of the most widely used not only in the pharmaceutical industry but also in other areas of research and productions. In the United States, this system is the legal standard of measurement for pharmacies and other medical fields.

But, other methods also operate but in specified cases. The metric system has its basis on the decimal system. That means it all units are illustrated as multiples of 10. 

This system of measurement gives more distinct results that the others as far as correlations among units are concerned. Also, the metric system simplifies calculations and ensures accuracy and precision.

The metric system features various units that come in handy in the measuring processes. One of these is the meter to measure length or distance. The other is the liter to measure the volume of liquid and finally the gram for measuring dry weight such as powder.

These measuring units are used in pharmacies while measuring and dispensing drugs. The most common systems of measurement used in the pharmaceutical practice are for volume and weight. Dry powdered drugs or pills will always have a label for the exact weight they bear.

Some of the prefixes common to this are ‘mg' and ‘g' and feature in the packaging of the drug. The other is the liter which in most cases will feature as ‘ml' for most liquid form drugs.

The Apothecary System of Measurement

This is one of the ancient forms of measurement systems used in the medicine and science fields. This counts by the pound which in this case equals to 12 ounces. However, this system has one thing in common with the avoirdupois system which is the grain. This unit of measure is used to measure dry weight such as powder or pills.  

This system of measurement is not as accurate as the metric system. For this reason, it is highly discouraged to use in the pharmaceutical industry due to safety concerns.

For example, 1 grain equals to 64.79 milligrams. But in most presentations, this figure will appear as 64.8 or even 65. This discrepancy from the actual figure makes it quite inaccurate to use for drugs.

This system of measurement has been used in older versions of some drugs such as aspirin. The system uses weight and volume as the two different divisions of measurements. Other units of measure in this system are ounces, gallons, pints, and quarts.

There is a chance that most pharmacists still use this system of measurement since it was one of the most known in the early days.

The Household and Avoirdupois Systems of Measurement

These systems are standard in the United States in the sale of products such as food items. It has been replaced by the metric system, however, in some counties. The household system is most family among patients in most parts of the world.

This system consists of teaspoons, tablespoons, gallon, quarts, and pints.  

These units of measure are mainly used in the measuring of liquid products. Up to this day, most people will find measuring in teaspoons and tablespoons easier that using milliliters or pints. This explains why liquid drugs come with calibrated cups to help patients equate a tablespoon to the milliliters they should take.

The household system and the Avoirdupois are also useful in measuring weight. In both systems, ounces and pounds apply.

In contrary with the apothecary system, this two equates a pound to 16 ounces. When using this system for measurements, it is recommended to educate patients on how to convert between the metric and the household system.

In many instances, the household system will prevail, but in essence, the drugs come measured in either of the other two modes of measurement.

For this reason, the industry insists on telling the difference in milliliters and using a teaspoon for liquid drugs. The Avoirdupois system comes in handy in the measurement of bulk quantities when buying and selling of drugs.

Pharmacy Measurements Video 

US customary units and the metric system for pharmacy math:

Converting Gallons to Quarts, Pints, and Cups for Pharmacy Math:

Converting pounds to ounces for pharmacy math:

All the three systems of measurements have the primary aim of ensuring the patient gets the right prescription.

But, there could be certain discrepancies in some systems especially the Apothecary.

The most accurate system has proved to be the metric system although it is backed up by the other two. Whatever the case, these three play a significant role in the processing, prescription and dispensing of drugs.

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