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The Historical past Behind Aspirin 81 – Scientific Correlations

The Historical past Behind Aspirin 81 – Scientific Correlations

2023-11-26 13:53:59

By Joshua Novack

Peer Reviewed

Sufferers usually come into clinics on a grocery checklist of medicines. Widespread prescriptions embody lisinopril 20 mg, amlodipine 2.5 mg, metformin 500 mg, and aspirin 81 mg. One dosage stands out from the others. Whereas most drugs are available dosages of spherical numbers or widespread decimals, low-dose aspirin has a regular dose of 81 mg.

Why is aspirin out there at a dose of 81 milligrams? The reply is historic in nature and is rooted in a medieval and now defunct system of measurement known as the apothecary system of weights and measures. The complete rationalization of aspirin 81 requires some background data on the apothecary system and is greatest defined compared to the extra acquainted metric system.

The apothecary system of weights and measures was developed and formalized in England and France in the course of the early Center Ages. This method got here for use for remedy dosages earlier than the event of the now-standard metric system within the late 1700s. Within the metric system, mass is predicated on the kilogram, with different items outlined relative to the kilogram. For instance, the gram is one one-thousandth of a kilogram, and one milligram is one one-millionth of a kilogram. Within the apothecary system, the bottom weight was derived from the load of a grain of barleycorn. This unit was creatively termed the grain, abbreviated gr.1 The grain is equivalent to 64.8 mg.2

The grain was used to outline the bigger items within the apothecary system. England and France each used scruples, drams (typically written as drachme), ounces, and kilos as bigger items constructed from the grain. Nevertheless, the international locations outlined the items in a different way. In France, 24 grains fashioned 1 scruple, whereas in England, 20 grains fashioned 1 scruple.1 Above that, the methods had been aligned, with 3 scruples making one dram, 8 drams making one ounce, and 12 ounces making one pound.1,3 That’s appropriate: versus the trendy pound (also called the avoirdupois pound), 12 ounces made 1 pound, versus 16 ounces.1 The variations between the variety of grains in a scruple between the 2 international locations led to at least one English ounce weighing 480 gr, whereas one French ounce weighing 576 gr. One English pound weighed 5760 gr, and one French pound weighed 6912 gr.

Of observe, the barleycorn grain has a historical past of getting used to derive different items. The medieval English inch was outlined as three medium-sized barleycorn grains positioned end-to-end, which is approximately the same length of the inch used in America to this day.4

In 1790, French scientists, on the request of the French authorities, started to plan a brand new measurement system, resulting in the creation of the metric system. By 1799, the kilogram was defined as the mass of one cubic decimeter of water at 4 degrees Celsius.5 After being established in France, the metric system was instituted in England by way of laws in 1824, 1878, and 1963.1

Regardless of the swap to the metric system within the 19th century, the apothecary system was nonetheless generally utilized in pharmaceutical preparations. Within the mid-1800s, shortly after the adoption of the metric system, physicians printed articles within the British Medical Journal calling for the British Pharmacopeia to permit for remedy formulations to be described and prescribed by way of each the apothecary system and the metric system. These calls had been initially ignored. By 1885, the apothecary and metric methods had been allowed for volumetric measurements for medicinal options, and by 1898 volumetric measurements had been solely listed in metric. In 1951, the move was made to begin abolishing the apothecary system in totality, completed by 1963.6

In the USA, the American Pharmacopeia started to slowly embody the metric system alongside the apothecary system in 1883, with the metric system totally built-in alongside the apothecary system by 1894. In 1900, nonetheless, solely 6% of American prescriptions had been written within the metric system. The twin system endured into the Forties as a result of prescribing practices of American medical doctors, who solely slowly took up prescribing in metric. In 1943, the American Medical Affiliation dominated that the publications of its Council on Pharmacy and Chemistry would solely use the metric system. In the 1980s, some physicians continued to prescribe in grains.7 In 1993, the USA Pharmacopeia formally terminated the usage of the apothecary system, 30 years after the British Pharmacopeia.2,8

Aspirin, codeine, and morphine had been a few of the medication generally ordered in grains versus milligrams.2,8 Aspirin dosing is rooted on this historical past. The usual grownup aspirin dose was 5 gr, or 325 mg in metric, the dose nonetheless used at present for analgesia. Low-dose aspirin was one quarter of the usual dose, 1.25 grains, which transformed to 81 mg. This dosing regimen has persisted to modern times.8

See Also

Though the apothecary system of weights and measures is now not in official use, its impression remains to be alive at any time when physicians prescribe aspirin 81 mg, serving as a connection to the prescribing practices of generations of physicians and pointing to the hidden and untaught historical past of pharmaceutical weights and measures.

By Joshua Novack, a third yr medical pupil at NYU Faculty of Drugs

Reviewed by Dr. Michael Tanner, affiliate editor, Scientific Correlations


  1. Zupko RE. Medieval apothecary weights and measures: the principal items of England and France. Pharm Hist. 1990;32(2):57-62.
  2. Lipman AT. The top of the grain: The lengthy awaited transfer to metric. J Pharmaceutical Care Ache Symptom Management. 2010;2(3):59-61. 
  3. Britannica TEoE. Apothecaries’ weight. In. Encyclopaedia Britannica: Encyclopaedia Britannica, Inc.; 1998.
  4. Britannica TEoE. Grain: unit of weight. In. Encyclopaedia Britannica: Encyclopaedia Britannica, Inc.; 1998.
  5. Nationwide Bodily Laboratory. What’s the historical past of weighing? FAQ–mass and density. Printed October 8, 2007. Up to date February 17, 2012. Accessed Dec 29, 2018.
  6. Cartwright AC. The British pharmacopoeia, 1864 to 2014: Medicines, worldwide requirements and the state. Burlington, VT: Ashgate Publishing Firm; 2015.
  7. Higby GJ, Sonnedecker G. Adoption of the metric system by the U.S. Pharmacopoeia. J Hist Med Allied Sci. 1985;40(2):207-213.
  8. Aronson SM. The traditional vocabulary of medical prescriptions. R I Med J (2013). 2014;97(9):67.


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