What is Posology?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 09 December 2018
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Posology is a vital part of medical and pharmaceutical practice and study, not just for humans, but also for animals. It is the science of determining and understanding drug dosage, as based on research into a huge number of factors. To a limited or extensive degree, posology may be studied by anyone who wants to become a doctor, nurse, pharmacist, veterinarian, or pharmacologist.

Medications are great, and they have been invaluable to the sum of human medicine. They may cure some diseases completely, and they may greatly reduce symptoms of others. The issue of exactly what amount to give is one that must be carefully considered. Digitalis, for instance, can improve heart function, and it can kill people easily. Deciding how to give the right dose is thus extremely important, and those administering this drug need to know how to prescribe it appropriately.

The digitalis example is fairly straightforward, but the science of dosage is not. Drugs may react differently with different people, populations, ages, genders and if people take other medications at the same time. When pharmacologists attempt to create posology guidelines for others, they may enter their research with a number of inquiries.

Questions someone working in this area of posology might ask to determine drug dosage for whole populations include:

  • What is the level of toxicity?
  • What is the appropriate dose for children?
  • Do other medications have an effect on this drug, and does dosage have to be lowered or raised to counter this effect?
  • Does a drug work differently in elderly populations or child populations than it does in adult populations?
  • How are the effects of weight and dosage related?

These queries and many more are how drug companies arrive at safe dosing recommendations for those who will prescribe or administer the drug. It should be noted that both the study of these guidelines and the development of them are part of posology. Once guidelines are established, medical practitioners must know how to read and interpret them, determining within guidelines, the appropriate dosage. For instance there may be high and low dosages for many different drugs and a doctor can determine based on individual patient and patient response, what dose appears to be the correct one.

Given the huge number of medications, doctors don’t always know dosage guidelines on every single drug. They do have access to handy references, in either book form or online, that can tell them right away what the dosage parameters are for each individual. These may be called Summary of Product Characteristics (SPCs) in some regions. People reading extended product leaflets from pharmacy-issued medications may notice statistical information on correct dosing too, but it’s often hard to read for medical laypeople.

Posology is a valuable tool. It helps to prevent what could be devastating drug accidents by finding out in advance how much medication can and should be administered. The study of it also informs medical professionals exactly how to dose for each patient. Though the name is not well known outside of the medical field, those in medicine must respect it as a means of ensuring safety of patients and better quality of care.


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Post 3

What subjects are studied in posology? What is the sequence to study posology??

Post 2

Theophrastus Phillipus Auroleus Bombastus von Hohenheim (1493–1541) (Also called Paracelsus, from his belief that his studies were above or beyond the work of Celsus – a Roman physician from the first century) is also considered "the father" of posology and toxicology. It was his studies that first determined the toxicity of plants and other substances when used for medical purposes. He is credited with the classic toxicology maxim, "All things are poison and nothing is without poison; only the dose makes a thing not a poison."

Post 1

Who first studied and is considered the "Father of Posology"?

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