Key Medication Management terms

Key Medication Management Terms

This Module will cover key technical terms that play an important role in ensuring that medicines are dispensed and administered safely and correctly.

In this lesson, we will be covering key technical terms that play an essential role in ensuring that medicines are dispensed and administered both safely and correctly. You will gain an understanding of the following terms:

  • Therapeutic Index
  • Half-Life
  • Steady State
  • Potency

Therapeutic Index:

In general, the effects of a drug on the body are directly proportional to the amount (concentration) of the drug in the blood; The higher the concentration, the greater the pharmacological effect (either positive or negative).

This, however, is not the care with all drugs. In some drugs, there is what is classed as a “ceiling”  to the positive pharmacological effect.

Some drugs can cause an allergic reaction in the user, even at extremely small doses.

The therapeutic index is the difference between the therapeutic dose and the toxic dose of a drug.

The therapeutic margin is the difference between the therapeutic concentration in the blood and the toxic concentration in the blood of the drug.

  1. Therapeutic Dose – A dosage at this level of concentration of the drug in the blood and has the desired beneficial effect.
  2. Toxic Dose – At this dosage level  there are signs of toxicity which occur in the blood. It is generally higher than the therapeutic index.

The Dosage Margin

If the margin of the therapeutic dose and the toxic dose is wide / large, then the drug is classed as relatively safe.

There are drugs however where the margin between the therapeutic dose and the toxic dose is very narrow. These drugs with just a small increase in the dose will cause a toxic effect or toxic dose.

There are many problem drugs with a narrow therapeutic index examples of drugs. This includes Warfarin and Digoxin.

Drugs that have a narrow therapeutic index require the client to be regularly monitored with a blood test as part of their monitoring process. Some further examples of drugs with narrow therapeutic index include:

  • Carbamazepine
  • Digoxin
  • Lithium
  • Phenytoin
  • Theophylline
  • Warfarin

“Problem Drugs” are commonly referred to in Adverse Drug Reactions (ADR) which we will cover later on in this course.

For further learning on the Therapeutic Index please read:

Half Life:

The half-life of a medication is the measure of how long a drug will stay in the body after it has been administered.

Therefore, the dosage’s half-life is the length of time needed for the concentration of the drug in the blood plasma to be halved.

So, for example, if a medications half-life is 1 hour the following would apply:

Drug Level RemainingTime
100.00%  0.00 hrs
50.00%  1.00 hr
25.00%  2.00 hrs
12.50%  3.00 hrs
6.25%  4.00 hrs
3.13%  5.00 hrs

This is an estimate on the time it will take for a drug to be removed from the body.

The actual half-life of the same drug may vary significantly from person to person because it depends on several different patient-specific and drug-specific variables.

Half-life is important – if a drug has a long half-life it would mean it needs to be taken less frequently for example once a day or less often.
However, a medicine with a short half-life will need to be taken more frequently.

Steady State:

“Steadystate concentration occurs when the amount of a drug being absorbed is the same amount that’s being cleared from the body when the drug is given continuously or repeatedly.”

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