Drug therapy Flashcards
What are drug interactions?
Changes to the effect of a drug that happen prior to or along side the administration of another drug, herb, food, or drink. They are normally harmful but sometimes are useful such as in hypertension.
What are some of the terms used in drug interactions?
The drug which is altered is called the ‘object drug’ and the agent which causes the change is called the ‘precipitant’.
What are drug to drug interactions?
Drug to drug interactions occurs when two drugs are used together.
What do drug to drug interactions depend on?
- Features of the patient i.e. there age.
- Features of the drug i.e narrow therapeutic range
- Multiple doctors
- Self -prescription
- Prolonged length of hospital stay
- Number of drugs that the patient is on. The changes of a drug to drug interaction increases exponentially the more drugs you take.
What are the three categories of drug to drug interactions?
- Pharmaceutical
- Pharmacokinetic
- Pharmacodynamic
What is a pharmakinetic drug to drug interaction?
Pharmacokinetic interactions can causes change in;
- Absorption (gut motility, gastric pH, chelation)
- Distribution (Plasma proteins binding competition)
- Metabolism (cytochrome P450 induction/inhibition)
- Elimination (renal or bile)
What is a pharmodynamic interaction?
There are five types of pharmodynamic drug to drug interaction.
- Direct antagonism (Beta blockers block the action of beta agonists such as salbutamol)
- Antagonistic interactions
- Agonistic
- Synergist
- Indirect
What is an ADR?
An adverse drug reaction.
an appreciably harmful or unpleasant reaction, resulting from an intervention related to the use of a medicinal product, which predicts hazard from future administration and warrants prevention or specific treatment, or alteration of the dosage regimen, or withdrawal of the product.
What is a medication error?
An error in the prescribing, dispensing or administration of a drug.
What is an adverse drug event?
Any harmful even that occurs after taking medication regardless if it way due to the drug.
What are the different types of ADR?
Acute - Arises within the first 60 mins i.e. Anaphylaxis
Sub-acute - Arises within the first 24 hours i.e. rash or serum sickness.
Latent - More than 2 days i.e. eczema.
What are the different severities of a ADR?
Mild (bothersome but not requiring therapy)
Moderate (Requiring therapy)
Severe (causing disability or life threatening)
What is the relationship between medication errors, ADRs and ADEs ?
All Adverse drug reactions are Adverse drug events.
Some adverse drug events and adverse drug reactions are medication errors.
What are the different classifications of ADRs?
Type A - Augmented. These are the most common. They are normal but augments responses to a drug, they are predictable and dose dependant. They are easily reversable. They are often the result of a unique feature of the patients i.e. renal failure.
Type B - Bizarre. Unpredictable, serious, might last a long time, not readily reversable. Can be caused by a drug allergy or hypersensitivity.
Type C - Chronic. Related to the duration of treatment and dose.
Type D - Delayed. Lasts a long time. i.e. lymphomas in patients who have previously had chemo.
Type E - End of treatment. occurs when a drug is stopped abruptly.
Type F - Failure of treatment. Common and dose related caused by drug interactions.
How are ADRs monitored?
Yellow card system
Green card system (for select samples of a population)
