What is a drug interaction?
Modification of a drugs effect by prior or concomitant administration of another drug
What are different things involved in drug interactions?
What is the object drug?
Drug which is effected by these interactions
What is the precipitant?
Agent which precipitants such a reaction
What are examples of drug interactions which are not always decremental?
What is epidermiology?
Branch of medicine that deals with incidence, distribution and possible control of disease
What is the incidence of significant interactions?
Relatively low at 1%
What are some examples of drug involved in serious reactions?
What are drugs involved in serious interactions often?
Potent with a narrow therapeutic index, meaning a small change in blood levels induce toxicity
What do lots of foods interact with?
What happens to the probability of a drug-drug interaction with more medicaments?
Who are some people more likely to suffer from a drug-drug interaction?
Patients undergoing complicated surgery procedures
Patients on many medications
What kinds of conditions make people susceptable to drug interactions?
What are examples of chronic conditions that make people more susceptable to drug interactions?
Who usually experience severe interactions?
Patients with chronic conditions
What is pharmacodynamics?
Study of how a drug affects an organism
What is pharmacokinetics?
Study of how the organism affects the drug
What can drug interactions be?
Additive or synergistic
What can interactions be due to?
Changes in drug transport
Fluid and elctrolyte disturbances
Indirect pharmacodynamics interactions
What are the 4 stages of pharmacodynamics?
What can a drug do to the pharmacokinetics of another drug?
Why is it possible to predict potential interactions?
Due to marked inter-individual variations in pharmacodynamics process
What is it not possible to predict?
Patients who will have a clinically significant interaction
What do absorption interactions mechanisms include?
Formation of insoluble complexes
Altered bacterial flora
Altered GIT motility
What do most absorption interactions lead to?
Change in absorption rate and not the extend of absorption
When is delayed absorption likely to have a great impact?
When the drug has a short half life or when we want high plasma levels quickly
How can absorption interactions be avoided?
2-4 hours are left between administration of drugs
What do some drugs do in the GI tract?
Bind to each other
What are examples of drugs that bind to each other in the GI tract?
Tetracycline and erythromycin complex with iron, calcium and magnesium
Cholestryamine resin used to bind cholesterol in the GI tract also binds to other drugs like warfarin
What is absorption affected by (relates to acids/bases)?
Degree of ionisation which is dependant on pH