Drug Interactions Flashcards
What is a drug interaction?
Modification of drugs effect by prior or concomitant administration of another drug herb foodstuff drink.
What are the 5 types of drug interactions?
Drug Herbal Food Drink Pharmacogenetic
What is the object drug?
The drug whose activity is affected by the interaction.
What is the precipitant drug?
Agent which precipitates such an interaction.
What factors modify drug action?
Food
Smoking
Alcohol
Herbs
What drug interactions are not detrimental?
Treatment of hypertension
Treatment of Parkinsonism
What are the patient specific risk factors?
Advanced age
Genetic polymorphisms
Concomitant diseases
What are the drug specific risk factors?
Polypharmacy
Narrow therapeutic range
Dose
What are the other risk factors?
Multiple prescribing physicians
Self prescription
Prolonged length of stay
Drugs involved with serious interactions have narrow/broad therapeutic index.
Narrow
What are the drugs involved with serious interactions that are in the antimicrobial booklet?
Cyclosporin Gentamicin Fluconazole Clarithromycin Erythromycin Linezolid
What foods interact with warfarin?
Asparagus Broccoli Lettuce Onions Avocado Fish oils Liver
What herbals interact with warfarin?
Ginseng
Green tea
Who are susceptible patients?
Elderly
Young
Critically Ill
Patients undergoing complicated surgical procedures.
What chronic conditions make patients susceptible?
Liver disease Renal impairment Diabetes mellitus Epilepsy Asthma
What are the 2 mechanisms of drug interaction?
Pharmaceutical
Pharmacokinetic
What are the 4 stages of pharmacokinetic?
Absorption
Distribution
Metabolism
Elimination
What are the 4 types of pharmacodynamic reactions?
Antagonistic
Additive/Synergistic
Interactions due to drug transport
Interactions due to fluid/electrolyte distribution
What can you predict?
If there is a potential drug interaction, but not the clinical severity
What are the 4 mechanisms of absorption interactions?
Insoluble complexes
Altered pH
Altered bacterial flora
Altered GI motility
How are drug interactions stopped in absorption?
Time before and after taking pill before eating for example.
What does tetracycline/erythromycin bind to in the GI tract?
Iron
Calcium
Magnesium
Where are GI bacterial flora found?
Large bowel
What can GI bacterial flora lead to failure of?
Oral contraceptive
Digoxin toxicity
When does protein binding displacement occur?
When there is a reduction in the extent of plasma protein binding
What are the 2 most important proteins?
Albumin
Alpha 1-glycoprotein
Are drugs with protein binding greater than 95% common?
Yes
What does erythromycin/clarithromycin inhibit?
Cytochrome system
What does an inhibited cytochrome system cause?
Metabolism in liver failure.
What does tobacco induce?
Cytochrome P450 system
Where are most drugs excreted?
Urine
Bile
What occurs in elimination?
Changes in GFR or tubular secretion
What are the 4 ways pharmacodynamic interactions can occur?
Direct
Indirect
Antagonistic
Synergistic
What is an example of direct antagonism?
Beta-blockers
What happens in synergistic interactions?
When two drugs with the same pharmacological effect act on the same receptor at the same time.
What is CNS depression interactions?
Indirect agonism
