Drug Interactions Flashcards
What is type A reaction and when are they likely?
AUGMENTED- Pharmacological toxic effect
Likely with higher doses
What is a type B reaction and when are they likely?
BIZARRE - idiosyncrasy and drug allergy - pharmacologically unexpected and unpredictable
No dose relationship and not producible
What is the therapeutic index?
Range of drug dose that can tx disease effectively w/o toxic effect
Factors that can cause adverse drug reaction?
Circumstance - accidental/ deliberate over dose
Site action
Time course
Describe difference between acute, sub-acute and chronic toxicity
Acute toxicity - single intake w/ rapid onset
Sub-acute toxicity - repeated exposure (hours/days)
Chronic toxicity - repeated exposure (month/yrs) - e.g carcinogen
Explain type A reaction inc main/ minor concerns
Exaggerated therapeutic response - secondary unwanted action
Main concern: resp depression, cardiac toxicity
Minor: diarrhoea, dry mouth, drowsiness
RF for type A reaction?
Elderly, pregnancy and renally impaired
How is absorption/ distribution of tetracycline changed in type A reaction?
Sequestration of tetracycline in bones - depression growth and irreversible tooth straining
Don’t prescribe pregnancy and children
What are factors dispose people to drug allergy?
Drug related: nature of drug, degree exposure inc. route admin, cross sensitisation
Host factor: age (20-49 highest risk), genetic, previous exposure
What is Stephen Johnson syndrome and in what reaction would you see it?
Type B
Common w/ anti-gout, anti-biotic, anticonvulsant and antipsychotics
Flu like symptoms followed by painful blister like rash
Relationship between adrenaline and lidocaine?
Adrenaline increase therapeutic effect lidocaine - slow absorbance into systemic circulation
Problem erythromycin?
Inhibit CY3A4 - decrease clearance - increase amount drug –> increase effect warfarin, cyclosporin
Problem St John’s wort?
Enhance metabolism of drug reducing plasma levels - induce CY3A4
Risk OCP and immunosuppression
