Drug Interactions

Question 1

What are behavioural drug-drug interactions?

Answer 1

drug alters patient’s behaviour to modify compliance with another drug

e.g. depressed person taken anti-depressant may be more compliant with meds as symptoms improve

Question 2

What are pharmaceutical drug-drug interactions?

Answer 2

Formulation of one drug is altered by another before it is administer

e.g. precipitation of sodium thiopentone and vecuronium w/in intravenous giving set

Question 3

What are pharmacokinetic drug-drug interactions that alter bioavailability?

Answer 3

When amount of object drug reaching systemic circ is limited by a perpetrator drug

Oral drugs = absorption/first-pass metabolism is altered (those w/ low oral bioavailability are affected most)

Question 4

What are pharmacokinetic drug-drug interactions that alter distribution?

Answer 4

Concentration of drug at site of action changes w/out necessarily altering its circulating concentration

Issue for drugs w/ intracellular/CNS targets

e.g. verapamil inhibit efflux transporters inc digoxin and cyclosporine

Question 5

What are pharmacokinetic drug-drug interactions that alter clearance ?

Answer 5

Metabolism or excretion of the object drug is affected by a perpetrator drug

Question 6

What pharmacokinetic drug drug interactions alter the clearance by influencing metabolism?

Answer 6

E.g. CYP3A4 inhibitors = erythromycin, verapamil. grapefruit juice

E.g. CYP3A4 inducers = carbamazepine, rifampicin

Question 7

What does inhibition of CYP P450 enzymes do?

Answer 7

inc concentration of some drugs –> dec metabolism

Question 8

What does induction of CYP P450 enzymes do?

Answer 8

dec concentration of some drug by inc metabolism