Lecture 10 - Medicine Interactions

Question 1

Drug interaction definition?

Answer 1

change in one drug’s effect administered with another drug, food or other substance

Question 2

Pharmacokinetic interactions?

Answer 2

interacting drug alters concentration, alters absorption, metabolism and elimination, difficult to anticipate

Question 3

Pharmacodynamic interactions?

Answer 3

interacting drugs alter effect, receptor/non-receptor mediated, able to anticipate from individual drug effects

Question 4

Drug interactions altering absorption?

Answer 4

GI pH, drug binding in GI tract, changes in gut motility, malabsorption - e.g. calcium binding thyroxine

Question 5

Enzyme inhibitors?

Answer 5

rapid increases in substrate, time to maximal drug interaction determined by half-life and time to steady state

Question 6

Enzymes inducers?

Answer 6

slow change due to requirement for enzyme synthesis (weeks).

Question 7

Enzyme that metabolises most of medicines?

Answer 7

CYP3A4

Question 8

Drug interactions alternating renal elimination?

Answer 8

change in renal blood flow, competition of use for same transporter, competition for ionic cotransport, change in urine pH

Question 9

Drug interaction alternating renal elimination - e.g.?

Answer 9

cimetidine competes with metformin for transport into renal cells and excretion; sodium bicarbonate alkalinises urine and increases renal excretion of aspirin

Question 10

Serotonin syndrome diagnosis?

Answer 10

three of: agitation, ataxia, sweating, diarrhoea, fever, shivering