Ch. 6: Drug Interactions

Question 1

Drug-Drug Interactions

Answer 1

• intensification of effects: increased therapeutic effects and increased adverse effects
• reduction of effects: inhibitory (result in reduced drug effects), reduced adverse effects, reduced therapeutic effects
• creation of a unique response

Question 2

Basic Mechanism

Answer 2

• direct chemical or physical interaction: never combine drugs in the same contanier without establishing compatibility (most common in IV solution)
• pharmacokinetic: altered absorption, distribution, renal excretion, metabolism, cytochrome P450 group enzymes
• pharmacodynamic: at same receptor= inhibitory; at separate sites= potentiative or inhibitory
• combined toxicity: with overlapping toxicities should not be used together

Question 3

Pharmacokinetic Interactions

Answer 3

• absorption: elevated gastric pH, laxatives, depress peristalsis, induce vomiting, adsorbent drugs, reduce regional blood flow
• distribution: competition for protein binding, alteration of extracellular pH
• renal excretion
• metabolism: most imoprtant and complex mechanism
  cytochrome P450 group enzymes: inducing agents, inhibition of CYP isoenxymes (usually undesired)

Question 4

P-glycoproteins

Answer 4

• transmembrane protein that transports a wide variety of drugs out of cell
• reduce or increase PGP

Question 5

Drug-Food Interactions

Answer 5

• absorption: extent (milk and tetracycline, fiber and digoxin)
• increased absorption: high-calorie meal and saquinavir; without food, not enough is absorbed
• metabolism: grapefruit inhibits and raises drug blood levels

Question 6

Drug-Herb Interactions

Answer 6

• reliable info is lacking

ex. St. John’s wort induces drug-metabolizing enzymes and reduces blood levels of many drugs