Drug interactions Flashcards
What is an example of enzyme induction
Induction - drugs increasing activity of enzymes leading to decreased levels and efficacy of the drugs.
Rifampicin induces CYP3A4 which can decrease the effectives of oral contraceptives
What is an example of enzyme inhibiton
Some drugs inhibit these enzymes, resulting in increased levels of the affected drugs, potentially causing toxicity. For instance, ketoconazole inhibits CYP3A4, which can increase the levels of certain statins, leading to a higher risk of side effects like muscle toxicity.
Give an example of changes in GI tract motility and pH
Antacids increase the pH of the stomach affecting absorption of ketoconazole which requires acidic environment for absorption
What is chelation? Give an example
Binding of one drug to another forming an insoluble complex that cannot be absorbed
Tetracycline abx form chelates with calcium or iron supplements reducing the absorption and effectiveness of abx
How does competition for renal tubular transport affect drugs? give an example
Drugs can compete for the same renal transport mechanisms affecting each others excretion rates
For example, probenecid can compete with penicillin for renal tubular secretion, prolonging the action of penicillin by reducing its excretion.
How does changes in protein binding affect drugs ? give example
Some drugs can displace others from their binding sites on plasma proteins, increasing the free (active) concentration of the displaced drugs. For example, warfarin is highly protein-bound, and its displacement by another drug can increase the risk of bleeding.
What is synergism? give example
Combined effect of 2 drugs is greater than the sum of their individual effects
E.G. aspirin and clopidogrel results in greater antiplatelet effect than the drug alone
What is antagonism
When one drug reduces of blocks the effect of another
What is allosteric modulation
Drug binds to a site on a receptor that is different from the active site (allosteric site). The binding can change the receptor’s shape and activity.
What is positive allosteric modulation. Give example
When binding at an allosteric site results in enhanced effect of the primary ligand
Benzos act as PAMs at the GABA-A receptor, increasing the effect of GABA resulting in sedative and anxiolytic effects
What is a negative allosteric modulator, give an example.
These inhibit the effects of the primary ligand. For example, some experimental drugs that act as NAMs at the mGluR5 receptor are being studied for the treatment of disorders like anxiety and depression by dampening overactive glutamatergic signalling.
