Pharmacodynamics Flashcards
(52 cards)
What is pharmacokinetic tolerance?
Response is decreased due to drug being broken down before it gets to the target sites - Drug levels change
What is pharmacodynamic tolerance?
Response is decreased due to changes in receptor number or function
- Drug levels do NOT change
What is physiological tolerance? Provide an example.
When two agents with opposing physiological effects are administered together
- Histamines cause vasodilation while epinephrine causes vasoconstriction
What are the four factors that influence the variability in drug response?
- Differences in drug absorption
- Differences in ligand concentrations
- Differences in number/function of receptors
- Differences in post receptor effects
What is summation?
Two drugs elicit a similar response through different mechanisms; effect equals the sum of the two individual effects
What is synergism?
Two drugs elicit a similar response through different mechanisms; effect is greater than the sum of the two individual effects
Compare additive effect to summation effect
- Summation: two drugs work through different mechanisms
- Additive: two drugs work through the same mechanism
What is organ-directed toxicity? Provide two examples.
Drugs are toxic to organs/tissue that have no involvement in therapeutic effect
- Tylenol and liver issues
- Tetracyclines and teeth discoloration, less bone growth
What is tachyphylaxis? Provide an example.
Rapid development of tolerance following repeated doses over a short period of time
- Meth (aka stimulants)
What does the administration of antagonists do?
Causes up-regulation (more receptors due to prolonged presence of antagonist)
What is an example of metabolic enzyme deficiency?
Succinylcholine in patient’s with low serum cholinesterase
- Cholinesterase degrades succinylcholine but if it is deficient, the succinylcholine will remain in the plasma longer - 4 minutes of sedation turns into 4 hours
What is an example of competition for plasma binding sites?
Warfarin and Phenytoin
- When both are present, they compete for the same binding sites so Phenytoin can displace Warfarin and it will remain free (active) for longer → Warfarin dose must be reduced to avoid toxicity
What are six examples of “acceptable” adverse effects?
- Headache
- Fatigue
- Dizziness
- Upset GI
- Nausea
- Vomiting
What is overextension-type toxicity? Provide an example
Basically overdosing…
- Example is Warfarin causing hemorrhage
Provide three examples of organ-directed toxicity.
- Aminoglycoside antibiotics and ototoxicity
- Acetaminophen and hepatotoxicity
- Metabolite toxicity: Acetaminophen and Isoniazid hepatotoxicity
What is often the cause of an idiosyncratic drug response?
Mutation (polymorphism)
With drug allergies, what type of response is activated?
Immunologic response
What type of a response is Type I? How is this mediated? Provide an example.
Anaphylactic
- IgE antibody-mediated
- Ex. Penicillin-induced anaphylaxis
What type of a response is Type II? How is this mediated? What does this result in?
Cytotoxic
- IgM or IgG antibody-mediated
- Results in RBC lysis
What type of a response is Type III? How is this mediated? Provide an example.
Immune Complex (Arthus)
- Antigen antibody-mediated
- Ex. serum sickness
What type of a response is Type IV? How is this mediated? Provide an example.
Delayed Hypersensitivity
- Cell-mediated
- Ex. SJS or Erythema Multiforme
Differentiate between up regulation and down regulation.
Up-regulation: increase in number of receptors in order to increase response
Down-regulation: decrease in number of receptors in order to decrease response
What is covalent binding? Provide an example.
Strong, IRREVERSIBLE bonding
- Ex. Aspirin
Differentiate between the efficacy of full agonists, partial agonists and antagonists.
Also consider affinity…
- Full agonists have affinity and efficacy (a = 1)
- Partial agonists have affinity but lower efficacy (0 < a < 1)
- Antagonists have affinity but no efficacy (a = 0)
