Pharmacodynamics Flashcards
What is the half-life of a drug?
-the time that it takes for the concentration of the drug in the bloodstream to decrease by half
-can range from minutes to hours
What does the half-life of a drug determine?
-when repeat dosing is required to maintain its therapeutic levels
Do drugs with very short half-life’s maintain their therapeutic effect for long?
No
Usually need to be given more frequently
What causes toxicity in reference to half-life of drugs?
-if drugs are administered too frequently or soon increasing the blood concentrations
What is the therapeutic range?
-the range of drug concentrations in the plasma or blood that produce the desired therapeutic effects of the target cells/tissues with minimum adverse effects
What is a drugs therapeutic index?
-calculated in the research and development phase of the drug production
-used to determine how beneficial the drug is in relation to the toxic effects it may have
-the ratio of toxic dose to the therapeutic dose
What is steady state concentration?
-the point at which, following repeated (or continuous) doses of the medicine a consistent steady level of the drug is present in the animals plasma
What does the term steady state mean?
-an equilibrium level of drugs is established for long term medications
-this is a plateau where the intake of the drug matches the elimination
What is the rule of 5?
-it takes 5 half life’s to reach the steady state and functional elimination
What are adverse drug effects?
-more harmful
-more unexpected than side effects
What are adverse events?
-occur when a medication is administered correctly
What are side effects?
-more predictable
-can be beneficial or harmful
-secondary unwanted effects due to drug therapy
What are receptor mediated drugs?
-drugs that exert their therapeutic effects by binding to cellular receptors in their target organ or tissues
What are non-receptor mediated drugs?
-drugs that produce an effect without combing with receptors
How do drugs work?
-for cells to respond to a drug molecule, usually the drug must combine with a receptor, which is a specific protein molecule on or in a cell
-a given receptor only combines with the molecule of certain drugs based on their shape or molecule structure
-this concept may be compared with a lock and key, the receptor is the lock into which only the correct key (the drug) will fit (produce an effect)
What does the lock and key term mean in relation to drugs?
-the most potent or effective drugs at a receptor will be one that fits perfectly
-other drugs may fit less perfectly and may exert a partial effect
What are agonists?
-drugs that combine with and activate a receptor to stimulate the desired response
-they can produce a maximum effect if given in high doses
What is an example of an agonist?
-methadone
-full agonist opioid
-binds full to ų receptors to provide a potent analgesic effect
What is a partial agonist?
-drugs which have a less than perfect fit to the receptors meaning they may only partially stimulate a response
What is an example of a partial agonist?
-buprenorphine
-partial agonist opioid
-binds to ų receptors but doesn’t achieve potent analgesia
Can buprenorphine produce a maximal response?
-no
-increasing the dose doesn’t increase the therapeutic effect but rather reaches an analgesic plateau
What happens if a partial agonist is administered alongside a full agonist?
-it may displace the receptor binding of the full agonists and reduce their analgesic efficacy
What is an antagonist?
-drugs which interact with receptors to inhibit the action of an agonist without initiating any effect themselves
-they block the access of the agonist to the receptor
What is an example of an antagonist?
-naloxone
-pure opioid antagonist
-binds to all types of opioid receptors in the body
-can reverse the effects of opioid administration
