Test #2 Flashcards
What the body does to the drug
Pharmacokinetics
What the drug does to the body
Pharmacodynamics
Area of pharmacology concerned w/ unusual response to drugs caused by genetic differences b/w individuals
Pharmacogenetics
Repetitive sequence of experimentation & characterization involving biologic assays ranging from the molecular to organism level
Drug screening
What is the end result of drug screening process called?
Lead compound (a patentable entity)
What is the goal of preclinical studies?
Identifying potential human toxicities & designing mechanism to monitor for these toxicities in clinical trials
What are the 3 types of toxic doses?
- No effect: max dose showing no toxicity
- Min. lethal dose: min. dose that kills a subject
- Median lethal dose: kills 1/2 of test subjects
What are some limitations of preclinical testing?
- toxicity testing is time consuming & expensive
- Large numbers of animal subjects needed
- Extrapolation of animal data to humans may not be accurate
- Rare adverse effects are unlikely to be detected
What are 5 confounding factors in clinical trials?
- Most ds’s have a variable clinical course
- Presence of other ds & risk factors
- Known & unknown ds/risk factors may influence clinical study results
- Subject & observer bias
- Study design must account for placebo effect
The administrative body charged w/ oversight of the drug evaluation process.
FDA
These trials determine the dose-response relationship of the drug. Subjects are normally healthy volunteers. The main goal is to identify the maximal tolerated dose in the absence of severe toxicity. Pharmacokinetic parameters are determined in these trials
Phase I trials
During these trials, the drug is studied in a small group of pts w/ the target ds to detemine efficacy. A single blinded protocol is usually used.
Phase II trials
These trials try to establish safety & efficacy. These trials are designed to minimize potential confounding factors. Often involve double-blind crossover protocols.
Phase III Trials
These trials involve monitoring drug safety when used by a large number of pts. This relies on the voluntary, timely, & complete reporting of toxicity by prescribers
Phase IV trials
This Act provided incentives for the investigation & development of drugs for rare ds’s
Orphan Drug Act of 1983
A reaction to a drug that is harmful or an unintended response. Claimed to be the 4th leading cause of death in the US
Adverse Drug reactions
A fundamental principle of pharmcodynamics is that drugs only modify what?
Normal biochemical & physiologic processes; they don’t endow new capabilities
The pharmacologic effect is mediated through what?
Drug/receptor binding
The most biologically important & common receptors are __________ that bind extracellular molecules (ligands) which results in an intracellular change (transduction).
Integral membrane proteins
What are the 4 major types of integral membrane proteins?
- Ligand gated ion channels
- G-protein coupled receptors
- Enzyme-linked receptors
- Intracellular receptors
These channels are responsible for regulation of the flow of ions through the cell membrane. Respond rapidly & have a very short duration of effect. Can open channels or modify the function of ion channels.
Ligand gated ion channels
Voltage gated ion channels in peripheral nerves are receptor sites for what type of drugs?
Local anesthetics
Ligand binding to the extracellular receptor site of a G-protein couple receptor leads to what?
Activation of the alpha-subunit of the G-protein, the release of bound GDP, & binding of a GTP
Stimulation of G-protein coupled receptors results in responses lasting how long?
Seconds to minutes
Enzyme-linked receptors elicit responses that last how long?
Minutes to hours
What is the M/C enzyme type assoc. w/ enzyme-linked receptors?
Tyrosine kinase
These hormones pass directly through the cell membrane binding to an intranuclear receptor
Steroid hormones (receptor-steroid complex binds to DNA segment causing altered gene expression)
Intracellular receptors elicit responses that can last for how long?
at least 30 minutes but can last for hours to days (b/c it involves new protein synthesis)
Binding of a small number of receptors can dramatically alter total cellular metabolism due to what?
Cascade effect
Repeated or continous administration of an agonist (or antagonist) may lead to changes in receptor population & thereby responsiveness leading to what?
Receptor desensitization (to protect cell from damage)
Normal cytosolic proteins that recognize agonist-activated, phosphorylated receptors & bind them.
Arrestins (binding makes receptor inaccessible for G-proteins)
The magnitude of a drugs effect depends on what?
Concentration at the receptor site which is determined by the dose of the drug & the drugs particular pharmacokinetics
As the drug’s concentration increases the magnitude of the pharmacologic effect increases. This is called what?
Graded dose response
A plateau in the drug’s effect is reached when what happens?
- All receptors are occupied
2. For receptors w/ a large “spare” population maximal cellular response is attained
This is the amount of drug necessary to produce an effect 50% of an agent’s max. effect.
Potency
A significant contributing factor to potency is what?
Affinity of a drug for the receptor
The ability of an agent to produce an effect of a given magnitude, the max. biologic response to a drug.
Efficacy
If a drug binds to a receptor & produces a biologic effect that mimics the response of the endogenous ligand it is called what?
Agonist (ex: phenylephrine –> epinephrine; meth –> MAO enzymes)
These are drugs which decrease the response of another drug or endogenous ligand.
Antagoinsts
What are 4 mechanisms by which antagonists work?
- Bind to same receptor site as agonists (blocking)
- Non competitive (allosteric inhibition); bind to different site causing a conformational change
- Irreversible binds a receptors (ex: ASA –> COX-1)
- Chemical antagonists; bind w/ another drug making it inactive (ex: Protamine sulfate –> heparin)
These drugs have some intrinsic activity by it’s less than a full agonist.
Partial antagonists (partial agonists) (Ex: Pentazocine –> morphine; methadone)
When a drug binds to a separate receptor but the response opposes the response to an agonist
Functional (Physiologic) antagonism (Ex: epinephrine –> histamine)
Type of agonist that inhibits receptors that are active in the absence of an agonist
Inverse agonist (seen in benzodiazepine & cannabinoid receptors)
These are used to determine the ability of a drug to produce a response of a predetermined magnitude in a pt population. Useful in determining toxic dose in populations
Quantal Dose-Responses
The ratio of the dose that produces toxicity to the dose that produces the desired response
Therapeutic Index
A large Therapeutic Index indicates what?
Toxicity requires a much larger dose than required for the desired effect.(penicillin)
What does a small Therapeutic Index indicate?
The dose for the therapeutic effect approaches the toxic dose, these drugs are potentially dangerous.(warfarin)
Attempts to explain an unexpected drug response via a genetic mechanism. Goal is to understand the role that genetic make-up in responses to drugs, both therapeutic & toxic responses
Pharmacogenetics
Identifies genetic differences w/i a population to try to explain observed responses or susceptibilities to drugs or ds processes
Pharmacogenomics
What are some characteristics of all anti-anxiety agents?
- Have sedative properties (hypnotics)
- Many possess anticonvulsant properties
- Able to induce anterograde amnesia
- Most potentiate GABA activity