Wk 1-2: Pharmacokinetics, Pharmacodynamics, Pharmacogenomics Flashcards
Affinity
Affinity: The attraction between a drug and a receptor.
Allosteric site:
Allosteric site: A binding site for substrates not active in initiating a response; a substrate that binds to an allosteric site may induce a conformational change in the structure of the active site, rendering it more or less susceptible to response from a substrate.
Bioavailability (F):
Bioavailability (F): The fraction or percentage of a drug that reaches the systemic circulation.
F = quantity of drug reaching systemic circulation / quantity of drug administered
Biotransformation:
Biotransformation: Metabolism or degradation of a drug from an active form to an inactive form.
Chirality:
Chirality: Special configuration or shape of a drug; most drugs exist in two shapes.
Clearance:
Clearance: Removal of a drug from the plasma or organs.
Downregulation:
Downregulation: Decreased availability of drug receptors.
Enantiomer (also called isomer)
Enantiomer (also called isomer): A mirror-image spatial arrangement, or shape, of a drug that suits it for binding with a drug receptor.
Enterohepatic recirculation:
Enterohepatic recirculation: The process by which a drug excreted in the bile flows into the gastrointestinal tract, where it is reabsorbed and returned to the general circulation.
First-pass effect:
First-pass effect: The phenomenon by which a drug first passes through the liver where it may be degraded before distribution to the tissues.
Half-life (t1⁄2):
Half-life (t1⁄2): The time required for half of a total drug amount to be eliminated from the body.
Hepatic extraction ratio:
Hepatic extraction ratio: A comparison of the percentage of drug extracted and the percentage of drug remaining active after metabolism in the liver.
Ligand:
Ligand: Any chemical, endogenous or exogenous, that interacts with a receptor.
Pharmacodynamics:
Pharmacodynamics: Processes through which drugs affect the body.
Pharmacokinetics:
Pharmacokinetics: Processes through which the body affects drugs.
Prodrug:
Prodrug: A drug that is transformed from an inactive parent drug into an active metabolite; in effect, a precursor to the active drug.
Receptor:
Receptor: The site of drug action.
Second messenger:
Second messenger: A chemical produced intracellularly in response to a receptor signal; this second messenger initiates a change in the intracellular response.
Therapeutic window:
Therapeutic window: The range of drug concentration in the blood between a minimally effective level and a toxic level.
Threshold:
Threshold: The level below which a drug exerts little to no therapeutic effect and above which a drug produces a therapeutic effect at the site of action.
Upregulation:
Upregulation: Increased availability of receptors.
Volume of distribution (Vd):
Volume of distribution (Vd): The extent of distribution of a drug in the body.
High hepatic extraction ratio = ___ oral bioavailability
High hepatic extraction ratio = low oral bioavailability
Low hepatic extraction ratio = ___ oral bioavailability
Low hepatic extraction ratio = high oral bioavailability
Drugs w/ low hepatic extraction ratio <30%
Barbiturates diazepam warfarin theophylline tolbutamide
Drugs w/ high hepatic extraction ratio >70% include…
lidocaine
meperidine
imipramine
Apparent Volume of Distribution
Vd = Amt in body / Plasma drug concentration
Name a drug that is not metabolized at all
gentamicin (Garamycin)
Prodrug allopurinol metabolizes into
oxypurinol
Prodrug codeine metabolizes into
morphine
Prodrug enalapril metabolizes into
enalaprilat
Prodrug prednisone metabolizes into
Prednisolone
Prodrug valacyclovir metabolizes into
Acyclovir
first-order kinetics
the actual amount of drug eliminated is proportional to the concentration of the drug (the more drug there is, the faster it is eliminated). This applies to most drugs
zero-order kinetics
Fixed amounts of drugs, rather than a fractional proportion, are eliminated at a constant rate
Example: alcohol
This can be dangerous
Pharmacodynamics refers to:
the set of processes by which drugs produce specific biochemical or physiologic changes in the body
Four types of receptors:
gated ion channels
transmembranous receptors
G protein– coupled receptors (GPCR)
intracellular receptors
Foods with tyramine (fermented cheese, wine…) should not be taken with _____ to avoid _______.
MAOIs, hypertensive crisis
Pharmacogenomics
Role of genetic variation in drug response
Genetics may account for ___ to ___ % of variability in drug disposition and effects.
20 to 95%
Adverse Drug Related Events account for (% admissions, total deaths)…
3 to 10% of hospital admissions and prolonged hospital stays, and 100,000 deaths annually
___% DNA accounts for individual differences/variances in drug metabolism and response
0.1%
Allele:
any of the alternative forms of a gene occurring at a specific location on specific chromosome
Genotype:
internally coded, inheritable info in the organism; combination of 2 alleles at single locus
Phenotype:
a measurable trait or characteristic
SNP: Single nucleotide polymorphism…
Variation in a DNA sequence the occurs when single nucleotide (Adenine, Thymine, Cytosine, Guanine) differs among members of a population.
Polymorphisms
DNA variants that occur within a specific population at a frequency rate higher than 1%
The focus of pharmacogenomics are…
…SNPs/Polymorphisms
Substrate:
A drug that binds to and is metabolized by an enzyme
Enzyme:
catalysts that cause oxidation, reduction or hydrolysis of drug
Enzyme Inducer:
molecule (drug) that speeds up the production of an enzyme
Enzyme Inhibitor:
molecule (drug) that slows down or inhibits the production of an enzyme
Inducer/Inhibitor can include
…the drug itself, a second drug, food (grapefruit juice, kale)…
Genetic variants effect proteins how?
Genetic variants translate into functional changes in proteins
More than ___ families of drug metabolizing enzymes in humans
30
Pt without pseudocholinesterase will be unable to break down _______ and could face complications of _______ including ________ as a result.
succinylcholine, prolonged paralysis and apnea
Common efflux protein
P-glycoprotein
Transport proteins like P-glycoprotein are thought to be ______ against toxins in food, etc
Protective
P-gp controls ATP-dependent _____ _____ of ______
cellular efflux of substrates, anticancer drugs, immunosuppressive drugs, and other meds
A LOW expression of gene for P-gp will result in…
…higher drug levels. Less P-gp = more drug in circulation.
P-gp associated with lower ___ drug concentrations
HIV
Protease inhibitors for HIV (indinavir, nelfinavir, etc…) have ___ bioavailability due to P-glycoprotein
Variable or low
Pt’s with low expression of P-gp have ______ plasma concentrations of HIV antivirals
2-5 times
P-gp is expressed in these places:
GI tract, CNS
___% of drugs marketed in US metabolized by cytochrome 450 / CYP450
70%
CYP450 inhibited by these types of foods
Grapefruit juice, charred foods, kale / cruciferous vegetables
CYP450 highest levels in this organ _____ but also found in this organ ____
liver, GI tract
P-gp is found in ______ and also in ____ and _____
intestine (transfers back to intestine), also in liver and kidney (transfers to bile and urine)
The drug ______ INHIBITS intestinal P-gp and renal P-gp, leading to ____ levels of digoxin
Quinidine; increases ABSORPTION of digoxin in intestine, and decreases ELIMINATION of digoxin at kidney
The antibiotic drug ________ has this effect on P-gp, and digoxin.
Rifampin induces intestinal P-gp, decreases digoxin absorption, lowering serum concentrations
Alcohol can _______ CYP enzymes leading to ____ serum levels of drug
inhibit, increase …(hypoglycemia in pt’s taking insulin
Metronidazole inhibits enzyme ______, which increases ____ and leads to ______-like reaction
inhibits aldehyde dihydrogenase
elevates acetaldehyde
causes disulfiram-like reaction (flushing, h/a, n/v, hypotension, blurred vision)