Pharm intro.
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| Pharmacokinetics | Drug movement into, within and out of the body
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| Pharmacodynamics | Drug actions and their mechanisms
what it does once it reaches its site of action
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| What happens if a drug becomes charged? | It CANNOT pass a biological membrane
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| absorption | transfer of drugs from site of administration to systemic circualtion
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| Bioavailibility | fraction of an oral dose that appears in systemic circulation
reduces by first pass effect
altered by changes in GI motility
can be reduced by other substances present in the GI tract ex: antacids will inhibit the absorption of a tetracycline
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| distribution | transfer of drugs from systemic circulation to tissues
is effected by: blood flow, pH, blood-brain barrier, and tissue factors
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| elimination | clearance; removal of drug from the body
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| metabolism of drugs mainly done by? | LIVER
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| excretion is done by? | renal and/or hepatobiliary systems
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| First pass effect | liver metabolizes a lot of drug before reaching systemic circulation if taken orally
some drugs have higher first pass effect than others ex: morphine does not work orally, must be IV
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| Primary means by which drugs transfer across the cell membrane is? | passive diffusion
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| Which drugs can pass through these membranes? | low molecular weight
both lipid and water soluble --> must be WEAK acid or base
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| pH = pKa | then there are equal amounts of charged and uncharged particles (ideal)
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| pH > pKa | BH+ < B favors absorption (both solutions basic)
AH < A- no absorption
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| pH < pKa | BH+ > B no absorption
AH > A- favors absorption (both solutions acidic)
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| Filtration | passage of molecules through pores or porous structures
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| transport mechanisms | drug combines with a transport protein in the membrane and the complex can move across the membrane together
usually happens with highly polar drugs or charged drugs
facilitated diffusion
active diffusion (requires energy)
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| Presystemic absorption | gut and liver (oral)
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| Systemic absorption | IM, IV, subQ, kidney, etc.
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| Enteral | GI tract administration
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| paranteral | needle administration
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| patches | have loading doses and the skin becomes saturated so the patient has to move the next patch elsewhere to avoid over dosing
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| topical | used to treat something locally
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| plasma protein binding | protein bound drug CANNOT distribute to tissues or be eliminated
becomes "pharmacologically inactive"
one drug can displace another; heavily bound protein drugs have high affinity
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| does protein binding effect absorption? | NO!
binding occurs AFTER absorption but BEFORE distribution
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| How does edema or swelling effect anesthetics? | will change blood pH and make anesthetics INEFFECTIVE
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| Biotransformation | elimination/metabolism
conversion of drug to different chemical structure
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| what is responsible for bio-transformation? | mainly the liver via a system of enzymes called the cytochrome P450 (CYP) system
these enzymes are responsible for phase 1 and phase 2 rxns
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| phase 1 rxn | oxidation/reduction rxn by oxygenases and reductases
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| phase 2 rxn | formation of conjugates by transferases; drugs are conjugated with a sugar, an amino acid, or a sulfate
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| Bio-transformation relative to parent compound | metabolite is MORE water soluble
may be more or less active
may be inactive
may be more or less toxic
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| prodrugs | INACTIVE until converted to active form by metabolism (through bio-transformation)
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| Do all drugs go through both phases? | NO; some may even go through the phases backwards
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| Hepatic elimination | secretion into bile and small intestines
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| Enterohepatic recycling | drug conjugate secreted into the bile and reconverted to parent compound by intestinal bacteria which can then be reabsorbed by the small intestines
alteration of bacterial flora can affect the action of some drugs
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| Renal elimination | glomerular filtration
tubular secretion of organic acids and bases
drugs can passively diffuse from tubular cells into the urine and back into the blood stream --> recycling
pH of urine and pKa of drug is important
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| How do you increase elimination of weak acids? | Alkalize the urine by administering bicarbonate or use a diuretic such as acetazolamide which increase bicarb
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| How do you increase elimination of weak bases? | Acidify the urine by administering ammonium chloride
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| First order elimination | VAST MAJORITY
constant percentage of drug eliminated per unit time
50%/4hrs
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| plasma 1/2 life | time necessary to reduce plasma levels of drug my one-half
4-5 half lives for therapeutic drugs and 4-5 half lives for elimination
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| capacity limited (zero order) elimination | constant amount of drug eliminated per unit time
50mg/4hrs
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| Receptors | regulatory proteins that interact with a drug or hormone and intiate a cellular response
basis for classifying drugs: beta-2 agonists, beta antagonists, muscarinic agonists/antagonists
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| what type of receptor do most drugs work through? | G-coupled protein receptor
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| Agonists | affinity and efficacy
can bind AND activate
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| Antagonists | ONLY affinity
can bind but CANNOT activate
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| Tonically active system | antagonist has to constantly block an agonist for there to be an effect
Ex: vasodilators and beta blockers
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| Full agonists | can produce full response; efficacy = 1
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| partial agonists | produce a response less than that of full agonists; efficacy > 0 but < 1
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| inverse agonists | produce a response less than that of partial; efficacy < 0
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| Dose response curves | interactions between agonists and receptors are typically characterized by this
sigmoidal or S shaped
higher effects higher dosage
used to determine ED50
can also determine max respoonse
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| ED50 | does that produces 1/2 max response
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| Competitive anatagonists | block binding by an agonists to its receptor
blockade can be overcome
reduces POTENCY of agonists
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| NON-competitive anatagonists | block binding by an agonists to its receptor
blockade CANNOT be overcome
reduces EFFICACY of agonists
form covalent bond with receptor; must be destroyed and body needs to form new receptor
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| orthosteric | interaction at single site
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| allosteric | binding at one site effects the binding at another site
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| Indicies of safety | bigger the number in the numerator, the safer the drug
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| biologics are composed of? | vaccines, allergenics, blood and blood components, somatic cells, gene therapy, tissues, etc.
can be composed of sugars, proteins, nucleic acids or complex combos of the 3
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| what are biologics? what do they do? | genetically-engineered proteins derived from human genes
most are designed to inhibit specific components of the immune system
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| do biologics follow the same dynamics as small molecule drugs? | NO; most are anti-body based thus follow the rules of immunology
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