PHM 338 Quiz 2

partial agonist

* increasing concentrations of agonist will produce an increase in biologic effect up to an intrinsic activity < 1

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* all receptors bound → activity level < 100%

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* can be used therapeutically for withdrawal symptoms

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* ex. methadone

antagonism

binding of a drug to a receptor that does NOT activate the receptor and prevents a response to an agonist

noncompetitive antagonism

* block can NOT be overcome by increasing dose of agonist
* aka “irreversible antagonist”
* no activity
* ex. naloxone

competitive antagonism

* block can be overcome by increasing the dose of the agonist
* agonist can be reversed (usually by flooding with agonists)

pharmacologic antagonism

* competitive & noncompetitive antagonism
* based on one effect on the same receptor

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ex. drug A ↑ HR by binding to receptors in heart, but drug B ↓ HR by blocking drug A from reaching receptors

effect antagonism

* 2 receptors are working, but the EFFECTS/ACTIONS oppose each other
* based on 2 effects on different receptors

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ex. drug A ↑ BP in brain, drug B ↓ BP in arm

ligand-gated ion channels

ligand binds to active site → conformational change → drugs can manipulate how long channels stay open

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ex. acetylcholine agonist keeps channel open longer

enzymes

proteins that speed up chemical reactions

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can cause conformational change by binding 2 molecules together

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ex. renin → ANG I → ANG II can be done faster with use of these

oral drugs

most common dosage form

enteral administration

most common route of administration

mouth

* enteral administration
* thin lining, rich blood supply
* sublingual and buccal routes

stomach

* enteral administration
* medium surface area, rich blood supply, acidic pH
* drugs don’t stay here long

small intenstine

* enteral administration
* huge surface area, rich blood supply, basic pH

rectal

* enteral administration
* small surface area, rich blood supply, basic pH
* inconvenient but advantageous for local activity, if pt is unable to swallow

parenteral administration

advantages:

* can be used for drugs that are poorly absorbed
* provide an immediate onset of action
* provide a longer lasting effect
* can concentrate drug at a specific location
* provide a more predictable response
* provide titratable dosage

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disadvantages:

* pain
* irreversible
* extravasation (toxic chemical leak into tissue)/phlebitis (vein inflammation)
* not useful for self-admin
* contamination/infection

intravenous, intra-arterial, intramuscular, epidural, intrathecal, subcutaneous, intra-articular

types of parenteral administration

skin

topical administration

* ointments, creams, patches
* local and systemic

eyes

topical administration

* drops, ointments
* local distribution

ears

topical administration

* local distribution

intranasal

topical administration

* spray and drops
* local and systemic

inhalation

topical administration

* local and systemic
* local: asthma, COPD
* systemic: anesthesia

vaginal

topical administration

* local and systemic
* mainly local, can be systemic for hormones

disintegration

1st pharmaceutical phase of tablets

* tablet hits fluid → breaks into little chunks to increase surface area

dissolution

2nd pharmaceutical phase of tablets

* broken into molecules, can be absorbed

dissolved liquid

oral dosage form

* ex. elixir, syrup
* not convenient compared to tablets

suspensions

oral dosage form

* chunks of drug floating in liquid (must shake)
* thick, gloopy

powders

oral dosage form

* ground up drug
* not common, inconvenient

capsules

oral dosage form

* gelatin shell containing powder

tablets

oral dosage form

* compressed powder (made w/ pressure)

coated tablets

oral dosage form

* coating for extended release, easier swallowing, taste

enteric-coating

oral dosage form

* specific coating made to survive stomach acid, only dissolves in basic pH

sustained-release

oral dosage form

* a short-term drug turned into a longer-lasting drug

dissolved liquid

fastest absorbed oral dosage form

sustained-release

slowest absorbed oral dosage form

rate

_____ of absorption can determine

* onset of action
* duration of action
* intensity of response

variables affecting absorption

* nature of absorbing surface
* surface area
* blood flow to site of administration
* pH at the site of absorption

primary method of excretion

kidneys

drug elimination

2 types:


1. biotransformation
2. excretion

biotransformation

active drugs transformed into inactive for elimination

hepatic metabolism, tissue enzymes

types of biotransformation

secondary method of excretion

GI tract

absorption phase

absorption rate more than elimination rate

elimination phase

no significant absorption occurs

toxic level

concentration of drug that will predictably cause problems

minimum effective concentration

how much drug in the body before there is an effective concentration

therapeutic range

safe and effective concentration of drugs in the body

onset of action

time for drug to become effective

body weight

variable affecting dose/response

* larger doses often given to patients with greater weight or BMI
* dependent on where drug is distributed to

age

variable affecting dose/response

* altered capacity to metabolize and/or excrete drugs (usually decreased)
* most common in very young and very old

gender

variable affecting dose/response

* differences in body composition and hormonal activity

genetics

variable affecting dose/response

* enzymatic differences can lead to alterations in magnitude or effect
* decrease or increase

tolerance

variable affecting dose/response

* larger doses must be given to maintain the same effect
* commonly seen with opioids

psychological factors/beliefs

variable affecting dose/response

* placebo effect

comorbid medical conditions

variable affecting dose/response

* can affect all phases of pharmacokinetic and pharmacodynamic response

drug-drug interaction

pharmacological or clinical response to the administration of a drug combination difference from that anticipated from the known effects of the two agents when given alone

synergism

one drug enhances the effect of other drugs

pharmacokinetic

* drug interaction in which one drug alters the rate or extent of absorption, distribution, metabolism or excretion of another drug


* one drug causes a change in the plasma concentrations of another drug

pharmacodynamic

* drug interaction in which one drug induces a change in a pt’s response to a drug without altering the object drug’s kinetics
* pharmacological interactions

pharmaceutical

* drug interaction that includes physical and chemical incompatibilities
* IV admixtures

pts at greatest risk of interactions

pts on multiple medications, multiple prescribers/pharmacies, elderly, obese pts, critically ill pts

object drug

drug for which an effect is altered (increased or decreased)

precipitant drug

drug that provokes an interaction onto an object drug

narrow therapeutic range, steep dose response curve, metabolized by hepatic enzymes, typically used chronically

characteristics of important object drugs

small intestine

primary site of drug absorption

complexation

drugs that form chemical complexes with other agents may lower the rate and extent of drug absorption

* ex. divalent and trivalent metal ions; Mg, Ca, Zn, Fe, Al can bind to prescription drugs and prevent absorption

complexation, changes in pH, changes in GI motility

mechanisms of altered absorption

H2 receptor blockers, proton pump inhibitors, antacids

drugs that can change gastric pH (acidic to basic)

ketoconazole, itraconazole, iron supplements

drugs that need an acid pH for dissolution