PHARM Block 1 Flashcards
Pharmacology
The science of drug action on biological systems
Pharmaco = medicine / drug
logy = study
Pharmacy
clinical practice devoted to the formulation, proper and safe distribution and use of drug
Pharmaceutical Drug
chemical substance for medical diagnosis, treatment, or prevention of disease
Discuss the first recordings of drug action
China: Chen Nog in 200 B.C was a divine farmer and Chinese herbal medicine
Egypt: The book of Thoth is the world’s oldest preserved medical and pharmacological record
What did Galen introduce
The study of anatomy and described the actions of agonists and antagonist
During the Islamic Golden Age, scientists developed an understanding of
drug quantities and formulations
Who is Swiss-German physician-scholar Paracelsus
The father of toxicology, the dose makes the poison
Who is William Withering and what is his connection to Tucson
An English botanist that discovered digitalis treat congestive heart failure
digitalis (fox glove) is native to Tucson
but if you use the Nerium oleander then it is poisonous to humans
What did the Lewis and Clark expedition discover
willow bark tea to treat fever and pains because salicilin is metabolized to aspirin
Who is Friedrich Serturner
Isolated alkaloid from opium and over dosed
named morphine from the Greek god of dreams, Morpheus
Who is Friedrich Wohler
founded synthetic organic chemistry
Who is Hippocrates
The Father of Western Medicine and began the separation of medicine from religion and superstition
Who is Claude Bernard
Founded the concept of homeostasis
Pharmacodynamics
The mechanism of drug action
How do drugs act on receptors
usually proteins which result in a change in the system
What are effectors
molecules that translate the receptor - drug interaction into a change in cellular activity
Discuss the misleading nature of the Lock and Key model of molecular pharmacology
it is not simply turned on or turn off
Instead, think of receptors as fluctuating between favored and disfavored energy states constantly
R*
disfavored, active, high-energy state
R
favored low - energy state
What do agonists do
lower the free energy of the activated state and this will make it more favorable than the baseline state.
*cycling between states still continues
Binding of a ligand can
cause an induce fit which is a conformation shift of the receptor that can cause effector signaling
Are receptors ever completely on or completely off
No, even some imperfect agonists can still stimulate the receptor given enough concentration
Discuss the Saturation Radioligand Binding as a key method for measuring the binding of a drug to a receptor
-Membrane preparation of tissue or cells with target
-Increasing concentrations of radiolabeled drug
-Non‐specific binding component
-Saturating concentrations of cold selective ligand
-Reaction proceeds to equilibrium
-you have your ligand (drug) and it is radiolabled and its going to bind and saturate it (high affinity low capacity systems) and you can use it to measure how well the drug binds to its binding site
Competition Radioligand Binding
A known amount of radiolabeled established drug is competed off of a receptor by a non - radiolabeled drug with unknown affinity
-two drugs competing for a binding site and they compete by affinity and concentration
- the less it takes for the drug to compete away to higher the affinity
*Allosteric sites are a problem
Bmax
Total number of binding sites
Kd
Binding constant (affinity) of the drug
Why do you not want to use Saturation Binding?
Because you do not want to radiolabel a bunch of drugs, therefore you would use Competition Radioligand Binding
IC50
Concentration at 50% inhibition
The data obtained is the IC50. IS this the same as the drug affinity?
No, this is not the drug affinity because if you double the radio labeled drug then you have twice as much drug to compete away .
IC50 is depended upon the concentrations of the two drugs
Ki
Binding Constant (affinity) of our experimental, unlabeled drug
Assumptions of the experiment
-Bound concentration is negligible compared to free
-No binding cooperativity
-At equilibrium
-Binding is reversible and follows Law of Mass Action
Most drug binding to receptors involve
non - covalent interaction with key amino acids
Efficacy
E max
Potency
EC50, ED50
Can a partial agonist be more than a full agonist
A full agonist reaches the maximal response capability of the system, and a partial agonist does not (even at full receptor occupancy)
How are affinity and potency different
Affinity defines the strength of attraction between the drug and its receptor. A high affinity is generally associated with a lower dose requirement (compared to low affinity for the same receptor). Potency describes the relationship between the drug dose and the magnitude of the effect
Can antagonists be competitive and non competitive
Yes, competitive and reversible binding and non competitive is irreversible which will reduce the total amount of receptors available to bind agonist
Antagonists
bind to the target but do not cause a conformation shift , therefore baseline activity is still the same
*cause agonist to not be able to bind so you can only see the effects of an antagonist when an agonist is present
Agonists
a substance which initiates a physiological response when combined with a receptor
Inverse agonists
bind to the receptor, but shift the energy landscape baseline (R) is lower and / or the active state (R*) is higher so the receptor spends even less time in the active state than before
Drug selectivity
Selectivity deals with how well your drug binds to your preferred target vs other targets.
Side effects
“Side effects” can come from both the actions of your drug on its key target and from actions on other targets
Can antagonists be competitive and non competitive
Yes, competitive and reversible binding and non competitive is irreversible which will reduce the total amount of receptors available to bind agonist
Pharmacokinetics
how the body deals with the drug
Important phases of how the drug move in and out of our tissues/bodies
ADME
A= Absorption
D= Distribution
M= Metabolism
E= Excretion
T= Toxicity (sometimes)
Absorption
Many factors influence absorption, especially route of administration.
-I.V. route bypasses most barriers to get to plasma
-Oral -> gut-> liver -> plasma -> kidney -> urine
-All drugs must eventually interact with plasma (central compartment)
-Diffusion can always go both ways between compartments
EX = muscle <-> plasma, gut <-> plasma
Passive transport Verse Active transport
Passive = no ATP, diffusion
Active = Facilitated diffusion, drug transporters
Discuss key characteristics of the drug that affect absorption
lipid solubility
molecular size & weight
pKa
Discuss key characteristics of the tissue that affect absorption
membrane permeability
membrane thickness
pH
local blood flow
local surface area/anatomy
transport mechanisms
Frick’s Law of Diffusion
most drugs move down their concentration gradient (passive diffusion)
How do orally administered drugs move through body?
Must pass through the gut and all blood from the gut passes through the portal vein into the liver before general circulation
- This is an issue because the liver has many CYP’s
Bioavailability
the fraction of drug absorption into the systemic circulation.
AUC (Area under the curve) of plasma concentration verse time for the i.v route compared to that for the test route (oral)
Drug pKa
pH at which 50% of the molecules are ionized
Acids verse Bases
Acids are increasingly ionized in a basic environment, bases increasingly ionized in an acid environment
How does pKa affect drug diffusion
because difference in pH in body fluids an lead to “trapping” of drugs in certain compartments
-this can affect absorption/elimination
-Trapping can help eliminate drugs through the urine
how do you trap a weak base
acidify the urine with ammonium chloride
how do you trap a weak acid
alkalinize the urine with sodium bicarbonate
Distribution
depends on size of the organ, blood flow, solubility, binding
Distribution
depends on size of the organ, blood flow, solubility, binding
Drugs are distributed in different phases
starting with high flow ares then low flow ares
binding to albumin in plasma dramatically affects what
percent of drug available to distribute to tissue
-adding a second albumin-binding drug can change the “bound verse free” percentage of drug 1. This can contribute to drug side effects
How is blood - brain barrier an extra challenge for drug distribution
-Tight junctions between capillary endothelial cells verse fenestrated
-maintains homeostasis and restricts access to toxic xenobiotics / metabolites
Volume of distribution (Vd)
the volume that relates the amount of drug given to the body to the plasma concentration
Vd = amount of drug in body / plasma drug concentration
*if drug distributes throughout the body well Vd is large, if drug stays in plasma Vd is small
What can Vd be used to calculate
therapeutic does by multiplying by plasma concentration (Cp)
Metabolism
biotransformation
this is how the body changes the drug in order to eliminate it
Phase I of metabolism
typically uses Cytochrome P-450 family members to add or expose a functional group on the drug, making it more polar
Phase II of metabolism
conjugates a bulkier functional group onto the drug in order to further increase water solubility and excretion
Several drugs and natural products are known to induce or inhibit the expression/activity of Cyp enzymes. How can
this be a problem?
Cyp enzymes are a group of enzymes encoded by P450 genes and are expressed as membrane bound proteins mostly found in the endoplasmic reticulum of the liver.
-If expressed CyP then this could increase the metabolism of drugs so they never reach receptor
-If inhibited CyP then this could decrease the metabolism of drugs
Excretion
enterohepatic circulation =
conjugated drugs in the liver can be carried in the bile into the gut for excretion
-most drugs excreted through the urine by action of kidneys
-Quantified using renal clearance value (CL)
*high CL = fast clearance
Zero order kinetics
A fixed amount of drug can be handled at one time (alcohol)
First order kinetics
constant fraction of the drug is metabolism per unit of time
-more drug = faster metabolism
Half life
time to excrete half of the drug
Use half-life and kinetics in order to know how to dose patients to achieve steady-state levels of drug.
Typically takes
4-5 half-lives to reach steady-state.
Sex
as a classification, generally as male or female, according to the reproductive organs and functions that derive from the chromosomal complement
Gender
person’s self representation as male or female or how that person is responded to by social institutions on the basis of the individual’s gender presentation
Describe strategies to address gender differences in PK/PD across in vitro to post - approval stages
- Report sex/age of cells/subjects in studies
- Stratify findings by sex and/pr hormone levels
- Dose by weight
- Dose by hormone concentrations / weight or body composition
- Study pharmacogenomics
- study hormone drug interactions
-include aged and pregnant persons
How PK contribute to sex/gender differences
- Drug absorption is influenced by body composition, including body weight, lean mass, free water, and total body fat
- Distribution is impacted by organ size, blood flow, and total plasma volume are lower in female bodies which is coupled to increased resting heart rates and longer OT intervals
- Metabolism/excretion, renal and liver functions is lower in women. Males and females have a different constellation of CYP enzyme
- poly pharmacy
How PK contribute to sex/gender differences
- Hormone fluctuations over life span (In utero through menopause/age matched males)
- Exogenous administration of hormones (Birth control, hormone replacement, gender affirming therapies, lifestyle)
- Formulation responsively, changes in half life
The autonomic nervous system (ANS)
provides involuntary, subconscious regulation of all organs and glands, controlling for example the blood pressure, heart and lung function, digestion, body temperature, metabolism, sweating, pupil size and secretions of certain glands
What does the ANS consists of
-The sympathetic division (SNS) that is activated during the “fight and flight” response to stress
-The parasympathetic division (PSNS) that promotes conservation and restoration of energy “rest and digest” response
Enteric nervous system
works in parallel to the sympathetic and parasympathetic systems to regulate the peristalsis of gut wall and activity of GI tract
What does the anatomical organization of the ANS consists of
preganglionic neurons residing in the CNS that extend to the peripheral peripheral autonomic ganglion where they synapse on postganglionic neurons. Postganglionic neurons innervate the target organ
What do the neurotransmitters of the ANS include
1) acetylcholine, release from all preganglionic neurons and from parasympathetic postganglionic neurons
2) norepinephrine released from sympathetic postganglionic neurons
3)epinephrine released upon sympathetic activation from the adrenal medulla
What do norepinephrine and epinephrine act on what
α and β adrenergic receptors of sympathetic
targets.
Acetylcholine acts on nicotinic ACh receptors on
all postganglionic cells and on muscarinic ACh receptors expressed on target organs of the PSNS
Blood vessels
receive mostly only sympathetic innervation
-Activation of smooth muscle α1-adrenergic receptors causes vasoconstriction.
- Activation of β2-adrenergic receptor in skeletal muscle and liver vasculatures produces vasodilation
Heart
-receives dual sympathetic and parasympathetic innervation with opposing roles.
- Sympathetic stimulation increases the natural pacemaker activity of the heart cells through effects on the ß1 receptors resulting in increased heart rate.
- Parasympathetic stimulation decreases the heart rate through effects on M2 muscarinic receptors
Lungs
- Sympathetic activation increases the diameter of bronchioles (bronchodilation), increasing the air flow.
- Parasympathetic activity produces bronchoconstriction
Eye
- Activation of the M3 muscarinic receptors causes ciliary muscle contraction to accommodate the lens for near vision. There is no significant sympathetic innervation of the ciliary muscle.
- Sympathetic activation constricts the dilator (radial) pupillae muscle of the iris resulting in pupil dilation (mydriasis).
- Parasympathetic activation constricts the sphincter (circular) pupillae muscle causing the pupil to constrict (miosis)
The German-Swiss Renaissance physician, botanist, alchemist and astrologer Paracelsus was famous for which of the following sayings:
“The dose makes the poison.”
What ligand type does NOT change the energy landscape of the receptor?
Neutral Antagonist
What ligand type does NOT change the energy landscape of the receptor?
Neutral Antagonist
Your drug is a weak base with a pKa of 7.0. What compartment will cause the highest level of drug trapping?
Stomach, pH 2.0
Sex Differences in drug distribution can be influenced by:
a) Organ size, blood flow, and total plasma volume
b) Increased resting heart rates and longer QT intervals in female
c) Gastric motility
d) Transporter expression patterns and levels
Which neurotransmitter(s) are released by preganglionic sympathetic neurons?
acetylcholine
Epinephrine is used therapeutically in all of the following situations EXCEPT:
a) Severe allergic reactions (Epipen)
b)Bronchial dilator
c) Cardiac stimulant in emergencies
d) Post-operative ileus and bladder retention
) Post-operative ileus and bladder retention
Side effects of direct and indirect cholinergic medications include all of the following EXCEPT:
a) Runny nose
b) Salivation
c) Decreased urge to use the bathroom
d) Sweating
Decreased urge to use the bathroom
What is the primary vascular effect of treatment with beta 2 adrenergic receptor agonists?
vasodilation resulting in decreased blood pressure
A 60 year old man had a MI (heart attack) in the past. His lipids are abnormal: High total and high LDL cholesterol. Which of these drugs would be prescribed?
Atorvastatin
Which of the following drug classes are useful in the control of hypertension?
a) Calcium channel blockers
b) Angiotensin receptor blockers (ARBs)
c) Thiazide diuretics
beta
RAAS
vasodilators
What is the first substance demonstrated to function as a neurotransmitter
Acetylcholine
Can Acetylcholine derivates be non-selective and selective?
Yes, derivates like methacholine, carbachol, bethanechol are non-selective which can be nicotinic and muscarinic ot selective muscarinic receptor agonist that mimic physiological effects of acetylcholine
What are plant alkaloids
muscarine and pilocarpine are selective muscarininc acetylcholine receptor agonist
What are cholinesterase inhibitors?
neostigmine and physostigmine that block degradation of acetylcholine as the synapse, acting as indirect cholinergic agonists
What are direct and indirect cholinergic agonists used to treat
glaucoma, muscle weakness in myasthenia gravis and to stimulate GI and urinary function
What is muscarinic cholingeric overdose
it is characterized by SLUDGE or PUDDLES response
-miosis, salvation, lacrimation urination, defecation, GI upset, emesis and can be life threatening (coma)
are selective nicotinic agonist limited in therapeutic use?
Yes, use in nicotine addiction
What is nicotine overdose with organophosphates
involved in muscle weakness, fatigue, ad at high doses tachycardia, bronchoconstriction and paralysis