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Pharmacology > Basic Principles Exam 1 > Flashcards

Basic Principles Exam 1 Flashcards

1
Q

Define a drug.

A

Drugs are chemical substances that are used for the diagnosis, prevention or treatment of disease, and for the prevention of pregnancy.

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2
Q
  • Define the term “pharmacokinetics.”

- What are the 4 major steps of drug movement in body?

A

● Pharmacokinetics is the study of how a drug enters the body, circulates within the body, is changed by the body, and leaves the body.

●	Pharmacokinetics encompasses 4 major steps of drug movement in the body:
○	Absorption
○	Distribution
○	Metabolism
○	Excretion
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3
Q

Define the term “pharmacodynamics.”

A

○ Study of the biochemical & physiologic actions of drugs, and their MECHANISMS of drug ACTION at the cell level and sub-cell level

○ What the drug DOES to the body

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4
Q

Define the characteristics of drug molecules.

A

-Characteristics of the drug molecules influences whether a drug can cross a lipid membrane

○ Lipid solubility= the more lipid soluble, the easier that the drug will cross

○ Degree of ionization (charge) = charged molecules CANNOT cross (must use pores/channels)

○ Molecular size= small size crosses easily

○ Shape of the drug molecule= molecules can “contort” to fit through the membrane

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5
Q

Describe the ionization of weak acid drugs and weak base drugs relative to pka.

A

● pKa= acid dissociation constant

■ Aspirin example to show dissociation:
Aspirin is a weak acid; pKa for aspirin = 4.4
● In acid environment of stomach, aspirin dissociates to 1000 uncharged molecules (lipid soluble) to 1 charged molecule (polar, water soluble) = acid gets absorbed across wall of stomach (membrane) into plasma because most of drug is in lipid soluble form

● However, once in plasma (pH = 7.4), ratio of dissociated aspirin molecules changes: 1000 charged (polar, water soluble) to 1 uncharged (lipid soluble) = aspirin cannot pass back thru blood vessel wall membrane into stomach

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6
Q

Describe the ionization of weak acid drugs and weak base drugs relative to lipids/water solubility

A

● lipid and water solubility
○ lipid soluble= non-ionized (no charge)
○ water soluble= ionized (polar)

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7
Q

Why are many compounds used for medication are weak acids or bases?

A

So a knowledge of the pKa and log p values is essential for an understanding of how compound enters (or does not enter) the blood stream. Non ionized (uncharged) forms can diffuse across membranes

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8
Q

Describe the ionization of weak acid drugs and weak base drugs relative to acids and bases

A

● Acid-base form:

1) Weak ACID in an ACIDIC environment= Lipid soluble
2) Weak ACID in a BASIC environment= Water soluble (dissociates)
3) Weak BASE in ACIDIC environment= Water soluble (dissociates)
4) Weak BASE in a BASIC environment= Lipid soluble

● low pH and neutral pH

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9
Q

Henderson-Hasselbach Equation?

A

○ ***Main pt of Q as stated by professor: The focus of this key principle is that the pH of the environment will determine which form of the drug predominates = and as you so nicely stated, determines whether or not the drug can move to/from a compartment to access it’s target tissue. Weak acids do better in an acidic environment, because there is less dissociation = remain lipid soluble, so they are able to cross membranes, etc.

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10
Q

Differentiate between enteral and parenteral routes of administration.

A

● Enteral = drugs given by this route are placed directly into the GI tract
○ oral
○ rectal

● Parenteral = parenteral administration bypasses the GI tract and includes various injection routes, inhalation and topical drug administration

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11
Q

Describe the Inhalation route by which drugs are administered in the body.

A

○ no needles
○ Rapid drug access to the circulation via the lungs, local and systemic

***PARENTERAL

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12
Q

Describe the Intravenous route by which drugs are administered in the body.

A

○ Most rapid response
○ Immediate onset of action
○ Predictable response

***PARENTERAL

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13
Q

Describe the Intramuscular route by which drugs are administered in the body.

A

○ Drugs that are irritating to the GI tract can be better tolerated this way
○ Sustained effect of the drug (absorbed more slowly)

***PARENTERAL

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14
Q

Describe the Topical route by which drugs are administered in the body

A

○ Applied to surfaces of the body
○ Local or systemic effects depending on concentration
■ Local - does not penetrate intact skin
■ Systemic - topical corticosteroids, some topically applied local anesthetics

***PARENTERAL

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15
Q

Describe the Subcutaneous route by which drugs are administered in the body.

A

○ Injection of solution beneath layers of skin into the subdermal layers for systemic absorption
○ PPD Test for Tuberculosis
○ Insulin injections for diabetics

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16
Q

Describe the Sublingual route by which drugs are administered in the body.

A

○ Rapidly absorbed
○ Placed under tongue in the floor of mouth
○ Nitroglycerin for angina
(vasodilator for chest pain)

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17
Q

Describe the Transdermal route by which drugs are administered in the body.

A

○ Patches provide slow continuous release of a medication through a semi-permeable membrane
○ Drugs are lipid soluble to penetrate lipid bilayer of skin
○ Drug delivered in path is more concentrated than in another delivery vehicle

-Hormone patches, smoking cessation patches

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18
Q

Describe the Intrathecal route by which drugs are administered in the body.

A

○ Injection of solutions into the spinal subarachnoid space seen in epidurals

-Treatment of spinal meningitis

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19
Q

Describe the Intraperitoneal route by which drugs are administered in the body.

A

○ Places fluid into the peritoneal cavity for exchange of substances
○ Form of dialysis
-Be cautious of the potential for infection

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20
Q

Describe the 2 ENTERAL routes drugs enter body

A

● Oral :
○ Cheapest, easiest, most convenient
○ Tablets, Capsules, Liquids, Lozenges

● Rectal :
○ Used if patient is vomiting or unconscious (systemic effects)
○ Poorly or irregularly absorbed from rectum
○ Used for babies & toddlers

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21
Q

Define, compare and contrast the following drug dose forms: solution, syrup, suspension, emulsion, tincture, and elixir.

A

○ Solution, syrup, emulsion, tincture, elixir- Oral route, liquids absorbed more quickly than tablets

○ Rate of onset:

  • IV: control rate, continuous
  • IM- deliver large quantity
  • Patch: continuous delivery, slow release
  • Sublingual: rapid delivery
  • Subcutaneous- slow onset
  • Inhalation: rapid onset
  • Ointments/sprays: dose control
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22
Q

Describe the mechanisms by which drugs penetrate biological membranes.

A
  • Factors affecting membrane crossing:

● Lipid solubility= the more lipid soluble, the easier the drug will cross
● Degree of ionization (charge)= charged molecule cannot cross
● Molecular size= small size crosses easily
● Shape of the drug molecule= molecules can “contort” to fit through the membrane

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23
Q
  • How do molecules cross membranes?
A

● Diffusion= lipid-soluble drugs move across the membrane passively, from the compartment of highest drug concentration to the compartment of lowest drug concentration

● Filtration= small molecules that are water-soluble pass through membrane pores by bulk flow of water

● Specialized transport= large, ionized water-soluble drugs require a more complex mechanism than simple diffusion
○ Facilitated diffusion= drug forms a complex with a component of cell membrane on one side; carried thru membrane; drug released inside

■ mechanism for movement of glucose
○ Active transport= movement of drug molecules across biological membranes against both a concentration & electrochemical gradient
■ requires ATP

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24
Q
  • What influences the rate of drug movement across membranes?
  • How do we get drugs into the body?
A

1) The physiochemical factors that were just discussed
● The drug’s solubility= drugs dissolved in solutions are more rapidly absorbed than insoluble drugs
● The route of administration

2) The closer the site of administration is to a blood vessel, the faster a drug can be absorbed

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25
Q

Discuss the differences in drug absorption between oral, injected and intravenous administration.

A

● Intravenous - Most rapid response- immediate, directly into blood.

● Injected - Slow sustained release- occurs due to high blood flow through skeletal muscles.

● Oral - usually enteral, cheapest and easiest, and can be taken as tablets, liquids, lozenges.

26
Q

Describe the “first pass effect” of drug metabolism after oral absorption.

A

Summary: 1st pass effect is when drugs taken orally go thru portal circulation into the liver. Drugs given parenterally DO NOT go thru 1st pass effect. P450 enzymes in liver & intestines

● Drugs that are administered orally pass from the stomach to the intestine to the portal veins; from portal veins, drugs enter the liver
● P450 enzymes are located in the intestinal epithelium and the liver
● Metabolize drugs to inactive forms before they have the chance to enter the systemic circulation
● “first pass effect” or first pass metabolism
● Drugs given parenterally bypass this effect (put directly into bloodstream

27
Q

Define the term “bioavailability.”

A

● Fraction of the administered drug that becomes available in the plasma
○ ONLY IV administration gives 100% bioavailability
○ Frequently influenced by the “vehicle” of the drug
● This concept became important w/ use of generic drugs: drug molecule same; vehicle differs
● FDA mandates that generics MUST have 90% of the availability of the parent compound

28
Q

Describe the mechanism of drug transport in the plasma to tissue sites.

A

Definition of drug distribution = drug movement from the site of absorption to the site of action

● Drugs occur in 2 forms in blood:
○ 1) Bound to plasma proteins
■ no effect
○ 2) “Free” or unbound drug
■ Only the free form can pass across cell membranes and exert desired effect
● drugs leave the plasma and enter into interstitial fluids
● “ratio” of bound:unbound drug remains the same in the blood
● Some drugs may be poorly distributed to certain areas

○ ***Only FREE FORM can pass across cell membranes (on exam) & leave blood to produce effect. Then Bound drug becomes UnBound (ACTIVE). (Ratio Stays Constant Bound/UnBound)

29
Q
  1. Identify and describe potential barriers to drug distribution in the body.
A

●Blood brain barrier= drugs that can cross this barrier are lipid-soluble, very small molecular weight/size, and exert effects on the central nervous system
●*Placenta= most drugs cross easily; lipid-soluble drugs cross most easily
Distribution = passage of drugs into various body fluid compartments:

•	Plasma
•	Interstitial fluids
•	Intracellular fluids
o	Some drugs may be poorly distributed to certain areas 
•	Charge of drug molecule
•	Size of drug molecule
•	Permeability of membrane barrier
30
Q

Describe the concept of drug redistribution for termination of drug activity.

A

● Movement of the drug from the site of action to nonspecific sites of action
● Duration of action can be affected by redistribution from one organ to another
● If redistribution occurs between specific sites and nonspecific sites, the drug’s action will be terminated

● Example: An “induction” agent is administered to induce sleep before anesthesia for surgery. After a few minutes, action is terminated, because drug has been redistributed from CNS via the plasma to skeletal muscle (action terminated) to finally fat depots in the body (no action).

31
Q

Define drug biotransformation.

A

● AKA drug metabolism
● Body’s way of changing the drug so that it’s more easily excreted by KIDNEYS
● Converts lipid soluble drugs to water soluble metabolites

● Metabolites are LESS likely to bind to plasma proteins or stored in fat = EASIER to excrete
● Most commonly occurs in the LIVER (also in kidneys, lungs, nerves, plasma, intestines)
○ Liver enzymes (cytochrome P450 system)
○ Microsomes are organelles in hepatocytes *where most drug transformation takes place
○ Liver function DECLINES w/ age
○ PATHOLOGY alters drug metabolism - Often requires a dose modification
■ Cirrhosis
■ Hepatitis
■ Damage to liver from drugs

32
Q

What are the Mechanisms for Biotransformation?

A

○ Active to inactive = MOST common
■ Inactive drug is formed from active parent drug

○ Inactive to active = “prodrugs”
■ Inactive parent drug is converted to an active drug after metabolism

○ Active to active
■ Active parent drug is converted to a second active drug (metabolite is active)

33
Q

Discuss the phases of drug biotransformation.

A

Net effect = makes drug water soluble
● Phase I = drug molecule is modified thru OXIDATION, REDUCTION or HYDROLYSIS

○ Expose or alter a functional group (eg. hydrolysis, demethylation, ect.)
○ Usually INACTIVATES drug molecule
○ Exposes a site that can be altered by Phase II reaction

● Phase II = drug molecule is modified by CONJUGATION to a large polar endogenous molecule
○ ADDS large “bulky” molecule to functional group exposed in Phase I
■ Glucuronide, sulfate, glutathione, etc
○ Phase I reactions can undergo additional Phase II reactions
○ Phase II metabolites are pharmacologically INACTIVE
○ INCREASES water solubility to prepare for excretion by the kidney

34
Q

Discuss the characteristics of the microsomal oxidation enzyme system.

A

● Endoplasmic like intracellular organelles which possess the enzymes required for biotransformation of most drugs in liver hepatocytes.

35
Q

Discuss how drugs are eliminated from the body.

Phase I & II

A

● Movement of a drug or its metabolites out of the body

● (Metabolism (biotransformation) converts lipid soluble drugs into water soluble metabolites which are readily excreted. The altered drug is less likely to bind a plasma protein and be retained in fat stores.

● -Phase I: Expose or alter a functional group (hydrolysis, methylation, etc) which usually inactivates the molecule leading to phase II reactions.

● -Phase II: Addition of large functional groups (glucuronic acid, sulfate, glutathione) which always inactivates the molecule. The molecule becomes highly water soluble and ready for filtration by the kidneys and excretion.

36
Q
  • What is the Principal organ of drug excretion_____?
  • All drugs in the blood are filtered by what?
  • What does Clearance rate =?
  • What are some Clinical considerations?
A

-The kidney

●ALL drugs in blood are filtered by the kidneys

● Clearance rates= known value describing excretion rates

● Clinical considerations:

1) Kidney function declines w/ age
2) Altered kidney function from disease
3) Salivary drug concentration mimics plasma concentration

37
Q

List the routes of drug excretion from the body.

A 
●	Kidney→ urine
●	Bile→ GI tract→ feces
●	Sweat
●	Saliva= salivary concentration mimics plasma concentration
●	Lungs= gases; alcohol (Breathalyzer)
●	Breast milk
38
Q

Define the biological “half-life” of a drug.

A

● Amount of time needed for the plasma concentration of a drug to fall to one half of its blood level per unit of time
● Most drugs are cleared by 4-5 half lives
● It takes ~ 4 to 5 half-lives for a drug to build up to a steady state level

39
Q

Compare the concepts of first order elimination with zero order elimination.

A

● A given amount of drug is eliminated per unit time

● Alcohol is eliminated at a rate of 1 gram per hour (no half-life)= rate is CONSTANT

40
Q

Discuss the concept of first order drug elimination.

A

● Amount of drug eliminated is dependent upon the amount of drug in the plasma at any given time

● Constant fraction of the drug is eliminated per unit time= clearance rate

● Distribution half-life= rapid decline in plasma drug concentration as 50% of drug distributed throughout the body

● Elimination half-life= required to excrete 50% of drug from the system

41
Q

Define the plasma steady state concentration.

A

● Following administration of multiple therapeutic dosages of a drug at regular time intervals, a plateau level of drug accumulates

● Plateau represents a rate of drug administration that is equal to the rate of drug elimination

42
Q

Discuss how the steady state concentration is achieved.

A

● At a regular dosing frequency, the drug does not accumulate and a steady state or equilibrium is eventually reached

43
Q

Describe how drugs interact with receptors.

A

● Drugs attach to or interact with receptor sites by covalent, ionic, hydrogen, hydrophobic, or Van der Waals binding to produce a definable pharmacological response

● Hydrogen binding & ionic binding are the MOST common

● Interactions require little energy, and may be easily broken

● Affinity of a drug for a particular receptor and type of binding is intimately related to drug’s chemical structure

● Drug binding occurs at multiple sites (amino acid residues) on protein structure

● Binding to one or more amino acid residues causes a conformational change in
protein molecule

● This results in a modification of the tertiary structure to bring other amino acid residues closer to drug = called an “induced fit”

● Drugs also bind to receptor proteins within the cell structure
○ Receptor protein does not exist as an isolated substance external to the cell
○ Receptor protein may be a structural or enzymatic component of cell membrane = part of cell membrane

44
Q

Describe the concept of “induced fit” for a drug molecule with a receptor.

A

● Drug causes conformational change in the protein

● Brings other amino acid residues in close association with the drug

● Sometimes known as the “lock and key” mechanism of drug binding

45
Q

Describe the general mechanisms of drug-receptor interaction.

A

● Many receptors are components of cell membrane structure

● These proteins facilitate communication between 2 sides of the membrane

● These proteins exist naturally as receptors for hormones, neurotransmitters & growth factors
● These proteins recognize selected molecules at external surface and transmit information to the inside of the cell

46
Q

Describe the configuration of membrane spanning protein receptors.

A

● Proteins which act as drug receptors span cell membrane (extend from the outside of the cell, cross through the membrane and inside the cell)

● These proteins can communicate w/ BOTH sides of the cell membrane

● By recognizing molecules at the external membrane surface, they can transmit information to the inside of the cell

47
Q

Define the term “ligand.”

A

● Molecules that bind to receptor protein or receptor glycoprotein

● May be hormones, neurotransmitters, growth factors or drug molecules

48
Q

Define the term “cell signaling.”

A

● When a ligand binds to a specific area of receptor protein on outer surface of the cell, or within cell membrane, a conformational change occurs in receptor-protein molecule which is transmitted to inner surface of cell membrane

● This change is a signal that initiates cell’s response to the binding of the ligand

49
Q

Describe various cell signaling substances in the body.

A

● Hormones like INSULIN are LIGANDS which induce cell signals

● Neurotransmitters such as norepinephrine are cell signaling ligands

● Growth factors such as growth hormone are cell signaling ligands

● Drugs

50
Q

Describe examples of cellular responses that occur following cell signaling.

A

● Ion channel opening or closing
● Formation of intracellular second messenger
● Alterations in gene expression of the cell
● Initiation or alterations in cell growth and differentiation

51
Q

Discuss drug molecule interaction with receptors that control ion channels.

A

● Ligand binding occurs directly to receptor at channel site

● Receptors are located on ligand-gated channels & voltage-gated channels

● Binding causes channel to OPEN, allowing for the INFLUX of ions
● Key Point: Binding INCREASES cell membrane permeability to sodium & potassium = determines depolarization or hyper polarization of nerve = affects nerve firing

52
Q

Discuss drug molecule interaction w/ receptors that regulate the generation of intracellular second messengers.

A

● Receptors that regulate the generation of intracellular second messengers (G proteins)
○ Receptors are located cell membrane
○ Transmit information from outside to inside the cell

○ Ligand binding causes a series of events which generate a second messenger (ligand is considered first messenger)

○ Second messengers pass message from inside of cell to effector organ (target site of action)

53
Q

Describe the intracellular G-protein complex and the activated G-protein complex.

A

● Many of the receptors which generate second messengers are coupled to substances known as G-proteins

● G-proteins are located at internal portion of cell membrane & regulate the generation of intracellular second messengers

● Some hormone receptors & neurotransmitter receptors (e.g. in the autonomic nervous system) depend on G proteins to mediate actions on cells

54
Q

List the 3 results of effector activation.

A

● Activated effector can be:

○ 1) adenylyl cyclase - Cell’s response is the generation of cyclic AMP (cAMP)
○ 2) phospholipase C - Cell’s response is phosphorylation of proteins
○ 3) a membrane channel - Cell’s response is a change in ionic conductance

55
Q

Define drug potency.

A

● Amount of drug necessary to produce the effect (think dose of the drug)

○ Related to affinity of drug to its receptor

56
Q

Define drug efficacy.

A

● Efficacy is the degree of maximum intensity of effect (think EFFECT of the drug)

○ MAXIMUM response produced by a drug

○ Related to receptor occupancy by drug molecules

○ Additional doses produce NO additional benefit: “ceiling dose” occurs when ALL receptors are occupied (intrinsic drug activity once a drug-receptor complex is formed)

57
Q

Differentiate between drug potency and drug efficacy with regard to the relationship between drug dose and effect.

A

● Potency is DOSE Exp: Demerol is more potent than aspirin (it takes LESS Demerol to produce its effect

● Efficacy is EFFECT. Exp: Demerol is MORE effective than aspirin in relieving pain (it has a GREATER maximum effect)

58
Q

Differentiate between an agonist and an antagonist.

A

● Both agonist & antagonist compete for same receptor site

● Agonist
○ A drug that is able to bind a receptor & produce an effect
○ Produce SIMILAR EFFECTS as endogenous chemicals
○ Neurotransmitters, hormones, etc (think ligands)

● Antagonist - ALWAYS binds first!!
○ Drug that binds to same receptor as an agonist, but is unable to activate receptor
○ Produces NO EFFECT
○ Antagonist drug oppose actions of an agonist by reducing or inhibiting effect
○ “blocker” drugs eg. beta blockers, calcium channel blockers

59
Q

Differentiate between competitive versus non-competitive antagonists.

A

● Competitive antagonist competes with agonist for same receptor site, & blocks the receptor
○ Binding of antagonist is reversible
○ Administering additional agonist will displace antagonist from receptor, allowing agonist to produce effect

● Non-competitive:
○ Noncompetitive antagonist binds irreversibly= cannot be displaced
○ Can bind to either same receptor site as agonist or a different site= both actions inhibit effect of agonist
○ “Think poisons”

60
Q

Compare and contrast pharmacologic antagonism w/ physiologic antagonism.

A

● Physiologic Antagonist:
○ ACTIVATES pathways that oppose action of agonist
○ Agonist & Antagonist act independently on 2 different receptors
○ LESS desirable in medicine than receptor-specific antagonists

●	Pharmacologic antagonism:
○	Both agonist & antagonist compete for SAME receptor site
○	Antagonist binds FIRST
○	PREVENTS agonist from producing effect
○	Either competitive or non-competitive
61
Q

Describe the “therapeutic window” for drug effects.

A

● Range of the doses (concentrations) of a drug that elicits a therapeutic response, without unacceptable side effects (toxicity) in a population of people

● Blood plasma levels of a drug w/ a small therapeutic window MUST be monitored closely to maintain effective dosing without exceeding level that could produce toxicity

Pharmacology (13 decks)

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