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PA MS > Pharmacology and Therapeutics > Flashcards

Pharmacology and Therapeutics Flashcards

1
Q

Factors that determine the route of administration of a drug

A

-Timing (desired speed, desired duration)

-Convenience

-The physical characteristics of the drug

-The need to bypass hepatic metabolism

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2
Q

Factors affecting absorption from the gut ?

A

*Drug Structure
Highly polar/ionised compounds are poorly absorbed
Weak acids/bases can undergo pH partitioning
Peptides can be broken down by digestive enzymes

*Formulation
Capsule/tablet must disintegrate
Modified release formulations

*Gastric emptying
Food generally slows absorption rate due to delayed gastric emptying and stimulation of gastric acid secretion

*First-pass metabolism

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3
Q

What is area under the curve (AUC )?

A

The Area Under the Curve is a measure of
the total amount of drug that enters the body after administration

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4
Q

What is the definition of the term Bioavailability?

A

the fraction of the administered dose that reaches the systemic circulation as intact drug

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5
Q

What is the purpose of determining bioavailability?

A

To determine the dose of drug needs to be administered through different routes of administration.

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6
Q

How to calculate bioavailability ?

A

AUC oral/ AUCiv(100)

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7
Q

What is drug distribution ?

A

The transfer of drug from the general circulation into different organs of the body.

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8
Q

What are the 2 main aspects of drug distribution ?

A

*Plasma protein binding

*Volume of Distribution

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9
Q

What does ADME acronym mean ?

A
  • Absorption from the site of administration
  • Distribution within the body
  • Metabolism
  • Excretion from the body
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10
Q

What are the two ways drug molecules move around the body ?

A
  • bulk flow (i.e. in the bloodstream, lymphatics or cerebrospinal fluid, or during passage through the gastrointestinal tract)
  • diffusion (i.e. molecule by molecule, over short distances).
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11
Q

The rate of diffusion of a substance depends mainly on its?

A

Molecular size. The smaller and lipophilic the drug, the efficient it is to diffuse through lipid membrane

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12
Q

Classical ‘small molecule’ drugs mainly fall within the molecular weight range of ?

A

200–1000 Da

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13
Q

The molecular weight of a monoclonal antibody drug is approximately ?

A

150 kDa

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14
Q

The molecular weight of a RNA drug is approximately

A

16 kDa

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15
Q

What are the main ways by which small molecules cross cell membrane ?

A

*by diffusing directly through the lipid;
* by combination with a solute carrier (SLC) or other membrane transporter (facilitated diffusion)
* by diffusing through aqueous pores formed by special membrane glycoproteins ( aquaporins ) that traverse the lipid by layer.
* small quantities of macromolecules may cross cell barriers by pinocytosis – ‘cell drinking’

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16
Q

permeability coefficient , P determines ?

A

The number of molecules crossing the membrane per unit area in unit time is determined by the permeability coefficient , P , and the concentration difference across the membrane

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17
Q

What are the two physiological factors contributing to the permeability coefficient , P ?

A

1) Solubility in the membrane (which can be expressed as a partition coefficient for the substance distributed between the membrane phase and the aqueous environment)
2) diffusivity , which is a measure of the mobility of molecules within the lipid and is expressed as a diffusion coefficient

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18
Q

The most important determinant of membrane permeability for conventional low-molecular-weight drugs is ?

A

The partition coefficient

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19
Q

Urinary acidification accelerates _____?

A

excretion of weak bases and retards that of weak acids.

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20
Q

Urinary alkalinisation _____?

A

reduces excretion of weak bases and increases excretion of weak acids.

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21
Q

The facilitated diffusion of molecules across lipid barriers are done by?

A

SLC transporters and ATP-binding cassette (ABC) transporters which require ATP.

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22
Q

The facilitated diffusion of drugs are conducted by ?

A

organic cation transporters (OCTs) and organic anion transporters (OATs )

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23
Q

Nephrotoxicity of Cisplatin is caused by ?

A

OCT2 (present in proximal renal tubules) concentrates cisplatin in these cells, resulting in its selective nephrotoxicity.

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24
Q

Nephrotoxicity of Cisplatin can be reduced by ?

A

supplementing Cimetidine which compete for OCT2 with Cisplatin

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25
Q

The OATs are responsible for the renal secretion of?

A

Urate, prostaglandins, several vitamins and p -amino hippurate, and many antibiotics, antiviral, non-steroidal anti-inflammatory and antineoplastic drugs.

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26
Q

What are the main sites where SLCs, including OCTs and OATs, are expressed ?

A
  • the blood–brain barrier
  • the gastrointestinal tract
  • the renal tubule
  • the biliary tract
  • the placenta
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27
Q

The amount of a drug that is bound to protein depends on three factors?

A

*The concentration of free drug
* its affinity for the binding sites
* the concentration of protein

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28
Q

Plasma albumin binds mainly what type of drugs ?

A

acidic drugs (approximately two molecules per albumin molecule)

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29
Q

Factors Affecting Gastrointestinal Absorption of drugs ?

A

– gastrointestinal motility
– gastrointestinal pH
– particle size
– physicochemical interaction with gut contents (e.g. chemical interaction between calcium and tetracycline antibiotics)
– genetic polymorphisms in drug transporters and competition for transporters.

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30
Q

Buccal midazolam is as effective and safe as intravenous or rectal diazepam in terminating___ in children ?

A

early status epilepticus

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31
Q

What is the definition of the apparent volume of distribution?

A

Volume of distribution ( V d ) is defined as the volume of solvent that would contain the total body content of the drug ( Q ) at a concentration equal to the measured plasma concentration ( C p ), V d = Q / C p .

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32
Q

The plasma volume is equal to ?

A

0.05L/kg BW

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33
Q

The total ECF volume is ?

A

0.2L/kg BW

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34
Q

The total body water volume is ?

A

0.55L/kg BW

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35
Q

The volume of major compartments of body are

A

– plasma (5% of body weight)
– interstitial fluid (16%)
– intracellular fluid (35%)
– transcellular fluid (2%)
– fat (20%)

36
Q

What are the effects of drug competition ?

A
  • Harm from the transient increase in concentration of free drug before the new steady state is reached.
  • If dose is being adjusted according to measurements of total plasma concentration, it must be appreciated that the target therapeutic concentration range will be altered by co-administration of a displacing drug.
  • When the displacing drug additionally reduces elimination of the first, so that the free concentration is increased not only acutely but also chronically at the new steady state, severe toxicity may ensue.
37
Q

Basic drugs bind to what protein?

A

Alpha-01 acid glycoprotein

38
Q

Factors affecting drug- protein binding?

A
  • Hypoalbuminemia
  • Uraemia
    *Age
  • Competition for binding sites
39
Q

If a drug’s volume of distribution is between 1 and 500 L / kg, the drug is mainly distributed in ?

A

Tissue and very little in plasma

40
Q

If a drug volume of distribution is between 0.2 and 0.5 L / kg, the drug is distributed ?

A

Similar concentration in plasma and tissue.

41
Q

If a drug volume of distribution is between 0.05 to 0.2 L / kg, the drug is mainly distributed in ?

A

Localized mainly in plasma little in tissue.

42
Q

What are the two phases of drug elimination metabolism ?

A

*Phase I Catabolism (oxidation, reduction, hydrolysis)
*Phase II Anabolism (conjugation)

43
Q

Aspirin toxicity is treated by ?

A

urine alkalisation.

44
Q

effect of Grapefruit juice and St. John’s wort on CYP3A4 activity

A

Grapefruit juice reduces and St. John’s wort increases CYP3A4 activity

45
Q

Major routes of drug elimination

A

*Renal
*Biliary/Gastrointestinal
*Pulmonary

46
Q

A patient has taken a paracetamol overdose, what can be done?

A

administer IV Glutathione Or N-acetyl cysteine to convert NAPQI to nontoxic form for renal excretion.

47
Q

Most drugs are eliminated by ?

A

First oder elimination kinetics.

48
Q

The amount of drug eliminated is directly proportional to the ____?

A

plasma concentration.

49
Q

The fraction of drug eliminated is ____

A

constant ( 50% eliminated per unit time of the plasma concentration)

50
Q

Plasma half life is defined as ?

A

the time for plasma concentration to fall by 50%

51
Q

Plasma half life is independent of dose and it is determined by ?

A

*Activity of metabolising enzymes and excretion mechanisms – clearance
*Distribution of drug between blood and tissues

52
Q

The plasma half life of drugs with high Vd is ?

A

longer due to distribution in tissue compartments.

53
Q

General rule of plasma half life ?

A

4 half lives after the cessation of drug the plasma concentration would have fallen by approximately 94%

54
Q

steady state of drug infusion is defined as ?

A

the time point in which the quantity of drug administered match the quantity of drug eliminated by the excretory systems. The in-out equilibrium.

55
Q

General rule of steady state ?

A

4 half-lives after starting constant iv infusion, drug plasma concentration will have reached steady state

56
Q

What is the strategy for achieving steady state of IV infused drug quicker ?

A

combine IV infusion with bolus infusion.

57
Q

When and how to estimate the drug clearance rate ?

A

The drug clearance rate can by estimated at the steady state of drug administration by dividing the infusion rate by plasma concentration ( infusion rate/ plasma concentration)

58
Q

What is the definition of therapeutic index ?

A

The therapeutic index is a ratio of the dose required to produce a specified toxic effect in 50% of the population (TD50) divided by the dose required to produce a specified desired response in 50% of the population (ED50).

59
Q

How to calculate therapeutic index of a drug ?

A

TI = TD50/ ED50

60
Q

What are the four families of receptors based on their structure?

A
  • Ligand gated iron channels ( acts in milliseconds)
  • G protein coupled receptors ( acts in seconds)
  • Tyrosine kinase receptors( acts in minutes)
  • Intracellular receptors ( acts in hours to days)
61
Q

What are G proteins ?

A

These are the enzymes that convert GTP to GDP. Therefore, they are called GTPases.

62
Q

How are G- protein coupled receptors activated?

A

The G protein coupled receptors are activated by Gunine nucleotide exchange factor which replaces GDP with GTP.

63
Q

How does G protein coupled receptors get inactivated?

A

When the GTPases convert GTP to GDP

64
Q

Where does GTpase activity take place?

A

G alpha subunit.

65
Q

What are kinases ?

A

Kinases are enzymes that phosphorylate proteins.

66
Q

What are phosphates ?

A

Phosphates are enzymes that dephosphorylate proteins.

67
Q

What is the most common GAP protein responsible for activating GTPases to convert GTP to GDP and inactivating the G-protein ?

A

Regulator of G protein signaling RGS.

68
Q

What are the two effector enzymes used in GPCR signalling?

A

Adenylate cyclase
Phospholipase

69
Q

What is the role of Adenylate cyclase?

A

It is an enzyme responsible for converting ATP into cyclic aMP

70
Q

What is a ligand ?

A

A ligand is a chemical which specifically binds to a receptor.

71
Q

What is an agonist drug ?

A

An agonist drug is a ligand which binds to a receptor and causes a biological response.

72
Q

What is an antagonist drug ?

A

An antagonist binds to a receptor and has no effect but prevents other ligands from binding.

73
Q

Characteristics of a receptor?

A
  • structural and steric specificity.
    *expressed in select tissues
    *saturable and finite
    *high affinity for its endogenous ligand at physiological concentrations .
  • The edogenous ligand binding initiates biological action.
74
Q

What is the law of mass action ?

A

the law of mass action is the proposition that the rate of the chemical reaction is directly proportional to the product of the concentrations of the reactants

75
Q

What is the definition of potency ?

A

Potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity.

76
Q

what are partial agonists ?

A

These are drugs that never produce a maximal response.

77
Q

What is competitive antagonism

A

A competitive antagonist binds to the same site as the agonist and the two compete with each other in which the binding is reversible and surmountable with excess agonist. The maximum effect of agonist is not affected, however, the dose required to elicit maximum effect is increased.

78
Q

What is non competitive antagonism

A

Antagonist binds to a different site to agonist and the Binding is reversible.
Binding cannot be overcome by increasing agonist concentration (insurmountable).

79
Q

What is IC50?

A

The dose that inhibits the response of agonist by 50% =IC50.

80
Q

Adenylate cyclase activity for coverting ATP to cAMP is inhibited by

A

Phosphodyestrase which break down cAMP to AMP

81
Q

Atrial Naturetic Peptide (ANP) is
associated with

A

guanylate cyclase activity

82
Q

What are adaptor proteins ( enzyme linked receptors ) ?

A

Adapters do not
participate in signalling
they just facilitate the
interaction between
signalling proteins.
Grb2 is a typical
adapter

83
Q

What are the tree type of iron channels ?

A

Voltage gated, ligand gated and stress mediated.

84
Q

What are heat shock proteins ?

A

Heat shock proteins are a family of
proteins that are dramatically
upregulated after cells are exposed to
heat and act to chaperone other proteins.
They act to help proteins fold, to re-fold
mis-folded proteins and to guide proteins
to the correct location.

85
Q
A
86
Q

What is an inverse agonist?

A

An inverse agonist is a drug that binds to the receptor just as the antagonist. Unlike antagonist it down regulates the agonist mediated cell signalling

PA MS (44 decks)

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