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KHI > PBL 7: Gavin Lee -Drug Overdose > Flashcards

PBL 7: Gavin Lee -Drug Overdose Flashcards

1
Q

Enzymes

A

Drugs that bind to the active site and cause a conformational change

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2
Q

Steroid Drugs

A

Lipid Soluble and pass easily through the membrane to effect DNA

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3
Q

Ligand-Gated Ion Channels

Outline

Time Scale

Examples

A

Outline: Ligand binds to receptor on cell membrane causing hyperpolarisation or depolarisation which then exert a cellular effect.

Time Scale: milliseconds

Examples: Nicotinic Receptors, ACh Receptors

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4
Q

G-Protein Coupled Receptors

Outline

Timescale

Examples

A

Outline: molecule binds to receptor on extracellular side of transmembrane protein, causing dissociation between subunits that activated second-messenger cascade. May cause, Ca2+ release, Protein phosphorylation or other cellualr effects.

Time Scale: Seconds

Examples: Muscarinic Ach receptor

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5
Q

Kinase-linked receptors

Outline

Timescale

Examples

A

Outline: molecule binds to receptor causing protein phosphorylation that leads to gene transcription, protein synthesis thus exerting cellular effects.

Timescale: Hours

Example: Cytokine receptors

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6
Q

Nuclear Receptors

Outline

Timescale

Examples

A

Outline: Receptors within the nucleus which promote gene transcription. This leads to protein synthesis and exerted cellular effects.

Timescale: Hours

Example: Oestrogen Receptor

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7
Q

What receptors are required for Peptide drugs and Hormones?

A

Surface protein remember on the cell membrane

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8
Q

What are competitive antagonists?

A

Molecules that compete with the agonist for the binding site on the receptor

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9
Q

What effect does the competitive antagonist have on VMAX (efficacy)

A

Does not change the Vmax of the drug

Increasing [agonist] can overcome effects of the antagonist

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10
Q

How strong is competitive antagonist receptor binding?

A

Weak

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11
Q

How do competitive antagonists effect the dose/response curve?

A

Shift to the RIGHT

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12
Q

What is an example of a competitive antagonist?

A

Naloxone

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13
Q

How do Irreversible Antagonists bind to receptors and what is the strength of the bond

A

Covalent bonding (very strong)

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14
Q

How do Irreversible Antagonists effect the dose/response curve?

A

Reduces efficacy and potency (curse shift DOWN and RIGHT)

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15
Q

What is an example of an Irreversible Antagonist

A

Aspirin

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16
Q

What is an example of a Partial Agonist

A

Methadone on opiate receptors.

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17
Q

Define ED50

A

The potency of therapeutic effect

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18
Q

Define TD50

A

The potency of toxic effect

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19
Q

Define LD50

A

Potency of lethal effect

20
Q

What is the therapeutic index?

A

Therapeutic Index = TD50 / ED50

The ratio between the toxic and the therapeutic dose for half the population

A high TI means you can give more drug without being too concerned about toxicity.

21
Q

Recognize that drugs may behave as reversible or irreversible competitive antagonists of receptors for endogenous ligans

A

Recognize

22
Q

Define Bioavailability

A

The fraction of dose which reaches the systemic circulation as an intact drug

23
Q

How do we calculate bioavailability?

A

F = Fg x FH

Fg = absorbed in GI tract

FH = fraction escaping liver (1-EH)

EH = fraction metabolized by liver (CLH/QH)

24
Q

Hepatic First Pass Clearance

A

The extrent to which a drug is removed by the liver on first passage in the portal blood through the liver to the systemic circulation

25
Q

Intravenous Bioavailability

A

IV has a bioavailability of 1 as the drug enters the systeming circulation immediately without being subject to hepatic first pass clearance

26
Q

Factors affecting Oral Administration bioavailability

A
  1. Absorption into GI
  2. Size, shape and charge alteration
  3. Subject to hepatic first pass clearance
  4. Renal Clearance
27
Q

VD

A

VD = Total drug in the body / blood plasma concentration

The concentration of drug in the blood compared to total amount of drug in the body.

28
Q

Clearance (CL)

A

The rate at which a drug is irreversibly metabolize/removed from the body (volume per unit time).

CLsytemic = CLrenal + CLhepatic

29
Q

Half-Life

A

The time taken for the concentration of a drug to fall by half of its current concentration

  1. Duration of action after a single dose
  2. Time required to reach staeady state with chronic dosing
  3. Dosing frequency required to maintain steady state concentrations in plasma
30
Q

Elimination half-life

A

t1/2 = 0.693 x V

_____________

CL

31
Q

Steady State

A

A balance of drug input with drug clearance, achieved after 3-5 half-lives

32
Q

QH

A

Hepatic Blood Flow

Assume (healthy) QH = 90L/h

33
Q

EH

A

Hepatic extraction ratio

Concentration of blood entering - Concentration of blood leaving / concentration of blood entering

EH = CLH (Hepatic Clearance) / QH

34
Q

High Hepatic Drug Clearance

A

>0.67

Major determinant is Blood Flow

35
Q

Low Hepatic Drug Clearance

A

<0.2

  1. Intrinsic clearance (enzyme activity)
  2. Fraction of unbound drug in the blood - FU
36
Q

Drug Elimination for single dose oral administration

A
  1. Dose is given
  2. The administered dose x Fg = dose entering portal blood
  3. Hepatic first pass dose in portal blood x (1-EH) = dose entering arterial blood
  4. Each half-life circulating dose decreases by half: (circulating dose = CLS)
37
Q

Drug Elimination time course for single dose IV administration

A
  1. Dose administered
  2. Dose administered enters arterial circulation
  3. Each half-0life circulating dose decreases by half (circulating dose - CLS)
38
Q

Which receptors do Opiods bind to that primarily effect respiration?

A
  1. μ2 receptors
39
Q

What affect does μ2 receptor binding by opiates have on the Central Respiratory Center of the Medulla?

A
  1. Decreases sensitivity to PCO2
    resulting in reduced firing from the repiratory centre for a given PCO2

LOWERS pO2 and RAISES pCO2 which gives HYPOXIA

  1. Lowers firing of respiratory neurons and Recruitment of respiratory muscles

Therefore lowers VENTILATION

LOWERS pO2 and RAISES pCO2 which gives HYPOXIA

40
Q

What affect does μ2 receptor binding have on the Pre-Botzinger Complex Activity?

A

Decreases Activity leading to

  1. Decreased firing of respiratory neurons
  2. Decreased recruitment of respiratory muscles

Therefore reduced VENTILATION

LOWERS pO2 and RAISES pCO2 which gives HYPOXIA

41
Q

What does Hypoxia stimulate?

A

The Hypoxia ventilatory response

42
Q

How does opiod receptor binding affect peripheral sensitivity to PO2

A

Lowers

43
Q

Why can’t the Hypoxia ventilatory response compensate for hypoxia?

A

Reduced peripheral sensitivity to PO2 inhibits the response

Unable to normalise PO2 and PCO2 due to reduced sensitivity of central and peripheral chemoreceptors.

44
Q

What are the 3 major effects of Opiod μ2 receptor binding on control of respiration?

A
  1. Decreased sensitvity to PCO2 in the Central Respiratory Center
  2. Decreased activity of the Pre-Botzinger Complex
  3. Decreased Peripheral sensitivity to PO2
45
Q
A

KHI (8 decks)

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