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Vets6108* > Pharmocology > Flashcards

Pharmocology Flashcards

1
Q

What is pharmacology?

A

It involves:
1. Pharmacokinetics (how the body affects the drugs)
2. Pharmacodynamics (how the drug affects the body)

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2
Q

What are the 4 processes of pharmacokinetics?

A
  1. Absorption - how will it get in?
  2. Distribution - where will it go?
  3. Metabolism - hoe is it broken down?
  4. Excretion - how does it leave?
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3
Q

What are the factors influencing the absorption in pharmacokinetics?

A
  1. surface area
  2. blood flow
  3. contact time
  4. solubility
  5. polarity
  6. pH
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4
Q

What does absorption mean in pharmacokinetics?

A
  • Route of administration > systemic circulation
  • Liver: first pass effects
  • Bioavailability = net amount available
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5
Q

Which of the following is more effective? Oral medication (tablets) OR IV/IM injection

A

Oral: small intestine > portal venous system (first pass effect liver) > gall bladder/ leave the liver to circulation or target organ

IV/IM injections: bypass GIT (more effective)

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6
Q

What is the 2 important factors of pharmacokinetic distribution?

A
  1. Xenobiotic solubility, ionization and size
    - Fat soluble xenobiotic: lipophilic = hydrophobic
    - Water soluble xenobiotic: hydrophilic = lipophobic
  2. Plasma protein binding
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7
Q

Can the xenobiotic across physiological and cell membrane?

A
  • lipophilic: can pass through cell membranes
  • small and water soluble (<60kd) molecule can pass through a cell gap
  • some molecules need a specific carrier (molecular transporters) to take them into a specific cell
  • Larger water soluble molecules CANNOT pass through cell membrane (unless there’s specific transporter)
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8
Q

Name few physiological barriers.

A
  1. Blood brain barrier
  2. Blood air barrier (lung)
  3. Prostate
  4. Mammary gland
  5. Placenta
  6. Cells lining aqueous and vitreous humor of eye
  7. Blood testes barrier
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9
Q

How does plasma protein affect distribution in pharmacokinetics?

A

Bounded protein is too large to pass through epithelial cells.

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10
Q

What is elimination?

A

Metabolism and excretion

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11
Q

What does metabolism involve?

A

chemical changes of the parent drugs into one or more active or inactive metabolites prior to excretion.

OR

chemical conversion of an endogenous or exogenous substance.

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12
Q

What is excretion?

A
  • A PK process where drug is eliminated from the body unchanged
  • No further chemical reaction, unchanged drug/ metabolite
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13
Q

What is pharmacodynamics (PD)?

A
  • The effect that an endogenous or exogenous substance can have on the body
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14
Q

What is the effect of paracetamol on people?

A
  1. inhibits the enzyme cyclooxygenase in CNS > no dilation and pain
  2. Mechanism of action: minimize the production of prostaglandins which further decrease vasodilate of the blood vessels. When blood vessels in the CNS dilate, they can stimulate pain perception.
  3. Clinical outcome: minimize headache pain in the CNS
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15
Q

What is the 2 different physiological process in xenobiotic elimination?

A
  1. Metabolism
    - Active OR Inactive (no on-going effect)
  2. Elimination
    - Elimination of chemically unchanged drug e.g. penicillin (water soluble)
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16
Q

What is metabolism?

A
  • Is the process that convert lipophilic drugs to more water-soluble metabolites
  • occurs in the liver
  • Metabolism can also occur in enterocytes of the mucosa of small intestine, other organs like lungs, skin
  • may facilitated by microorganisms
17
Q

How many phase are there in metabolism?

A

2 phase.

(i) Phase 1
-Cytochrome P450 enzymes (CYPs) are important phase 1 enzymes
-Phase 1 enzymes catalyst:
a. Oxidation
b. Reduction
c. Hydolysis

(ii) Phase 2
- Is often Phase 1 metabolite with an ionic charge on it.
- Neutralizing parent drugs/ phase 1 metabolite
- Usually a conjugate reaction (a functional group is added on to phase 1 metabolite to make it less active and more water soluble ready for excretion)
- This reactions are either:
a. Sulfation
b. Acetylation
c. Glucuronidation

18
Q

Why is paracetamol toxic to cat?

A

Cat CANNOT undertake paracetamol phase 2 metabolism as they have very small amount of phase 2 glutathione transferase > Phase 1 toxic metabolites build up

19
Q

Which enzyme is needed in the paracetamol metabolism?

A

CYP2E (phase 1)

20
Q

What will Phase 1 toxic metabolite (N-acetyl-p-benzoquinoneimine) lead to? (in cat)

A
  1. Methaemaglobin
  2. Damages RBCs
  3. Damages other cell membrane > oedema
  4. Damages hepatocyte
21
Q
A

Vets6108* (10 decks)

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