L1: Absorbtion and Distribution of Drugs Flashcards

1
Q

Where should the medicine be introduced to have quick effect?

A

intravenous route.

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2
Q

What is pharmacodynamics?

A

It is what the drug does to the body.

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3
Q

What is pharmacokinetics?

A

It is what the body does to the drug.

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4
Q

What does pharmacokinetics include?

A

Absorbtion
Distribution
Metabolism
Execration

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5
Q

What is elimination?

A

Metabolism + excretion

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6
Q

Why is there some lag in the start of the curve of the time course of drug action (oral)?

A

Due to Absorption but in intravenous, there is no lag.

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7
Q

Where should the drug concentration be kept?

A

In the therapeutic window.

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8
Q

What is absorption?

A

Absorption is defined as the passage of a drug from the site of administration to plasma.

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9
Q

What are the main routes of administration of drugs?

A
  • Sublingual.
  • Oral
  • Rectal.
  • Local.
  • Inhalation.
  • Injections.
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10
Q

Does the sublingual route have any Barriers?

A

No

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11
Q

What are the internal routes of administration?

A
  • Sublingual.
  • Oral
  • Rectal.
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12
Q

What are the external routes of administration of drugs?

A
  • Local.
  • Inhalation.
  • Injections.
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13
Q

What are the factors that affect the rate of Absorption?

A

A. Factors related to the drug:
• Ionization of the drug (pKa)
B. Factors related to the absorbing surface:
• Rate of the circulation at the site of absorption.

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14
Q

What is the ionization constant (pKa)?

A

It is the pH at which the ionized and non-ionized forms of the drug are equal.

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15
Q

Are ionized forms lipid soluble or no?

A

Unionized forms are more lipid-soluble and rapidly absorbed.

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16
Q

Where do acidic drugs become more ionized?

A

In basic media and vice versa

17
Q

Give an example for acidic and basic drugs respectively?

A

Aspirin - amphetamine

18
Q

What is the clinical significance of pKa?

A

-knowing the site of drug absorption on the GIT.

-Treatment of drug toxicity:
• Toxicity with acidic drugs (e.g. aspirin) could be treated by alkalinization of urine, which renders this drug more ionized in urine and less reabsorbable.

• Toxicity with basic drugs (e.g. amphetamine) could be treated by acidification of urine, which renders this drug more ionized in urine and less reabsorbable.

19
Q

What is the action of local anesthetic?

A

They block voltage-dependent Na+ channels within the nerve fibers →↓ nerve conduction.

20
Q

What is the clinical value of pKa in local anesthetics?

A

• All local anesthetics are weak bases. So, the addition of bicarbonate to the anesthetic solution maintains the anesthetic in the non-ionized state and this increases lipid solubility and enhances penetration of the anesthetic into the nerve sheath.

21
Q

What is the bioavailability of drugs?

A

it is the fraction of the drug that becomes available for systemic effect after administration. The bioavailability of drugs given i.v. is 100%.

22
Q

What are the factors that affect drug bioavailability(oral)?

A

Factors affecting oral availability:

  • The same factors of drug absorption.
  • Hepatic first-pass metabolism for oral route
23
Q

What is the definition of volume of distribution?

A

The apparent volume of water into which the drug is distributed in the body after distribution equilibrium

24
Q

How is Vd calculated?

A

The total amount of the drug in the body
Vd = —————————————————————————— = L Plasma concentration of the drug after distribution equilibrium

25
Q

What is the clinical significance of Vd?

A
Knowing Sites of distribution of drugs:
1. Plasma (3 liters)
2. Extracellular (9 liters)
3. Intracellular water (29 liters)
• So, Vd more than 41 liters means drug moves to tissues.

Calculation of the loading dose: LD = Vd target Cp

26
Q

Binding of drugs to plasma proteins

A
  • Most drugs are found in the vascular compartment associated with plasma proteins
  • The pharmacological effect of the drug is related only to its free part.
  • Binding of drugs to plasma proteins prolongs their effects.