L1: Absorbtion and Distribution of Drugs Flashcards
(26 cards)
Where should the medicine be introduced to have quick effect?
intravenous route.
What is pharmacodynamics?
It is what the drug does to the body.
What is pharmacokinetics?
It is what the body does to the drug.
What does pharmacokinetics include?
Absorbtion
Distribution
Metabolism
Execration
What is elimination?
Metabolism + excretion
Why is there some lag in the start of the curve of the time course of drug action (oral)?
Due to Absorption but in intravenous, there is no lag.
Where should the drug concentration be kept?
In the therapeutic window.
What is absorption?
Absorption is defined as the passage of a drug from the site of administration to plasma.
What are the main routes of administration of drugs?
- Sublingual.
- Oral
- Rectal.
- Local.
- Inhalation.
- Injections.
Does the sublingual route have any Barriers?
No
What are the internal routes of administration?
- Sublingual.
- Oral
- Rectal.
What are the external routes of administration of drugs?
- Local.
- Inhalation.
- Injections.
What are the factors that affect the rate of Absorption?
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.
What is the ionization constant (pKa)?
It is the pH at which the ionized and non-ionized forms of the drug are equal.
Are ionized forms lipid soluble or no?
Unionized forms are more lipid-soluble and rapidly absorbed.
Where do acidic drugs become more ionized?
In basic media and vice versa
Give an example for acidic and basic drugs respectively?
Aspirin - amphetamine
What is the clinical significance of pKa?
-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.
What is the action of local anesthetic?
They block voltage-dependent Na+ channels within the nerve fibers →↓ nerve conduction.
What is the clinical value of pKa in local anesthetics?
• 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.
What is the bioavailability of drugs?
it is the fraction of the drug that becomes available for systemic effect after administration. The bioavailability of drugs given i.v. is 100%.
What are the factors that affect drug bioavailability(oral)?
Factors affecting oral availability:
- The same factors of drug absorption.
- Hepatic first-pass metabolism for oral route
What is the definition of volume of distribution?
The apparent volume of water into which the drug is distributed in the body after distribution equilibrium
How is Vd calculated?
The total amount of the drug in the body
Vd = —————————————————————————— = L Plasma concentration of the drug after distribution equilibrium
