Alan Flashcards
(45 cards)
What is Pharmacodynamics?
What the drug does to the body.
The relationship between exposure to the drug and effect.
Concentration-response
What is Route?
The site through which the drug is administered
What is Enteral?
Administered via the GI tract; the drug becomes systemically available
What does systemically available mean?
It gets into the patients circulation and is disrupted around the body
What is Paternal?
Administration via a non-GI route that allows delivery into the systemic circulation
What is Topical?
Local administration; the drug does not enter the circulation.
The drug is administered directly to the site of action.
Summary of topical administration?
Limited systemic exposure meaning the drug is not going to result in large concentrations appearing in the patient’s plasma.
Why does topical result in a limited systemic exposure?
This could be because the drug is not absorbed from the site of administration or because a small dose is used.
Why are small doses used in topical administration?
because the drug is being administered directly to the site of action. Meaning you don’t need to give a large dose, to achieve a large concentration at the site of action.
Small dose distributed around the patient’s body = small concentration in the patient so the exposure to be quite small.
What is Percutaneous administration
Administration through the skin
What is subcutaneous administration?
Into the tissue, just beneath the skin layer. An example of parental administration.
What is intramuscular administration?
All the way through the skin, into the muscle tissue. An example of parental administration.
What is intravenous administration?
Into the veins. An example of parental administration
What is transdermal drug delivery?
this is when the drug diffuses through distinct layers of the skin, into systemic or blood circulation to provoke therapeutic effect.
Epicutaneous administration?
Applied on the surface of the skin
Advantages of topical administration?
Fast, local, avoids systmic side effects
What must you consider with Enteral administration?
The drug must survive the gastric acid, and must therefore be able to withstand the pH of the acid, in order to be absorbed from the small intestine.
Absorption is relatively slow (fastest with an empty stomach)
The drug must be sufficiently lipophilic or taken up by a transporter
What is First Pass?
Drug passes through the liver before entering systemic circulation.
Explain the route for first pass?
The drug is absorbed from the small intestine, enters the portal vein, then goes through the liver. It exits the liver by the hepatic vein, into the vena cava and around the systemic circulation.
Why is first pass undesired?
The liver is a site of most drug metabolism.
It prevents the absorption of the drug, from the small intestine into the systemic circulation because most of the drug is getting metabolised in the liver.
Systemic circulation therefore has no opportunity to distribute the drug to other tissues.
First pass reduces bioavailability (the fraction of the drug that gets from the small intestine to the systemic circulation.)
Disadvantages of first pass?
Reduces bioavailability
It might be drug specific
Saturable
Might be affected by liver disease.
What happens if the liver is diseased, concerning first pass?
The rate of metabolism is reduced causing first pass metabolism to also be reduced.
So more drug will enter the systemic circulation.
But more drug in the circulation could lead to adverse effects
What is Enterohepatic recycling?
When the drug passes through the small intestine and to the liver, some of the drug might get excreted into the bile duct and then excreted back into the small intestine, instead of going to the systemic circulation.
This allows the drug to be recycled.
So the exposure of the drug is prolonged
What is Enterohepatic?
Recirculation between the intestine and the liver.
