Pharmacokinetics Flashcards
(11 cards)
What is pharmacokinetics?
The effect of the body on the drug.
What is pharmacodynamics?
The effect of the drug on the body.
What factors affect the amount of drug which reaches a site of action?
Rate of: Absorption of the drug Distribution around the body Metabolism by the body Excretion by the body
What are the 4 main routes by which drugs cross cell membranes?
- Passive diffusion through the bilayer
- Diffusion through aqueous pores in the membrane
- Diffusion through intercellular pores
- Carrier-mediated transport
Describe how passive diffusion of drugs occurs across the cell membrane.
This is the most common route for drugs.
Molecules move down a conc. gradient.
Rate is proportional to lipid solubility, SA, and size of conc. gradient.
Describe how drugs diffuse through aqueous pores in the membrane.
Cells allow water to pass across the membrane. Small drug molecules can diffuse this way, but most are too big.
Describe how drugs diffuse through intercellular pores.
Some drugs move through intercellular pores.
Describe how drugs move via carrier-mediated transport.
Trans-membrane carrier proteins undergo a conformational change on binding to the substrate.
This allows the substrate to dissociate from the carrier on the opposite side of the membrane.
The substrate moves from high conc. to low conc. Some carrier-mediated transport systems are directly coupled to a supply of energy provided by the hydrolysis of ATP and can transport substrates against a concentration gradient (Active transport systems) Drugs are chemically similar to endogenous substrates
What are the 2 routes of drug absorption?
- Enteral - GI route
2. Parenteral - non-GI route
What are the routes of enteral administration?
Oral
Sublingual
Buccal
Rectal
What are the routes of parenteral administration?
Injection
Inhalation
Percutaneous
