Flashcards in Topic 2 Deck (16):
Many factors influence distribution, such as
the presence of protein and fat molecules in the blood that bind to the drug molecules and preventing them from reaching their sites of action.
What hurdle do drugs destined for the central nervous system (brain + spinal cord) face
the blood-brain barrier (a nearly impenetrable barricade)
What is the blood-brain barrier
a tightly women mesh of capillaries cemented together to protect the brain from potentially dangerous substances, such as poisons or viruses.
What must drugs be to enter the brain and why
drugs must be lipid soluble as the only means of passage into the brain is through the cell membrane
What happens in some disease states, such as infections of the brain
the capillaries become leaky allowing the entrance of substances normally excluded, such as penicillin
What is the major determinant of how a drug is distributed
its affinity for various tissue components such as fats, proteins or water.
Many drugs are attracted to and bind to what in the blood
proteins in the blood, collectively known as plasma proteins
What effect does drugs binding to plasma proteins have and why
has the effect of trapping the drug in the bloodstream, as plasma proteins are too large to move across or between the cells that make up the blood vessel wall.
What does the limited supply of plasma proteins mean
there is often competition between drugs and those with greater affinity, or more attraction will displace those with lesser affinity for the protein.
What is a key feature of drug distribution
Why is it important to know whether a drug has affinity for protein binding
as this influences the effective dose of the drug.
What is a potential source of drug interactions if multiple drugs are taken
What does displacement of drugs from proteins do + dangers of this
increases their availability at the sites of action and may result in dangerously high levels that are capable of producing toxic effects.
Why is displacement of drugs dangerous
as it increases their availability at sites of action which may result in dangerously high levels that could produce toxic effects.
As many drugs are lipid soluble, what may happen in the body
they may be attracted to fat stores in the body and during their passage around the body, the drugs may end up in fat stores.