Drug Distribution Flashcards
Various routes are used to administer Drugs. But how do most drugs reach site of action?
via Systemic circulation.
What is Plasma?
Plasma is the liquid part of your blood and makes up about 55% of the volume. It carries cells and platelets arround the body. 7% are plasma proteins.
What are Plasma Proteins?
Plasma Proteins are molecules found in blood plasma. Most but not all are made in the liver.
Types- Albumin form 60% and most abundant
Globlins form 35%
Fibrogins approx 4%
Metabolic enzymes 1%
Which Plasma Proteins help control Osmotic Pressure?
Albumin contribute to osmotic pressure, help to control water balance and are involved in the transport of substances in blood including drugs.
What do Globulins do?
Globulins can transport fat and proteins, aid with clotting and are essentian for fighting of infection and keeping our liver and kidneys healthy.
What are Fibrinogen?
Produced in the liver- produces a mesh like structure at site of injury to stop bleeding/
what is the main influence of Plasma proteins on Drugs?
Distribution.
Drug absorption and elimination
Extensive plasma protein binding will increase the amount of drug that has to be absorbed before effective therapeutic levels of unbound drug are reached. For example, acidic dugs (such as acetyl salicylic acid – aspirin) are often substantially bound to albumin.
Elimination of a highly bound drug may be delayed. Since the concentration of free drug is low, drug elimination by metabolism and excretion may be delayed. This effect is responsible for prolonging the effect of the drug digoxin.
How does age impact on drug effects?
Increased age or malnutrition can mean low plasma protein level. Also liver disease can affect prodction.. Or kidney failure where there are changes in excretion of albumin.
This can result in smaller ammount of drug bound to protein and more free drug- meaning greater therapeutic effect- even toxicity. reduced dosed may be indicated.
