deck_797765 Flashcards
Define pharmacokinetics
What the body does to a drug
Define pharmacodynamics
What the drug does to the body
Give four questions which should be asked when administering a drug,
Is the drug getting into the patient?(pharmaceutical process)Is the drug getting to the site of action? (pharmacokinetic process)Is the drug producing the desired pharmacological effects? (pharacodynamic process)Is the pharmacologic effect translated into a therapeutic effect? (therapeutic process)
What are the two methods of drug formulation?What is another factor on the administration of a drug?
Solid, liquidCompliance - simplified regime
If solid, what extra factors must be considered?
Solubility and acidic stability in stomach must be considered
Give two sites of administration?
Local (eye, skin, inhalation)Systemic (enteral or parenteral)
Give three examples of enteral systemic administration
Sublingual Oral Rectal
Give five examples of parenteral systemic administration
Subcutaneous/intramuscular/intravenous injection, inhalation, transdermal
Define the term oral bioavailability
Oral Bioavailability is the proportion of a dose given orally (Or by any other route other than intravenous) that reaches the systemic circulation in an unchanged form.
What can bioavailability be measured by?
1) Amount (depends on GI absorption and first pass metabolism)2) Rate of availability (depends on pharmaceutical factors and rate of gut absorption)
What are two factors which effect gut absorption?
Altered by food or disease
How is amount measured on graph?
Area under curve of blood drug level vs. time
How is rate measured on a graph?
peak height and rate of rise of drug level in blood
What is maximum tolerated dose?
Lethal Dose to 50% of people
What is minimum effective dose?
Effective Dose in 50% of people
What is the equation for measuring therapeutic ratio?
Maximum Tolerated Dose/Minimum Effective Dose(LD50/ED50)
Advantage of local admin?
Less systemic side effects, more direct action
What is the first pass effect?
Substances absorbed from the lumen of the ileum enter the venous blood, which drains into the hepatic portal vein and is transported directly to the liver. Liver is main site of drug metabolism, so any drug which enters it may be extensively metabolised before it reaches systemic circulation - first pass effect
How can the first pass effect be avoided?
The parenteral, sublingual or rectal routes can avoid it.Glyceryl trinitrate is a particular example
How much of an oral dose of paracetamol is metabolised via first pass effect?
90%
Define drug distribution
The theoretical volume into which a drug has distributed assuming that mixing occurs instantaneously
What is drug distribution calculated by?
mount Given / Plasma Concentration at Time 0
What happens to many drugs once they reach circulation?
Protein binding interaction - this is significant as it is the free concentration of drug which has an effect, not the total
What does rate of action depend on?
Dissolution