Pharmacology Flashcards
What is pharmacology
Study of drug action on the body
What is pharmacokinetics
The study of what the body does to a drug
What is pharmacodynamics
Physiological effects of a drug on the body
What does ADME mean in pharmacokinetics
Absorption
Distribution
Metabolism
Excretion
If a drug is given orally, where does it go
GI tract
What happens when a drug is absorbed by the GI tract
Goes to the liver where some drugs are broken down
How can elimination happen
Broken down by liver
Excreted by kidneys
Excreted via lungs
Where does pharmacological action happen
Circulation tissue space
What is absorption
Rate and extent at which a drug leaves its site of administration and enters the circulatory system
What can impede the efficacy of a drug
Route of administration e.g. orally or rectally
What can enhance or impair the rate of absorption
Presence of food
What happens when the GI tract is compromised
A parenteral route must be considered
Why does location of drug administration need to be considered
Tissue perfusion will also impact on absorption
What is first pass effect
When a drug has been absorbed into circulation it is transported to the liver via hepatic portal system where it is metabolised
Why do we have to reduce the amount of active drug being distributed within the body
Because some drugs undergo extensive hepatic metabolism
What is produced by first pass effect
Drug and metabolites
How can first pass effect be avoided
Using parenteral route which bypasses this process and provides body with a more accurate dosage
Once a drug has been metabolised by the liver, where does it go
Enters the systemic circulation and travels in the plasma to its site of action
What happens once a drug has reached the desired site of action
It leave the plasma and enters interstitial fluid then the cells and combines cellular receptors to create an action
What affects drug distribution
Drug formulation
Blood flow to that area
Binding/unbinding of the drug to plasma proteins
Presence of anatomic barriers
What are fat loving drugs
Lipophilic
What are water loving drugs
Hydrophilic
Which route of administration is best for hydrophilic drugs
IV, IM as they enter the extra cellular fluid
Which route of administration is best for lipophilic drugs
Orally or SC as needs rap diffuse through a cell membrane
When are drugs most rapidly distributed. Give examples
When entering well perfused tootsies e.g. active skeletal muscle, liver, kidney, brain
Which tissues are poorly perfused
Inactive skeletal muscle and adipose fats
What remains in the circulation as a reservoir for circulating drugs
Plasma proteins
What happens when a drug binds with a plasma protein (albumin)
Termed inactive and unable to migrate into the tissues to exert its effect
What happens to drugs that do not bind to plasma proteins
Able to migrate into tissues and exert effect
What happens to the amount of unbound and bound drug after plasma protein binding
Drug within circulation will remain the same
What happens to bound molecules when unbound drug molecules move into tissues during plasma protein binding
Bound molecules are released to maintain the balance
Why is protein binding significant
Because plasma protein levels are reduced due to disease as the standard dose could cause toxic concentrations
Which organs can cause toxic concentrations of drugs
Liver, GI, kidney
Why are anatomical barriers important
In the capillaries of the CNS as endothelial cells in the brain are closely packed together preventing some drugs from entering
What type of drugs can cross the blood:brain barrier
Lipophilic
What happens to drugs before they can be excreted
Biotransformation / drug metabolism
Where does bio transformation happen
Generally in liver (lungs and kidneys)
What happens when drugs are metabolised
Enzymes modify the molecules of the drug to enable elimination
What does enzyme action do during metabolism
Provokes chemical reactions that cause drug to become hydrophilic enabling drug to be eliminated by kidneys
Factors affecting drug metabolism
Species, age, nutritional status, health status
Where does excretion take place
Liver, lungs, skin, glands e.g. mammary, sweat and salivary