Pharmacokinetics Flashcards
Define pharmacokinetics.
What the body does to the drug.
Define what a drug is.
It is any substance used for the treatment,relief,diagnoisis or prophylaxis of disease.
Give examples of drugs which have derived from plants.
Opium poppy,digoxin.
Give examples of drugs which have derived from animals.
Warfarin,fish oil.
Give examples of drugs which have derived from minerals.
Magnesium,Kaolin.
Give examples of drugs used in treatment,prevention and diagnosis.
- Antibiotics-NSAIDs
- Warfarin
- Barium
What does the term enteral route of administration mean?
This refers to anything involving the digestive tract, from the mouth to the rectum.
What does the term parenteral route of administration mean?
Literally means to avoid the gut and refers to any route of administration other than via the GI tract.
List as many routes of administration as you can.
- Subcutaneous
2.Intramuscular
3.Intravenous
4.Transdermal
5.Implantation
6.Oral
7.Topical
8.Rectal
9.Vaginal
10.Inhalation
11.Parenteral
TOPTIPS
Name the four phases in drug administration.
- Absorption
- Distribution
- Metabolism
- Elimination
Describe the term absorption in relation to administration.
It is the process from administration till it reaches the tissues and is available for use. This may involves getting into the circulation though not always as in the case of inhaled drugs or topical cream. Oral drugs have to be converted to a soluble state so it can be quickly absorbed.
What is the difference between passive and active transport in relation to absorption across the membrane.
Passive transport requires no energy and is the movement of a substance from a high to a low concentration. Most drugs are absorbed this way.
Active transport requires energy as drugs move against the concentration gradient. One drug that does this is called levodopa used to treat Parkinson’s disease.
List factors that influence the absorption of drugs across the GI-Tract.
- Drug preparation- Capsules,enteric coating,controlled release.
- Interactions- pH of stomach contents,food,other drugs.
- Physiological factors- How quickly the drug is moved through the GI tract e.g. Age,Diarrhoea,disease state.
How does the body distribute drugs around the body?
Via the bloodstream.
What prevents substances from entering the central nervous system, and how?
Blood brain barrier
The brain capillaries have a dense-walled structure and are surrounded by glial cells. This prevents drug molecules from entering surrounding tissues.
What is a free drug ?
A free drug is the part of the drug that is not bound to a plasma protein (albumin) but can exert its effect on tissues.
Where is the main site of drug metabolism.
The Liver
Why do drugs need to be metabolised?
Drugs need to transformed so it is more water-soluble and can be excreted.
What is the first pass effect?
This describes the effect liver metabolism has upon the drug during its first passage through the liver, and in particular how much of the drug is inactivated.
The first pass effect will determine:
The amount of drug reaching to general circulation
The half-life of the drug
Whether the drug undergoes ‘biotransformation’
What does the half-life of the drug mean?
The time taken to eliminate half the drug from the plasma.
Define biotransformation.
The conversion of molecules from one form to another within an organism.
In the case of drugs, it may involve the drug being changed from an inactive state to and active state. These are called ‘pro drugs’.
Define excretion.
It is the removal of active or inactive drugs from the site of action.
List the main organs involved in elimination of drugs.
- Skin
- Gut
- Liver
- Lungs
- Sweat
- Breast milk
- Glands
Define bioavailability.
It describes the fraction of an administrated dose of the drug that reaches the systematic circulation.
