Pharmacokinetics Flashcards
What is a drug?
A substance used for treatment, relief, diagnosis or prophylaxis of a disease
What are the 3 sources where drugs can come from?
Plant
Animal
Mineral
How do enteral drugs enter the body?
Anything involving digestive tract. Mouth to rectum
Where do parenteral drugs go?
Avoids the gut so any route other than via gastrointestinal tract
Give examples of parenteral drugs? ( not through digestive tract )
Transdermal - patches
Implantation
Intramuscular - muscle
Intrathecal - spine ( epidural )
What does TOP TIPS stand for?
Tropical, oral, parenteral, transdermal, inhalation & subcutaneous ( under the skin )
What is a subcutaneous drug?
Applied under the skin
What is the pharmacokinetic phase?
ADME
Absorption
Distribution
Metabolism
Excretion
Absorption across cell membranes involves what transports?
Passive - no energy required. Movement from a high to low concentration
Active - energy is required. Drugs move against the concentration gradient
Factors that may affect the absorption of drugs across the GI tract?
Drug preparation - how quickly it disintegrates
Interaction - pH of stomach contents, food and other drugs
Physiological factors - how quickly the drug is moved through the digestive tract
How does blood flow to a tissue affect distribution?
Drugs will reach higher concentrations in tissues which have a good blood supply eg, Brain. However, reduced flow to tissues and organs will affect distributions eg, blood brain barrier
Some substances blocked from entering the brain tissue?
Toxins, some drugs and specific bacteria
What is the first pass effect?
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
If taken orally, where is the tablet absorbed across??
The wall of the stomach and / or the small intestine
What is biotransformation?
The conversion of molecules from one form to another within an organism, often associated with change in pharmacological activity
What are the main organs involved in elimination of drugs?
But, Skin, Lungs, Salivary grands, sweat glands, breast milk and Kidneys
What is bioavailability?
Describes the fraction of administers dose of the drug that reaches the systemic circulation
How much bioavailability of a drug is there when it’s administer intravenously ( vein )?
100%
Why does propranolol have a bioavailability of 25%?
Because 75/85% is metabolised via 1st oasis effect ( metabolised by liver ) if taken orally before it can reach the circulation
Why is morphine usually given via intramuscular injection?
Takes longer for plasma concentration to reach and it lasts longer
What does onset mean?
Time from administration to when the therapeutic effect occurs
What is a modified release?
Designed to slowly release drug into the gastrointestinal tract over a period of time
What is a therapeutic range?
Optimum plasma level in which it has its therapeutic effect
What is a therapeutic window for a drug?
Describes the levels in plasma which a drug can act
What organs are most likely to be affected by drug toxicity?
Liver and kidneys
Name a withdrawal symptom that can be experience when stopping opioids ( heroin and morphine ) after a long period of time?
Headaches
Pharmacokinetics is?
How the body handles the drug
Tolerance is?
A decrease in pharmacological effect when a drug is given repeatedly
Modified release predations are designed to?
Slowly release drug over a period of time
What happens to the drug in the liver?
Metabolic processes will convert the drug into a more water-soluble compound by increasing its polarity
Name a drug sourced by a plant origin?
Digoxin
