pharmacology Flashcards
what is pharmacology the study of?
AMUA
Actions
Mechanisms
Uses
Adverse effects of drugs
What 2 disciplines are pharmacology divided into?
pharmacodynamics (PD) and pharmacokinetics (PK)
What is the definition of a drug?
Natural/ semi-synthetic or synthetic substance that alters the physiological state of a living organism/ system.
What are the 3 names that drugs are given?
Chemical, non-proprietary (generic) and propriety (brand)
what is the definition of pharmacodynamics?
Pharmacodynamics is studying the effects of a drug on various systems in the body.
What does Pharmacodynamics look at?
It looks at:
how the drug binds to the target site and initiates changes in various systems to change their physiological state
It also explains why some drugs maybe more potent than others or why different doses maybe needed
Drug binds to receptors to initiate changes in cells leading to therapeutic/ adverse effects. what are the 3 types of receptors?
Agonist
Partial agonist
Antagonist: competitive or irreversible (non-competitive)
What is the definition of Pharmacokinetics?
Pharmacokinetics is a fundamental scientific discipline that underpins the administration of drugs
What does Pharmacokinetics follow?
It follows a drug from the moment that it is
administered up to the point at which it is completely
eliminated from the body
What is a short definition of pharmacokinetics and pharmacodynamics?
Pharmacokinetics - what the body does to the drug/ substance
Pharmacodynamics - what the drug/ substance does to the body
What are the 4 main principles of Pharmacokinetics?
ADME
Absorption
Distribution
Metabolism
Elimination
What does absorption refer to?
Refers to the amount of drug
in general circulation
bioavailability
what is bioavailability?
The fraction of drug available to produce an effect
Amount of drug in general circulation
F = ——————————————–
Amount of drug administered
What are 3 mechanisms of drug transfer?
Passive diffusion
Active transport
Facilitated transport
what are 3 basic concepts of Pharmacokinetics?
Drug transfer
Drug properties
Effect of pH
What makes up drug formulations?
Solid/ semisolid
Liquid: suspension, solution
Polymer
What makes up Drug chemistry?
Molecular size and shape
State of ionization
Lipid – water partition coefficient
what influences the degree of dissociation?
pH of solution
pKa of the drug (dissociation constant)
What happens when ionized drugs become trapped in certain areas?
They cannot diffuse anymore thus reducing the amount of drug available to produce an effect
What is the clinical importance of absorption?
different routes of administration can maximize drug bioavailability
What effects do changes in bioavailability have on drugs?
Loss of drug effectiveness
drug toxicity
what are common routes of administration?
Enteral administration
- oral – po
- rectal
- sublingual, buccal
Parenteral administration - routes other than the digestive tract
- intravenous – iv (bioavailability 100%)
- intramuscular – im
- Subcutaneous – sc
- transdermal
- inhalation
- topical
- intrathecal (CSF)
What is used as an index of drug concentration in tissue?
Plasma concentration
what is the Volume of distribution?
Theoretical volume (in L) into which a drug dissolves to produce the plasma concentration observed at steady state
What is the clinical importance of volume distribution?
changes in VD influence plasma concentration of drug and dose may need adjusting
What is lipophilic?
Lipid soluble
Which molecules can be eliminated from the body?
only water soluble molecules
Where is a major site of metabolism?
The liver
but can also occur in the kidneys or lungs
What is metabolism influenced by?
Interaction with other drugs/ supplements
Ageing
Diseases (mostly important liver disease)
Genetic polymorphism
What are common methods of drug elimination?
Renal
Pulmonary
Biliary
Sweat, tears
Breast milk
only hydrophilic molecules can be excreted
What are the 2 types of time dependent patterns of drug elimination?
first order and zero order kinetics
What is first order kinetics?
Constant fraction of drug eliminated per time.
rate of drug elimination proportional to drug plasma concentration.
graph - curved
What is zero order kinetics?
constant amount of drug eliminated per time
Rate of drug elimination independent of drug plasma concentration.
Graph: straight line
What is the clinical importance of 1st order kinetics?
Time to eliminate drug independent of dose
Increasing dose or frequency of administration produces predictable rises in plasma concentration
Majority of drugs use first order kinetics
What is the clinical importance of zero order kinetics?
Time to eliminate drug dependent of dose
Increasing dose or frequency of administration produces unpredictable rises in plasma concentration
Makes drug administration complicated
what are Important parameters of 1st order kinetics?
- Elimination rate constant ke: describes the fraction of drug eliminated per unit time
- Half-life: interval of time to reduce the plasma concentration by one half
Half life in zero order kinetics is independent of dose but is useful to estimate?
time to clear drug from body
duration of action
time to achieve steady state
dosage interval to maintain steady state
Assuming intact renal and hepatic function.
What is the time needed to reach steady state plasma concentration after a single dose or how long does it take to clear a drug from the body?
4 - 5 half lives
What is the definition of clearance?
volume of plasma from which the drug would be removed per unit time
Expressed in ml/minute
Which is the most direct route of drug administration?
Oral
Intravenous
Intrarectal
IV
True or false:
Reactions of second phase are compulsory in drug metabolism before excretion.
false
True or false?
Zero-order kinetics does not depend on dose.
False - first order is dose-independent
What does ADR stand for?
Adverse drug reaction
What are adverse drug interactions we need to think about when giving contrast?
contrast media alone
interactions with drugs
What are the 2 types of drug interactions?
PD - Pharmacodynamics
PK - Pharmacokinetics
What are the risks of contrast and drug interactions?
Reduce renal function with reduced drug excretion
Enhanced contrast media renal effects
Enhanced allergic-like reactions to contrast media
Enhanced contrast media cardiac effects
Interference with hematological effects of contrast media and Contrast media and neuroleptic drugs
Which drugs can reduce renal function and therefore reduce drug excretion?
metformin and lithium
Which drugs can cuase enhanced contrast media renal effects?
NSAIDs, gentamicin, chemotherapeutic drugs, diuretics
Which drugs can enhance allergic-like reactions to contrast media?
alpha-receptor blockers (beta-controversial), interferons, interleukins, hydralazine
Which drugs can enhance contrast media cardiac effects?
high osmolar contrast media and calcium blockers
Which drugs can Interfere with hematological effects of contrast media?
(coagulation and fibrinolysis)
e.g. anticoagulants and antiplatelets
