Pharmacology Flashcards
What is a medicinal product?
- Any substance or combination of substances presented for treating or preventing disease in human beings or animals
What is medicines management ?
- The clinical, cost effective and safe use of medicines to ensure patients get the maximum benefit from the medicines they need, while at the same time minimising potential harm.
What is pharmocology?
Pharma = drug Ology = Study off
- It is the science that looks at the composition effects of an uses of different drugs.
- A drug is any chemical that affects any living organism
What is pharmacodynamics?
- This describes the action of a drug
- The mechanism of effects the drug has on the body - at a molecular, cellular and tissue systems level
- for example a drug may be given for therapeutic action which aims to reverse or modify changed to regain homeostasis
What is the receptor theory (lock and key)?
Transmitter = the key Receptor = the lock
- When the key opens the lock we get an action
- Signal molecule
- binds too
- Receptor protein
- activates
- Intracellular signal molecules
- alters
- Target proteins
- create
- Response
How does adrenaline increase your heart rate?
- Adrenalin (the key) is released by the adrenal medulla
- Travels to the heart and acts on the alpha and Beta receptors (lock)
- This increases the heart rate and force of contraction ( outcome)
- Adrenalin in this pathway is referred to as a signal molecule
What are receptors?
- These are glycoproteins in cell membranes that recognise and bind to ligands
- Ligands are smaller molecules (e.g drugs) that are are capable of ‘ligating’ themselves to the receptor protein
Binding = shape change of receptor = generation of biochemical reaction inside the cell known as (‘ Signal transduction’) leading to several reactions called ‘secondary messengers’ that is eventually translated into a biological response e.g muscle contraction, or hormone secretion
- The more receptors involved the bigger the response
What is pharmacokinetics?
- This is the movement of drugs inside the body
This includes: - Absorption = A - medication at site of administration
- Distribution = D - medicine in plasma (medicines in tissue)
- Metabolism = M- medicine in plasma (metabolites in tissue)
- Excretion = E - medicine and metabolites in urine bile or faeces
(ADME)
A knowledge of both pharmacodynamics and pharmacokinetics is essential to understand what drugs do and how they do it
What is drug absorption?
Drugs must cross biologic barriers e.g epithelial/ endothelial
- This can be done in two ways:
1- active transport
2- Passive diffusion
What is active transport?
- Movement across a cellular barrier
- It requires ATP to move the drug from a lower concentration to a higher concentration
What is passive diffusion?
- Cross cellular barriers
- Moves from an area of high to low concentration by simple diffusion
- However this is dependent on the chemical size, Ph, solubility of drug, surface area for absorption (e.g villi/ microvilli ) vascularity, presence or absence of food in stomach and presence of enzymes, acidity
- Most drugs are distributed via diffusion
What factors affect drug distribution?
- Small molecules diffuse more rapidly the large
- Ph effects the nature and absorption of the drug e.g acid drugs are better absorbed in an acid medium and base drugs are better absorbed in abase medium.
- Cell membranes are mainly lipid ( fatty_ materials. Only lipid like substances (lipophilic ) substances can cross easily and rapidly
- Most drugs act on receptors (usually protein)
- Factors such as the chemical nature of the drug and route of administration wil determine distribution of the drug.
What is drug ,metabolism?
- Drug metabolising enzymes have evolved as a defence against non-medical chemicals taken up from the environment and can be found in organs e.g skin, lungs, kidneys
- Drugs are chemically broken down into the liver by cytochrome P45O enzymes and made water soluble to be extracted via urine
- Chemical modifications higher or lower a drugs pharmacological activity and/or half life
What is an agonist?
- These bind to receptor proteins= produce a conformational change to enhance a biological response.
- When a drug stimulates the receptors it is an agonist
- An example would be Adrenaline
What is an antagonist?
- These bind to receptor proteins but do not produce the conformational change that initiates an intracellular signal
- Occupation of the receptor by a competitive antagonists, prevents binding of other ligands and so antagonises the biological response.
- An example of this is MORPHINE
Agonists and antagonists are influenced by affinity
What is affinity?
- This can be defined as the tenacity (persistence)with which a drug binds to its receptor
What is efficacy?
- This is the ability of a drug ti produce a maximum response
What is potency?
- This is the amount of drug required to produce an Effect of given intensity
what does the liver do in terms of metabolism?
- Most substances that are absorbed from the GI tract are taken up by the partial system- this includes drugs
- The substances are taken to the liver to be processed/ stored and metabolised
- Some drugs are metabolised so well in the liver that they cannot be given orally
What is the blood brain barrier?
It is made up of cerebral capillaries ( which are different from those in the body)
- Endothelial cells of cerebral capillaries are really close together
- This along with the connective tissue cells of the CNS form a barrier between blood and brain many molecules are prevented from travelling to brain tissue
- Only some substances can actively cross the barrier this has advantages and disadvantages
- Substances that can pass across the blood brain barrier include O2, CO2, glucose, amino acids alcohol and nicotine
- Lipid soluble substances cross very easily
- Metabolic waste products such as urea and creatinine cannot move through the productive mechanism
what can cause the blood brain barrier to open?
- Microwaves
- Radio waves
- Trauma
- Hypertension
- Infection
What are 2 other barriers in the body?
Placental
- Most drugs cross this barrier and may cause congenital malformation
Testicular
- Protects spermatogenesis from blood bounce chemicals little is understood about this barrier
What is drug half life?
- This is the time taken for the concentration of a drug to decrease by half
- If blood concentration of drug X I’d 1000mcg/ L any a certain time and after 4 hours it is 500mcg/L the drugs half life is 4 hours another 4 hours and it will be 250mcg/L
- Half life is used in calculating when repeated doses should be given.
What is bioavailability?
- This is the proportion of the drug that reaches the circulation
- Intravenous drugs have a bioavailability of 100%
- A swallowed drug has only a proportion of this however the oral administration is probably the most common route of administration
What is the steady state?
The intention is to achieve a steady state concentration
- Half life of 48 hours would take 2 weeks to reach a steady state
- Half life of 2 hours would take less then a day to reach steady state
- A loading dose can help achieve Tiguas in drugs with a larger half life
- For all drugs there is a min effective concentration (MEC) and a max effective safe concentration (MSC)
What Is therapeutic index?
- This is the ratio of dose that produces toxicity to dose which produces a clinically desired or effective response
- It provides a measure of drug safety
- Large index (ratio)= wide margin to reach toxic levels
- Small index (ratio)= toxic levels quickly reached
Individual patient variation more likely in drugs with a small index as effective and toxic plasma concentrations are similar
E.G penicillin - large index
Warfarin - small index is the toxicity levels are regularly monitored
What are antimetabolites?
These drugs closely resemble substances required for cell metabolism/ nutrition
What are Enzyme inhibitors?
- These drugs interfered with action of the body enzymes Therefore preventing certain chemical reactions/ processes from occurring
What are action cell membrane drugs?
These are drugs that interfere with the chemical activity of cell membrane and prevent function
What are replacement deficiencies?
Here drugs replace a dietary factor pr hormone that is essential for normal function
What is cytotoxic effect
Used to kill bacteria or malignant cells without undue harm to other cells.
Interference with cell activity may occur and multiplication stopped.
- Various cytotoxic drugs have differing specific effects/ actions
What is total body clearance?
- This is achieved by a combination of action by the liver and kidneys
- The lover assists with clearing by metabolising and one excreting drugs through bile. Drugs can therefore be excreted in faeces or reabsorved witching liver the to be excreted via the kidney
- In certain instances lungs were the main organs of elimination
What is drug excretion?
- Drugs can leave body in saliva, sweat, tears and breath
- Excretion of alcohol by the lungs is the reason why breath testing detects alcohol levels
- Majority or drugs are excreted unchanged as metabolites in urine or bile
- Patients with kidney or lover problems need careful consideration in drug therapy and often have reduced doses
