Pharmacology Flashcards
Physicochemical
Drug reactions Adsorption Precipitation Chelation Neutralisation
Pharmacodynamics
drugs effect on the body
Pharmacokinetics
body.’s effect on drug
Treatment for paracetamol overdose
Activated charcoal - binds to paracetamol (adsorption) and then leaves the body like this
Treatment for opioid overdose
Naloxone
Pharmacodynamics pathways
Summation
Synergism
Antagonism
Potentiation
Pharmacokinetics pathways
ADME - Absorption, Distribution, Metabolism, Excretion
Drugs tend to be metabolised in
Liver
Kidneys
Lungs
Codeine
Metabolised into morphine
Codeine is essentially low-dose and slow-releasing morphine
Bioavailability
Comparison between how much oral drug vs IV drug makes it into the system (blood)
IV > Oral for bioavailability
Morphine side effects
Slows down gut motility and so level of adsorption (Para NS affected)
Acidity
Drug is split into 2 portions - ionised and unionised (tends to be equilibrium)
Unionised portion can coss through the phospholipid bilayer
Distribution - pathway of drug
Protein binding
Tissues
Effect sites
Volume distribution
Bigger VD = not much in blood
Lower VD = mostly in blood so more reaches effect site
Protein binding
How much drug can bind to protein
Metabolism
Morphine metabolised in Liver by CYP450 and then broken down into morphine-6-glucuronide (much more potent than morphine itself),
Anti-epileptic drug (acute epilepsy)
Phenytoin
Enzyme inhibition and induction
counter mechanisms of enzyme action
Warfarin
Warfarin inhibits vitK factors in coag cascade
it is highly protein bound and is affected by enzyme induction which causes it to have less of an effect.
Metronidazole inhibits this and so more warfarin is about in blood which can be toxic
AKI (acute kidney injury) -causing drugs
NSAIDs, ACEi, Furosemide, Gentamicin
Grapefruit juice
Interacts with warfarin by protein binding and CYP450 pathway
Excretion
Mostly extracted via kidney
Druggability
The ability of a protein target to bind small molecules ith high affinity
Also known as ligandability
Drug targets
Receptors
Enzymes
Transporters
Ion channels
Receptors
Component of a cell that interacts with a specific ligand and initiates a chain of biochemical events leading to ligand observed effects
Chemicals communicate via receptors
Ligands can be
Exogenous (drugs)
Endogenous (hormones, neurotransmitter)
Neurotransmitters
Acetylcholine
Serotonin
Hormones
Testosterone
Hydrocortisone
Autacoids (local)
Cytokines
Histamine
Receptor types
Ligand-gated ion channels (Nicotonic ACh receptor)
G protein-coupled receptors (Beta-adrenoreceptors)
Kinase-linked receptors (Growth factor receptors)
Cytosolic/nuclear receptors (steroid receptors)
G protein-coupled receptors
One of the most common group of membrane receptors
7 membrane-spanning receptors
Ligands include light energy, peptides, lipids, sugars and proteins
G proteins (GTPases) act as molecular switches. (On when bound to GDP, off when bound to GTP)
G proteins are guanine-nucleotide binding proteins which transmit signals from GPCRs
GPCR pathway
Ligand
Receptor G protein
Coupled receptor
2nd messenger
Kinase linked receptors
Transmembrane receptors activated when the binding of an extracellular ligand causes enzymatic activity on the intracellular side
Nuclear receptors
Work by modifying gene transcription
Steroid hormones
Tamoxifen (breast cancer) acts as a selective oestrogen receptor modular (SERM), or as a partial agonist of the oestrogen receptors
Chemical imbalances can lead to pathology
Allergy - increased histamine
Parkinson’s - reduced dopamine
Receptor ligands
Agonist - Compound that binds to and activates receptor
Antagonist - Compound that reduces the effect of an agonist
Potency
EC50 - Conc that gives half the maximal response
Full agonists
Complete saturation
Partial agonists
Never reaches complete saturation
Efficacy/Intrinsic activity
Max response achievable from a dose
Potency vs efficacy
Drug may be potent but not efficacious and vice versa
Competitive antagonism
Antagonist reverses the effects of agonists
Non-competitive antagonist
Molecule binds to an allosteric (non-agonist) site on the receptor to prevent activation of a receptor
Cholinergic receptor types
Nicotinic (agonist), curare (antag)
Muscarinic (agonist), atropine (antag)
Histamine receptor types
All are GPCRs H1 - H2 - Contraction of ileum, acid secretion from parietal cells (agonist), Cimetidine (H2 antagonist) H3 - H4
Affinity
How well a ligand binds to the receptor
Efficacy
How well a ligand activates a receptor
Antagonists
Have affinity but zero efficacy
Agonists
Have affinity and efficacy
Isoprenaline
Non-selective beta-adrenoreceptor agonist
Irreversible antagonist
BAAM
Receptor reserve
Where agonists need to activate only a small fraction of existing receptors to produce a maximal response, so spare receptors leftover (reserve)
Signal transduction (amplification)
Signaling cascade causes amplification of a signal and a response
Allosteric modulation
The ligand binds to site other than the active site of receptor and elicit a different response through a structural modification due to the binding at the allosteric site
Inverse agonism
When a drug binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist
Tolerance
Reduction in agonist effect over time
Continuous, repeated high concentrations
Desensitisation
Uncoupled protein is internalised and degraded
Salbutamol
B2-adrenoreceptor agonist
Streptokinase
Clot buster - degrades a clot
Enzyme which is a drug product
Statins
HMG-CoA reductase inhibitors
Block the rate-limiting step in the cholesterol pathway
A class of lipid-lowering medications that reduces the level of bad cholesterol
Primary prevention of CV disease
ACEi
Increased blood pressure via the RAAS pathway
Increases amount of salt and water retained by the body
Inhibiting ACE reduces AT2 production and therefore causes this reduction in BP
Parkinson’s disease - Symptoms
Hypokinesia
Resting tremor
Muscle rigidity
Cognitive impairment
Parkinson’s disease - Treatment
Substrate - L-DOPA is a precursor for dopamine biosynthesis which crosses the blood-brain barrier (BBB)
Drugs and ion transport
Passive - Symporters, channels
Active - ATP-ases
Protein ports
Uniporters - uses ATP to pull molcules in
Symporters uses movement of a molecule to pull in another against conc grad
Antiporters - one substance moves against its gradient after the other moves down
Na-K-Cl cotransporter (NKCC)
Example of a symporter
Protein that transports Na, K and Cl into cells
Functions in organs that secrete fluids
Epithelial sodium channel
Membrane-bound ion channel
Causes reabsorption of Na+ ions at collecting ducts of kidneys nephrons
Blocked by high-affinity diuretic amiloride (often used with thiazide) - Anti-hypertensive
Voltage-gated calcium channels
Found in the membrane of excitable cells (muscle, glial, cells, neurons, etc)
At resting membrane potential, VDCCs are normally closed until activation resulting in depolarisation which then opens them
Amlodipine is an angioselective CCB that lowers BP
Voltage-gated sodium channels
Conducts Na+ through plasma membrane
Lidocaine blocks transmission of action potentials
Voltage-gated potassium channels
Sulfonylurea lowers blood glucose levels by blocking potassium channels (Treatment of T2DM)
Receptor-mediated chloride channel
GABA-A receptor
Barbiturates increase the permeability of channel to chloride ions
Sodium-Potassium ATP-ase Pump
Digoxin - Inhibits this pump mainly in the myocardium
Mainly used for AF and heart failure
Proton pump (stomach)
Omeprazole (PPI - 1st in class) - Inhibits acid secretion (finitely irreversible)
Irreversible enzyme inhibitors
Organophosphates (irreversible inhibitors of cholinesterase)
Xenobiotics
Compounds foreign to an organism’s normal biochemistry such as any drug or poison
Cytochrome P450
Membrane-associated proteins located in the inner membrane of mitochondria or in the endoplasmic reticulum of cells
Major enzymes involved in drug metabolism
Most drugs undergo inactivation by CYPs
Many substances are bioactivated by CYPs to form their active compounds
CYPs metabolise thousands of endogenous and exogenous chemicals
Naturally occurring opioids
From opium poppy
Naturally occuring opioids from opium poppy
Moprhine - strong
Codeine - weak
Chemically modified (simple)
Diamorphine
Oxycodone
Dihydrocodeine
Synthetic opioids
Fentanyl
Pethidine
Allentanil
Remifentanil
Synthetic partial agonists
Buprenorhine
Synthetic partial antagonist
Naloxone
Bioavailability
First pass metabolism by liver
50% of oral is metabloised by first pass
Routes of admin
IV fastest
Oral slowest
IV PCA
Patient-controlled analgesia
Opioid receptors are located in
Epidural/CSF
Transdermal patches for lipid-soluble drugs such as
Fentanyl
Opium contains
Morphine
Codeine
Controlled drugs legislation
Opioids class A drugs
Secure storage
2 signatures required
Dihydrocodeine
1.5 times more potent than codeine
Oxycodone
1.5 times more potent than morphine
Opioid pharmacodynamics
Natural endorphins (endogenous morphine) and enkephalins
GPCR - Via second messengers
Inhibit release of pain transmitters at spinal cord and midbrain - and modulate pain perception
How opioids work
Descending inhibition of pain
Part of fight or flight response
Never designed for sustained activation
Sustained activation leads to tolerance and addiction
Opioid receptors
MOP
KOP
DOP
NOP
Kappa agonists cause
Depression instead of euphoria
All drugs currently used are
U agonists
Potency vs efficacy
Potency - strong or weak, how well drug binds to receptor (binding affinity
Efficacy - Maximal response or not, Full or partial agonist
Opioid potency examples
Diamorphine (strongest)
Morphine
Pethadine (weakest)
Tolerance and dependence
Tolerance - down-regulation of receptors with prolonged use, need higher doses to achieve the same effect
Dependence - psychological (craving, euphoria), physical
Opioid withdrawal - lasts up to 72 hours
Side effects
Resp depression Sedation N and V Constipation Itching Immune suppression Endocrine effects
Opioid-induced resp depression
Call for help
ABC
IV Naloxone (titrate to effect), has a short half-life so wears off.
Opioids use in chronic non-cancer pain
Start to lose effectiveness quickly within weeks
Common opioids
Fentanyl
Tramadol
Pharmacogenetics
Codeine is a prodrug which needs to be metabolised by Cytochrome CYP2D6 to morphine to ork
CYP2D6 activity varies in the population - codeine will have a reduced or absent affect in some of the population
Metabolism of morphine
Morphine is mebtaolised to Moprhine 6 glucuronide which is more potent than morphine and is renally excreted
In renal failure it will build up and may cause resp depression
Tramadol
Weak opioid agonist Slightly stronger than codeine It is a Prodrug Interacts with SSRIs, take care when prescribing to patients on antidepressants Controlled drug
Summary
Oral bioavilability is 50% for oral morphine
Titrate the dose to suit patient
Potentil for resp depression
POtential for addiciton - be careful for starting strong opioids for chronic backache
Dont issue repat prescription without seeing patient
Blood pressure control
Raise it in shock
Lower it in hptn
Heart rate control
Speed up bradycardias
Slow down tachycardias
A drug to lower bp will
lower heart rate
Nicotine and curare
Nicotine activates neuromuscular junction
Curare opposed this activation
Vagal nerve stimulation
slows the heart
NS
Somatic - skeletal muscle
Autonomic - involuntary
Enteric - gut
PNS
Sympathetic
Parasympathetic
Sympathetic NS
Release noradrenaline which activates adrenergic receptors (alpha and beta)
Parasympathetic NS
Release ACh which acts on muscarinic receptors
Sympa vs Para NS
Both NS first release ACh but then para fibres then release Noradrenaline whereas sympa fibres releases ACh
Muscarinic receptors
M1-5
GPCRs
G proteins can activate second messengers
M1 - Brain
M2 - Heart (activation slows the heart)
M3 - Glandular and smooth muscle (bronchoconstriction)
M4/5 - CNS
Atropine
For life-threatening bradycardias and cardiac arrest
Muscarinic agonists
Pilocarpine - stimulates salivation (sjogrens syndrome),
Muscarinic antagonists
Atropine
Hyoscine
Hyoscine
Palliative care for drying secretions
Bronchoconstriction treatment
Ipratropium bromide - short acting
Tiotropium - long acting
Overactive bladder treatment
Solifenacin (anticholinergic)
ACh
Major transmitter innervating skeletal muscle
Anti-cholinergic side effects
Confusion
Constipation
Drying of mouth
Catecholamines
Noradrenaline - management of shock in ICU
Adrenaline - Anaphylaxis management
Dopamine
Signaling pathway
Receptor
Cell
G protein
Signaling receptors
Alpha 1 and 2
Beta 1, 2 and 3
Beta 2 is the only receptor where Adrenaline dominates over NAd
Alpha agonists
Septic shock treatment
Alpha 1 activation causes vasoconstriction
Alpha 2
Clonidine - Alpha 2 agonist (lowers BP)
Alpha 1 blockers
Blok alpha 1 to lower BP
Tamsulosin - treats prostatic hypertrophy
Doxazosin - Lowers BP
Alpha 2 blockers arent useful so dont learn them
Beta agonists
Beta 2 activation, muscle relaxation in asthma
However beta agonists cause tachycardia and affect glucose metabolism in liver (increases glcuose production)
Beta blockers
Propanolol - blocks Beta 1 and 2, slows HR, reduces tremor, may cause wheeze
Atenolol -Beta 1 selective, main effects on heart
Beta 1 and 2
Beta 1 mainly affects heart
Beta 2 mainly affects lungs
Uses of beta blockers
Angina MI prevention High BP Arrhythmias Heart failure
Beta blockers - side effects
Bronchoconstriction
Bradycardia
Hypoglycaemia
Cardiac depression
hYPERSENSITIVTY
iMMEDIATE
aCUTE
DELAYED
Antibodies
IgM - made at start of infection
IgE - allergies
Type 1 reactions
Acute anaphylaxis
Hay fever
Asthma
Atopy
An inherited tendency to exaggerated IgE response to antigen
Hay fever, eczema, asthma
Skin prick test
Check for allergic responses
Histamine
Drives allergic responsesT
Histamine
Drives allergic responses
Atopy diagnosis
Skin prick test
RAST test
Hay fever treatment
Antihistamines
Steroids
Anaphylaxis treatment
Adrenaline Fluids Bronchodilators Steroids Anti-histamines
Goodpastures syndrome
Autoantibodies formed - Type 2 reaction - Ig bound to surface antigens
Lung and kidney problems (pulmonary haemorrhage and glomeruloneprhtis (renal inflamamtion))
Treatment - remove anitbodies
Mycoplasma pneumonia
Causes pneumonia
Type 2 reaction
Causes haemolytic anaemia
Type 3 diseases
Endocarditis
Alveolitis
Type 4 reactions
Formation of granulomas
Slow process
Adverse drug reaction
Has to be noxious and unintended
Side effect
An unintended effect of a drug that can be beneficial
Tend to be minor and predictable
PDE5 inhibitors
Improve urinary flow
Adverse drug reactions
Toxic effects (beyond therapeutic range) Collateral effects (therapeutic range) Hypersusceptibility effects (below therapeutic range)
Toxic effects
Nephrotoxicity with high doses of aminoglycosides such as gentamicin
Dysarthria and ataxia with lithium toxicity
Cerebellar signs and symptoms with xs phenytoin
Tend to occur if drug doses are too high or renal/hepatic issues
Collateral effects
Standard therapeutic doses
Beta-blockers cause bronchoconstriction
Broad-spectrum antibiotics cause C difficile
Hypersusceptibility reactions
Subtherapeutic effects
Anaphylaxis and penicillin
Severity of ADRs
Mild - nausea, drowsiness, itching rash
Severe - Resp depression, neutropenia, haemorrhage, anaphylaxis
Time independent reactions
Occur at any time during treatment
INR increase when erythromycin administered with warfarin
Time-dependent reactions
Rapid reactions - red man syndrome due to histamine release with rapid administration of vancomycin
First dose reactions - Hypotension and ACEi
Early reactions - Nitrate induced headache
Intermediate reactions - delayed immunological reactions such as stevens-johnson syndrome with carbamazepine
Late reactions - adverse reactions of long term steroids
Rawlins Thompson classification of ADRs
Type A - Predictable, dose dependent, common
Type B - Bizzare, not predictable, not dose depedent
Type C - Chronic, osteporosis and steroids
Type D - Delayed, maligancies after immunosuppression
Type E - End of treatment, occur after abrupt drug withdrawal - opiate withdrawal syndrome
Type F - Failure of therapy
DoTS - ADRs classification
Dose relatedness
Timing
Patient susceptibility
Risk factors for ADRs
Patient risk - F>M, Elderly and neonates, polypharmacy, genetic predisposition, hypersensitivity/allergy, hepatic/renal impairment
Drug risk - Low therapeutic index, a steep dose-response curve
Prescriber risks
Causes of ADRs
Pharmaceutical variation
Receptor abnormality - malignant hyperthermia with general anesthetics
Abnormal biological system unmasked by drug - primaquine induced haemolysis
Abnormalities in drug metabolism
Immunological
Drug-induced interaction
Multifactorial - many reasons
Type A - Augmented, predictable
Extension of primary effects - bradycardia and propanolol
Type B - Bizzare, not predictable
Allergy
Hypersensitivity
Idiosyncrasy
Inherent abnormal response to a drug
Rare but serious
Types of allergic reaction
Type 1 - Immediate anaphylactic - IgE
Type 2 - Cytoxic antibody - IgG, IgM
Type 3
Type 4 - Delayed hypersensitivty - contact dermatitis
Type C - Continuous
Steroids and osteoporosis
Analgesic nephropathy
Steroids and Iatrogenic Cushing’s syndrome
Colonic dysfunction due to laxatives
Type D - Delayed
Teratogensis - drugs taken in the first trimester
Type E - Ending of drug use
Withdrawal
ADR suspicion
New drug
Dosage increase
Drug is stopped
Most commons drugs with ADRs
Antibiotics Anti-neoplastics NSAIDs CNS drugs Hypoglycaemics Cardiovascular drugs
Most common systems affected
GI Renal Haemmorhagic Endocrine Dermatological
Common ADRs
Confusion Nausea Balance problems Diarrhea Constipation Hypotension
Black triangle indicates a medicine
Undergoing additional monitoring
Serious reactions
Fatal
Life-threatening
Disabling
Results in hospitalisation or prolongs it
Allergic reactions to drugs
Interaction of drug/metabolite/non-drug element with patient and disease
Subsequent re-exposure
Exposure may not be medical - penicillin in dairy products`
Intolerance is not same as
Allergy
Drug hypersensitivity
Immediate - anaphylaxis
Delayed - rahes, hepatitis, cytopenis
Anaphylaxis can be
Immunological
Non-immunological
Anaphylaxis is mediated by
IgE
Type 1 hypersesnivity
Acute anaphylaxis
Prior exposure to antigen/drug
IgE antibodies formed and attach to agents and activate the release of histamine, prostaglandins etc
Anaphyaxlsis
Rapid onset Vasodilaiton Increased vascular permability Bronchoconstriciton Urticaria Angeo-oedema
Type 2 reactions
Antibody-dependent cytotoxicity
Drug or metabolite combines with protein
Type 3 reactions
Antigen-antibody complexes and activate complement
Vasculitis
Type 4 reactions
Lymphocyte mediated
Contact dermatitis
Stevens-Johnson syndrome
Non-immune anaphylaxis
Due to direct mast cell dragranulation
No prior exposure
Anaphylaxis main features
Exposure to the drug, immediate rapid onset
Rash
Swelling (lips, face, oedema, central cyanosis)
Wheeze/SOB
Hypotension (anaphylactic shock)
Cardiac arrest
Shock
Lack of body organ perfusion
Leads to loss of consciousness
Management of anaphylaxis
ABC Stop drug if infusion Adrenaline IM/Epipen High flow Oxygen IV fluids IV Antihistamine IV Hydrocortisone IV Adrenaline for Anaphylactic shock
Adrenaline
Vasoconstriction
Stimulation of B1 adrenoreceptors
Reduces oedema and bronchoconstriction
Risk factors for hypersensitivity
Medicine factors - proteins or macromolecules
Host factors - F>M, HIV, Pred drug reaction, uncontrolled asthma
ABC
ATP Binding Cassette
Carrier mediated transport
SLC
Soluble carrier
OAT1 is an example - organic anion transporter, found in kidney and secretes penicillin and uric acid
Probenecid blocks it leading to uric acid excretion
Pinocytosis
Carrier mediated entry into the cytoplasm
Amphotericin
Antifungal
Drug absorption in gut
Drug needs to be lipid-soluble to be absorbed into gut
Drug formulation
Some formulated to dissolve slowly (modified release) or have an enteric coating that is resistant to stomach acidity - Aspirin has an EC
First pass metabolism - Barriers
Intestinal lumen
Intestinal wall
Liver
Lungs
Intestinal lumen
Digestive enzymes
Intestinal wall
Cellular enzymes - MAO
Efflux transporters - P-gp which limits absorption by transporting drug back into gut lumen
Liver
Major site of drug metabolism
Transcutaenous
Transdermal patches - Fentanyl patches
Thiopental
Rapid anaesthetic because of initial high brain conc, but is short-lived as continued muscle uptake lowers blood conc and indirectly the brain conc
Protein binding
Commonest reversible binding occurs with plasma protein albumin
Lipid soluble drugs
Pass easily through BBB
CYP450
Membrane bound isoenzyme
Present in smooth endoplasmic reticulum
Largely in livet tissue
Cimetidine and grapefruit induce/inhibit CYP450
Smoking and alcohol increase drug metabolism rapidly which can lead to consequences
Phase 1 reaction
Breaking drug down
Introduction of a functional group
Phase 2 reaction
Building drug up with functional active chemical groups (such as methyl group)
Excretion
Fluids - urine, bile, sweat, breast milk
Solids - faeces, hair
Gases - expired air (volatiles)
Total urine excretion determined by
Glomerular filtration
Tubular secretion
Reabsorption
Ethanol enzyme system
Alcohol dehydrogenase
Ciprofloxacin
UTI drug
Lipid vs water-soluble drugs
Lipid soluble faster than water-soluble drugs
Opiates
Analgesia
Codeine, tramadol
Depressants
Sedation
Benzodiazepines, gabapentinoids, alcohol
Stimulants
Increase alertness
Amphetamines, cocaine, caffeine, ecstasy/MDMA
Cannabinoids
Relaxation, euphoria
Cannabis, spice
Hallucinogens
Altered sensory perceptions
LSD, magic mushrooms
Anaesthetic
Anaesthesia, sedative
Ketamine, NOX
New psychoactive substances
Legal high
Tend to be used in clubs
Substance use disorder (addiction)
Compulsive use of a substance despite harmful consequences
Alcohol units guidelines
14 units per week spread over 3 days or more
Alcohol specific deaths by condtition
Alcoholic liver disease
Alcoholic cardiomyopathy
Alcohol induced acute pancreatitis
Alcohol withdrawal
Tremors Agitation Tachycardia Hptn Seizures Hallucination - visual/tactile
Alcohol and pregnancy
Foetal alcohol syndrome - Pre/postnatal growth retardation, Craniofacial abnormalities
Psychosocial effects of excessive alcohol consumption
Interpersonal relationships - violence, rape, depression/anxiety
Work problems
Poverty
Driving incidents/offences
Alcohol-use disorders - Primary prevention
Pricing - Make less affordable (MUP - minimum unit pricing)
Availability - Licensing
Marketing - Limit exposure to young children
Campaigns - Drinkaware
Alcohol-use disorders - Screening
Clinical interview as part of routine exam in patients who are pregnant, smoking, health problems that are likely alcohol-induced
FAST - Fast alcohol screening test