Applied Pharmacology Flashcards
What is analgesic?
Drug that relieves or reduces pain
Control of symptoms and improvement of patients quality of life.
What does the NSAIDs mean?
Non-steroid anti-inflammatory drug
What is the arachidonic acid cascade?
Mechanism explaining NSAID action (include side effects)
Main action is to block COX enumerated
- Arachidonic acid -fatty deposit
- Cyclooxyrgenase (COX) act on arachidonic acid
- convert AA to intermediates NSAID - competitive inhibition of COX enzymes stop cascade
- Other cell/tissue specific enzymes – convert intermediates to prostanoids
- Prostanoids – product (examples prostaglandins (activate the nociceptive receptors) and thromboxane)
What does NSAID do in the arachidonic acid cascade?
- intermediate NSAID
- competitive inhibition of COX enzymes
- attach to binding sites
- stop cascade
What are the different types of COX enzymes?
COX 1
COX 2
COX 3
What does COX 1 enzyme do?
COX 1 – most tissue/ cell – mainly endoplasmic reticulum – gastric protection, blood flow and platelet aggregation.
What does COX 2 enzyme do?
COX 2 – mast cells, fibroblasts, macrophages 0 endothelial cells – more in nuclear membrane – inflammation, pain and fever
What does the COX 3 enzyme do?
COX 3 – Mainly found in CNS – animal models – poor understanding – may not be active in humans
Explain binding selectivity of NSAIDs?
Different NSAIDs more actively attach to the different COX enzymes
Ketoprofen – more COX 1 selective
Celecoxib – more COX 2 selective
Aspirin and Fenoprofen – equally selective
NSAID mechanism of action - 4 main therapeutic effects
- Anti-inflammatory
- Analgesic (reduce pain)
- Antipyretic (prevent or reduce a fever)
- Platelet aggregation
Whats Special about aspirin binding to arachidonic acid binding site?
Irreversible binding to arachidonic acid
Other NSAIDs are usually reversible
What are the anti-inflammatory effects of NSAIDs?
-Inhibit COX-2 derives prostaglandins (powerful vasodilators)
- reduced vasodilations
- reduced oedema
- reduced swelling
- reduced redness
- reduced neurogenic inflammation
Promote release of other vasodilators (substance P and histamine)
What is the analgesic effects of NSAIDs?
- Inhibit COX-2 derived prostaglandins
- Reduced peripheral and central sensitisation of free nerve endings
So – reduce prostaglandin production, reduced transmitter release, reduced 2nd order neuron sensitivity
What are the antipyretic effects of NSAIDs?
-Pyrogens – stimulate PGE2 in hypothalamus
- PGE2 – inhibits temperature sensitive neurons
- NSAIDS – reduce PGE2 production by binding to COX-2
What are the platelet aggregation effects of NSAIDs?
-Good COX-1 selectivity – covalent binding (non reversible as covalent
binding)
- COX-1 inhibition reduces thromboxane A2 production (a prostanoids end of Arachidonic acid cascade)
- Platelet never recover =ability to aggregate
- New platelet production required
State the side effects of NSAIDs
- Gastrointestinal prostaglandins promote production of alkali mucus – NSAID blocks prostaglandin production, aspirin induced gastritis and alteration side effects)
- Respiratory
- Renal
Liver
What are the effects of COX-2 enzyme?
More prevalent
- Inflammation, pain and fever
Less prevalent
Gastric protection, blood flow and platelet aggregation
Whats pros and cons of COX-2 selective NSAIDs?
pros
- Fewer gastric complications
- Reduced effects on platelet aggregation
cons
- Evidence of reduced analgesia
- Increased thrombin/ cardiovascular risks associated
Explain the Respiratory side effect of NSAID?
- Aspirin induced asthma
- When tissue injury and arachidonic acid produced lipoxygenase enzymes also act to produce leukotriene which is a bronchi constrictor
Whats the renal side effects of NSAIDs?
- Block prostaglandin production reduces renal filtration and sodium retention.
- Preventing the vasodilation which promotes glomerluar filtration – reduced filtration
What is the liver damaged caused by NSAIDs?
- Low incidence – multiple mechanisms postulated
1.retention of bile (cholestasis)
2. Mitochondrial damage
3. inhibition of prostaglandin E2 production
4. Reactive metabolites
Whats the effect of paracetamol?
-Pain relief/ antipyretic effect
- non-opioid (Not really an NSAID)
- poor peripheral COX1/2 inhibition
- Target COX2 in CNS (maybe also COX3)
- Does not inhibit platelet aggregation
- Doesn’t damage gut mucosa
Whats the pros of paracetamol?
Does not inhibit platelet aggregation
- Doesn’t damage gut mucosa
Whats the pharmacokinetics of paracetamol?
Paracetamol effected on my cytochrome
Cytochrome P450 – NAPQ1 (very toxic to liver)
But almost immediately effected on by Glutathione (limited amount of production in body) to make Glutathione conjugate
How is paracetamol overdose easy?
Very toxic NAPQ1
Converted by glutathione which is limitedly produced in a day so must not exceed the supply other liver damage and down to DNA damage.
What is a mild opioid?
Compound resembling opium
Mainly work by weakly activating opioid receptors and have lower efficacy at the receptors
- Bind to specific opioid receptors
- Mimic action of endogenous peptide neurotransmitters
What are the three categories of opioids?
- Natural – occur biosphere
- Semisynthetic – chemical derivative
- Synthetic – noval man-made molecular structure
State the three different opioid receptors
Delta and mui receptors – supraspinal – spinal and peripheral – euphoric feelings
Kappa receptor – spinal