Non-Opioid Analgesics Flashcards
Define pain
Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
What are the two types of physiological pain?
Nociceptive pain and inflammatory pain
What is nociceptive pain?
Nociceptive pain is a response to a painful (nociceptive) stimulus, often followed by a protective response E.g. autonmomic withdrawal reflex.
What is inflammatory pain?
Inflammatory mediators lead to pain hypersensitivity - adaptive, low threshold pain.
What is the adaptive purpose of inflamamtory pain?
The tenderness that accompanies inflammatory pain follows promotes rest and repair.
Describe the process of prostaglandin synthesis from essential fatty acids
- Essential fatty acids converted to membrane phospholipids
- Membrane phospholipids converted to arachidonic acid by phosphplipase A2
- Arachidonic acid converted to prostaglandin by cyclo-oxygenase (COX)
What role do prostaglandins play in inflamamtion?
Prostaglandins create areas of swelling, vasodilating and pain at sites of injury.
How do NSAIDs function?
NSAIDs block the formation of prostaglandins by inhibiting cyclo-oxygenase (COX) enzyme.
What are the four groups of adverse effects encountered with NSAID use?
- GI - irritability, bleeding
- Renal - if renal impairment
- Platelet - increased risk of bleeding (non-selective NSAIDs)
- Respiratory - NSAID induced astham in 15% asthmatics
What adverse GI effects occur with NSAID use?
Irritability, bleeding, gastric/duodenal ulceration
What adverse renal effects can occur with NSAID use?
NSAIDs are generally very well tolerated if renal function is normal.
If impaired, can cause fluid retention, oedema and hypertension.
What are the possible platelet related adverse effects of NSAIDs
Non-selective NSAIDs carry an increased risk of bleeding.
Selective COX-2 inhibitors carry an increased risk of thrombotic events.
What are the adverse effects that can be seen with NSAID use in asthmatics?
NSAID use can trigger asthma in 15% of asthmatics.
Three broad effects of NSAIDs?
- Anti-inflammatory
- Anti-pyretic
- Analgesic
Factor that influence choice of NSAID administration?
Route of administration (IM, IV, oral)
Duration of treatment
Patient factors (risk to benefit with contraindications)
Four groups of non-selective NSAIDs with an example?
- Salicylates - Aspirin
- Propionic acids - Ibuprofen
- Phenylacetic acids - Diclofenac
- Oxicams - Meloxicam
Name the common intramuscular NSAID and its group.
Ketorolac - A phenylacetic acid.
How are COX-2 selective NSAIDs named, giving an example.
-coxib
E.g. celecoxib.
What are the advantages and disadvantages of COX-2 selective inhibitors?
Advantages:
- Lower GI adverse events
- Reduced risk of intraoperative bleeding
- Does NOT cause bronchospasm in asthmatics
Disadvantages
- Increased risk of MI and strokes with long term use - thrombotic events
What is the main use for aspirin and how does it function?
Aspirin is largely used for anti-platelet effects, in the prevention of MI and stroke.
Aspirin selectively inhibits COX-1 (platelet cyclo-oxygenase), inhibiting thromboxane A2 formation. Thromboxane A2 is responsible for platelet aggregation and clotting.
Adverse effects of aspirin at therapeutic dose?
- GI effects, similar to NSAIDs
- Bleeding risk
- Reyes Syndrome - hepatic failure, encephalopathy in children <12 years
- Long term - hepatic/renal impairment.
Adverse effects of aspirin at supra-therapeutic doses?
- Mortality
- Respiratory alkalosis
- Metabolic acidosis
- Renal papillary necrosis
What are the analgesic, anti-pyretic and anti-inflammatory properties of paracetamol?
Paracetamol has an analgesic and anti-pyretic effect, but NO anti-inflammatory effects.
Why does paracetamol have limited adverse effects?
Inactive at other sites, such as kidney, GI
- No renal impairment (safe to use in kidney disease)
- No ulcer risk in GI
