*Analgesics Flashcards
5 Cardinal signs of inflammation
- Heat
- increased vascular perfusion delivers core blood to the affected region
to facilitate optimal temperatures for enzymatic activity
- increased vascular perfusion delivers core blood to the affected region
- Red
- local vasodilation facilitates swelling and immune cell infiltration to
facilitate destruction or isolation of the pathogen and remove cell debris
- local vasodilation facilitates swelling and immune cell infiltration to
- Loss of function
- local pain reduces mobility of the affected body area which
limits movements that could aggravate preparative steps in tissue repair
- local pain reduces mobility of the affected body area which
- Pain
- physical swelling and released mediators from immune cells stimulate
pain fibers
- physical swelling and released mediators from immune cells stimulate
- Swelling
- exudation of plasma and proteins from locally dilated capillaries
isolates the wound and pathogen and facilitates immune cell access
- exudation of plasma and proteins from locally dilated capillaries
Inflammation
- NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) is a ”rapid acting” (preformed), first responder transcription factor residing in the cytoplasm of all cells
- In responsive to a variety of hyperosmolar tears(often associated with dry eye), harmful stimuli, and
cytokines, NF-κB activation begins with the phosphorylation and
subsequent degradation of its inhibitor proteins - Once activated, NF-κB initiates transcription of genes involved in
inflammation, T-cell activation; innate and adaptive immune responses,
cell survival responses, and cellular proliferation - Defective NF-κB activity is linked to cancer, inflammation, AI diseases,
septic shock, and viral infection - MMP-9, an inducible(has to be synthesized first) matrix metalloproteinase, is another key player in
the inflammatory response
Which autonomic responses are associated with pain?
(SNS, PNS shut down):
- Tachycardia
- Systemic hypertension
- Tachypnea
- Diaphoresis (cold sweat)
- Pallor
- Nausea
Therapeutic relief mechanisms for treating pain
- Peripheral(directly at the source, i.e. hand),:
- block pain mediators,
- receptor sensitization
- afferent neuronal discharge
- Central:
- block pain receptors in the CNS
Once activated NF-KB initiates transcription of genes involved in…
- Inflammation
- T-cell activation
- Inate and adaptive immune responses
- Cell survival responses
- Cell proliferation
Defective NF-KB is linked to
- Cancer
- Septic shock
- Inflammation
- Viral infection
- Auto immune diseases
Inflammatory pain mediators
- Nociception - reception/sensation of harm/pain
- Bradykinin, NE, and histamine stimulate pain fibers (likely a combination)
- Bradykinin - RAAS → vasodilation, also produces pain
- NE - SNS → pain linked to NE
- Histamine - key molecule in allergic (type 1 sensitivity) reactions
- Allodynia (an exaggerated pain response) can result when pain fibers are (hyper)sensitized by low pH, bradykinin, prostaglandins (PGs), leukotrienes (LTs), and Substance P
- Inflammation leads to ↓ pH
- Clinical application: eye → painful to touch
- PGE2 & PGI2 (prostaglandins) promote pain and inflammation
- Other Mediators:
- Cytokines (interleukins, interferons, tumor necrosis factors, growth factors and chemokines)
- Nitric Oxide (for good and bad → inflammation-induced pain → inflammation leads to iNOS [produces lots of NO, that now stimulate pain fibers])
- Platelet Activating Factor (PAF)
Define allodynia
- An exaggerated pain response can result when pain fibers are sensitized by low pH, bradykinin,
prostaglandins leukotrienes, and Substance P- PGE2 & PGI2 promote pain and inflammation
Inflammation pathway
Leukotriene type 4 and Prostaglandin type 2 = pro inflammation
(even numbers = bad)
Leukotriene type 5 and Prostaglandin type 3 = anti-inflam
(Odd numbers = good)
PGI2 and TXA2 are physiologic antagonists
COX 1 vs COX 2
COX 1
- Constitutive (housekeeping, always active) enzyme; predominantly
involved in PG & TXA2 production- GI mucosa, vasculature, platelets, macrophages, kidneys
COX 2
- Constitutive(pre-produced, ready to go) enzyme in the kidney
- Inducible enzyme; predominantly involved in PG production
- Generates pro-inflammatory PGs and O2 radicals
- Creates pain and pyresis from inflammatory focus
Leukotrienes LTB4 , LTC4 and LTD4
LTB4
- chemotactic by activating phagocytes and
promoting neutrophil adhesion - key role in signalling to immune cells
LTC4 and LTD4
- enhance histamine effects(itch,pain), bronchoconstrict,
and constrict coronary arteries and dilate vessels in
regions of inflammation
PG’s actions on kidney
PGE2 & PGI2 promote maintenance of renal blood flow by
stimulating renin release (ontributes to elevation in BP)
PG’s an TXA2 actions on vasculature
- PGE2 causes edema (swelling) and vasodilation (redness)
- PGI2 produces vasodilation
- TXA2 (Thromboxane A2) is a vasoconstrictor
PGI 2 and TXA2 physiologic antagonists
PG’s and TXA2 actions on platelets
- TXA2 promotes platelet aggregation
- PGI2 inhibits platelets
PG’s effect on GI tract
- PGE1 & PGE2: production of cytoprotective GI mucous
• PGI2 (Prostacyclin): decrease GI acid secretion
PAFeffect on connective tissue
PAF (Platelet Activating Factor) activates matrix
metalloproteinases
PGE2 effect on CNS
PGE2 causes fever through the hypothalamus
PGF2A effects on reproduction
PGF2a causes suppression of spermatogenesis & uterine
contraction
Endogenous analgesics
-
Endorphins
- Induced by Tricyclic Antidepressants (TCADs)
- Elevated in Cushing’s syndrome
-
Serotonin
- A mood regulator; linked to depression and arousal
- A short-term analgesic; counteracts Substance P
- Induced by paracetamol
- Reuptake is inhibited by Tramadol, selective serotonin
reuptake inhibitors (SSRIs), and selective norepinephrine
serotonin reuptake inhibitors (SNRIs)
** Acetylsalicylic Acid (Aspirin)
Dosing for
- Anti-platelet activity
- Analgesia
- Anti-pyretic (fever)
- Anti-inflammatory
- Anti-platelet - 80-160 mg
• Irreversible inhibition of COX-1 (TXA2) for life of platelets - Analgesia - 160-325 mg
• Low intensity pain: central < peripheral
• t1⁄2 2-3 hrs - Anti-pyretic - 160-325 mg
• t1⁄2 2-3 hrs - Anti-inflammatory - 325-650 mg
• t1⁄2 ~10 hrs
Mechanism of action of ASA (aspirin/acetylsalilicylic acid)
Irreversibly, non-selectively inhibits COX, reducing PG and
TXA2 synthesis
Adverse reactions of ASA (Aspirin/acetylsalicylic acid)
- Common:
- bleeding time doubles, headache
- Serious:
- Hypersensitivity: angioedema
- Special: Reye’s Syndrome (35% mortality)
Topical Ophthalmic Drug Interactions
• None
Contraindications
• Hemorrhagic disorders
• Pregnancy, esp 3rd trimester
Ocular: Corneal denervation, dry eye
What medication is associated with corneal denervation?
Aspirin / acetylsalicylic acid
What is Reye’s syndrome and which drug can cause it
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Reye’s syndrome
Adverse reaction in children taking ASA to reduce fever
in viral infections (eg. chicken pox or influenza)
• GI disturbances
• Liver degeneration
• Encephalopathy
35% mortality
Indications of Celecoxib (COX 2 inhibitor)
Osteoarthritis:
• Rheumatoid arthritis:
• Ankylosing Spondylitis:
• Dysmenorrhea:
• Acute Pain:
Mechanism of action of Celecoxib
Selectively inhibits COX-2 and reduces PG synthesis
*Sulpha based drug*
Adverse reactions of Celecoxib (selective COX 2 inhibitor)
- Common: headache
- GIT: Bleed, ulceration/perforation
- Black Box: Stroke, CHF, MI
CHF- congestive heart failure
MI - myocardial infarction
Topical Ophthalmic Drug Interactions of Celecoxib (COX2 inhibitor)
- Bromfenac, diclofenac, flurbiprofen, ketorolac, nepafenac: additive hemorrhage risk
- • Naphazoline, tetrahydrozyline, phenylephrine: additive hypertensive risk
- Cautions
- Hypertension, smokers
Indications of Acetaminophen (Paracetamol)
Pain and fever
Mechanism of action of Acetaminophen (Paracetamol)
- Acts by inhibiting COX and enhancing 5-HT release (attenuates pain mediator generation)
- Regulates body temperature by acting centrally at the hypothalamus; PG synthetase inhibition
Adverse effects of acetaminiphen (paracetamol)
Common: headache
Topical Ophthalmic Drug Interactions
• None
Contraindications/Cautions
• No applicable ophthalmic conditions or findings