Analgesics Flashcards
(36 cards)
Aspirin MoA?
Non-competitive, irreversible inhibition of COX1 and COX2, preventing synthesis of prostaglandins.
Indications for aspirin?
- Inhibition of platelet aggregation
- Mild-mod pain
- Fever / Rheumatic fever
- Migraine
- RA
- Kawasaki disease
When should precautions be taken with aspirin?
- Allergic rxn to aspirin / NSAID
- Heart failure / HTN
- Asthma
- Gout
- G6PD deficiency
- PUD
Common adverse effects of aspirin?
- N/V
- Headache / dizziness / tinnitus
- GI ulceration / bleeding
Adult dosage of aspirin for pain?
300 - 900 mg every 4-6h.
What is nociception?
Detection, transduction and transmission of noxious stimuli.
What are the equilavent dosages of opioids? (based on 10mg morphine)
- 10mg morphine
- 100mg codeine PO
- 5mg oxycodone
- 2mg hydromorphone
In which pts should NSAIDs be used with caution?
- Asthma
- Coagulopathy
- GI ulcer
- Renal insufficiency
- Pregnancy, 3rd trimester
What are the side effects of opioids?
CHARMEN
- Constipation
- Histamine release (itching / urticaria / bronchoconstriction => morphine only)
- Addiction / dependence
- Respiratory depression
- Miosis
- Euphoria
- N/V
What should be considered when prescribing opioids?
- Breakthrough dose
- Anti-emetics
- Laxative
What is the mechanism of action of paracetamol?
?COX 2 inhibitor / modulation of endogenous cannabinoid system
What is max dose of paracetamol?
4g / 24h
Side effects of paracetamol?
- Hepatotoxicity
- HTN risk in women
- Nephrotoxicity
- Mild coagulopathy
MoA NSAIDs?
Non-selevtive COX1 and COX2 inhibition reducing proinflammatory cytokine synthesis.
Side effects of NSAIDs?
- GI ulceration/bleeding
- Decreased renal perfusion
- Photosensitivity
- Premature closure of ductus arteriosus in pregnancy
What are the oral opioids?
- Codeine
- Oxycodone
- Morphine
- Hydromorphone
Parenteral opioids?
Morphine, hydromorphone, fentanyl.
MoA of opioids?
- Dampens nociceptive transmission between 1st and 2nd order neurons in the dorsal horns
- Activates ascending modulatory pathways releasing inhibitory neurotransmitters
- Inhibits peripheral inflammatory response and hyperalgesia
- Affects mood and anxiety - alleviates affective component of perceived pain
What is the analgesic ceiling?
The maximum effect (pain relief) that can be induced in a tissue by a given drug, regardless of increasing doses.
Which analgesics are subject to the ceiling effect?
Paracetamol, NSAIDs, codeine. NOT opioids (except codeine).
How does opioid overdose primarily present?
CNS (e.g. respiratory depression). Manage ABCs
MoA opioid antagonists?
Competitively inhibit opioid receptors, predominately u (mu) receptors.
Duration of naloxone action?
T1/2 relatively short (60mins). May wear off with return of narcotic effect.
Duration of naltrexone action?
Longer T1/2 than naloxone ==> 10h duration.
Less likely to have return of opioid effect
