Lecture 9: Pain Pharmacology Flashcards
What is the key difference between an anesthetic and an analgesic?
Anesthetics involve depressing all CNS characteristics, aka loss of all sensory modalities. Usually accompanied by LOC.
Analgesics are pain only, no LOC.
What is the gate-control theory?
Non-painful stimuli shut the gate to painful stimuli, preventing pain sensation from traveling to the CNS.
What do we use non-opioid medications for?
Adjuvants
First-line therapy for pain
Anesthesia
What are the side effects of corticosteroids?
Adrenal suppression
Appetite stimulation/weight gain
Cataracts formation
Impaired glucose metabolism
Edema
CHF
Osteoporosis
PUD
Bleeding
Mood changes
Steroid Psychosis
Joint degradation/atrophy at injection site with repeated injections.
What is the mechanism of action of corticosteroids?
Inhibition of phospholipase A2, which decreases the production of arachidonic acid and the inflammatory mediators.
What are the two pathways NSAIDs target?
COX-1
COX-2
What is the MoA of an NSAID?
Inhibition of the COX pathway. Subsequently inhibits prostaglandin formation.
Inhibits urate crystal phagocytosis (gout)
What does COX-1 inhibition commonly cause?
GI issues
Some prostaglandins are protective to mucosa which inhibit acid erosion
What does COX-2 inhibition commonly cause?
Decreases prostaglandins which therefore decrease inflammation, pain, fever
ALSO causes platelet aggregation and vasoconstriction, which is why celebrex has a cardiac black box warning.
What is the PK of an NSAID?
Low pH causes absorption by intestinal and gastric mucosa.
Binds to albumin
Conjugated to inactive metabolites, renal excretion.
What lab test should I order before giving someone NSAIDs?
Renal function test, to check GFR.
What are the other names for tylenol?
Acetaminophen/Paracetamol.
Scientific name: N-acetyl-p-aminophenol (APAP)
What is the MoA for Tylenol?
It is a selective COX inhibitor that generally targets COX-2.
Metabolites of APAP bind to TRPA-1 receptors, suppressing signal transduction of dorsal horn.
Why is tylenol an antipyretic?
COX enzyme reduction decreases formation for prostaglandin H2, which decreases E2 in hypothalamus (responsible for thermoregulation).
What is the max dose of tylenol in adults?
3000mg/day
What kind of toxicity does excessive tylenol cause?
Hepatotoxicity
When is NAPQI formed?
APAP metabolite formed after CYP metabolism.
Hepatotoxic!
What two conditions can cause hepatotoxicity with tylenol?
High dosages and/or low glutathione, which is caused by excessive ETOH.
What kind of lab test should I order prior to tylenol use?
Liver function tests.
What are other non-opioid medications?
Lidocaine patch/cream
Antispasmodics
Compounding pharmacy topicals
Membrane stabilizers
How do opioids work in general?
Alkaloid opiates mimic the action of endogenous endorphins (enkephalins) that are normally produced for analgesia by attaching to opioid receptors.
What kind of receptor interaction are opioids?
Ligands binding to G-Protein coupled receptors.
What are the 3 opioid receptor subtypes?
Mu (u)
Kappa (k)
Delta
What is the main opioid receptor subtype?
Mu: responsible for analgesia, respiratory depression, GI SE, sedation, and pruritis.