Modern Arsenal of Pain Control Flashcards
What do norepinephrine and serotonin do?
Inhibit pain signals from reaching the higher levels of brain
How do tricyclic antidepressants (TCAs) work?
Increases serotonin and or norepinephrine in the synapse by inhibiting reuptake
May have anticholinergic effects
How long does it take for TCAs to begin working?
1-3 weeks for pain control so used for chronic pain
What are some examples of TCAs?
Notriptyline and Amitriptyline
What are TCAs more effective for treatment of?
Diabetic neuropathy, moreso than other antidepressants
How do selective serotonin reuptake inhibitors (SSRIs) work?
Specific inhibitors of serotonin reuptake
What are some examples of SSRIs?
Paroxetine (Paxil), Fluoxetine (Prozac), Sertraline (Zoloft)
What are some side effects of SSRIs?
Suicidality, impaired platelet aggregation, CNS depression, QT prolongation, serotonin syndrome, hyponatremia, sexual dysfunction
How do serotonin and norepinephrine reuptake inhibitors (SNRIs) work?
Potent inhibitor of neuronal serotonin and norepinephrine reuptake and weak dopamine reuptake
What are some side effects of SNRIs?
Suicidality, serotonin syndrome, rest are same as SSRIs
What are some examples of SNRIs?
Venlafaxine (effexor), duloxetine (cymbalta)
What is venlafaxine used for?
Neuropathic pain, diabetic neuropathy
Onset 1-2 weeks, max 6 weeks
What are some adverse reactions from venlafaxine?
Nausea, dizziness, drowsiness, hyperhidrosis, hypertension
What is duloxetine used for?
Diabetic neuropathy, fibromyalgia, chronic MSK pain
60-120 mg daily
What are some adverse reactions of duloxetine?
Sedation, nausea, constipation, ataxia, dry mouth
How do alpha adrenergic agonist work?
Stimulates alpha adrenoreceptors in the brainstem, activating inhibitory neuron, reducing the sympathetic outflow of CNS (prevents pain signal transmission)
What are some examples of alpha adrenergic agonists?
Clonidine (last line of treatment)
Tizanidine
What is clonidine used for?
Neuropathic pain that is not responding to other treatment
Unlabelled: Heroin or nicotine withdrawal, dysmenorrhea, menopausal vasomotor symptoms, migraine prophylaxis
What are some adverse effects of clonidine?
Bradycardia, CNS and respiratory depression, hypotension
What is tizanidine used for?
Tension-type headache, back pain, neuropathic pain and myofascial pains
Less likely to cause hypotension than clonidine
What is peripheral sensitivity?
Neuropathic pain triggered by spontaneous peripheral nerve activity mediated by sodium channels caused by local tissue injury, ischemia releasing inflammatory factors, increasing Na channels
What medications are used for peripheral sensitivity?
Carbamazepine, tricyclic antidepressants, topiramate, lidocaine
What does carbamazepine do?
An anticonvulsant that limits the influx of sodium ions across the cell membrane
What is carbamazepine used for?
Trigeminal or glossopharyngeal neuralgia and neuropathic pain
Monitor drug levels (reach a steady state in 2-5 days)
What does topiramate do?
An anticonvulsant that limits the influx of sodium ions and antagonizes glutamate receptors
What are some adverse reactions of topiramate?
Dizziness, ataxia, somnolence, psychomotor slowing, paresthesia, weight loss
What should be monitored while on topiramate?
Electrolytes and kidney function
How does lidocaine work?
Topical application reduces discharge of small afferent nerve fibres by blocking voltage-gated sodium channels (decrease membrane permeability)
Gel or patch (will only work in area applied, max 3 patches to area every 24 hours)
What is lidocaine used for?
Post-herpetic neuralgia or peripheral neuropathies or other etiologies
What are some side effects of lidocaine?
Arrythmias, seizures, coma, respiratory depression or death
Patch: Erythema, swelling, burning or discomfort of the application site
How does central sensitivity occur (GABA, Ca)?
Occurs in dorsal horn of the spinal cord with the release of excitatory neurotransmitters (glutamate, substance P) and increased calcium transport (spontaneous impulses)
Which medications decrease calcium channel activity?
Gabapentin and Pregablin
How do gabapentin and pregablin work?
Modulate voltage gated Ca channels by binding alpha2-delta subunit of presynaptic neurons to regulate excitatory neurotransmitters
What is gabapentin used for?
Diabetic neuropathy and neuropathic pain
What are the adverse reactions of gabapentin and pregablin?
Somnolence, dizziness, peripheral edema
What is pregablin used for?
Neuropathic pain/diabetic neuropathy, spinal cord injury neuropathic pain
Which medications are NMDA antagonists (decrease nerve impulse)?
Ketamine, dextromethorphan, methadone
How does ketamine work?
Decreases central sensitization and modulation by lowering the threshold for nerve transduction and reduces the effects of substance P
Also is a dissociative agent that targets the opioid receptor, Na and K channels to reduce pain
What are some adverse reactions to ketamine?
Local skin reactions
How does dextromethorphan work?
Low affinity uncompetitive NMDA antagonist (high doses needed), also binds opioid receptors
Very short half-life
What some side effects of dexomethorphan?
Serotonin syndrome (if in combination with other antidepressants), rash, nausea, drowsiness, constipation/diarrhea, confusion, nervousness, closed-eye hallucinations
How does methadone work?
Mu and delta opioid agonist that also blocks the NMDA receptor and inhibits the reuptake of norepinephrine
What makes methadone better than morphine?
1 mg=10 mg morphine
Less need for opioid escalation, no active metabolites (less side effects), highly lipophilic (high bioavailability)
What are some side effects of methadone?
CNS and respiratory depression, QT prolongation, constipation, nausea and vomiting, dizziness and disorientation
