Pharm - MSK Flashcards
(26 cards)
Nonopioid Analgesics
- acetaminophen
- asa and nonacetylated salicylates
- NSAIDS
Adjuvant agents
- corticosteroids
- muscle relaxants
Acute Pain
- Occurs as a result of injury
– Self-limited
– Adaptive
Chronic Pain
- Pathologic
- Maladaptive
- Can be intermittent, persistent or both
TX: general approach
- identify source of pain
- assess level of pain
- choose therapy based on pain severity/type
- use least potent oral analgesic that relieves pain with fewest AE
- titrate dose to control pain
- use drugs on fixed schedule rather than PRN
- assess effectiveness and AE regularly
- avoid excessive sedation
- change route of admin if necessary
Analgesic
- effective only against low-to-mod pain intensity (dental pain).
- Chronic post op pain or pain from inflammation
Antipyretic
-reduce fever but not the circadian variation in temp or the rise in response to exercise/ambient temp
Anti-inflammator
NSAIDs play a key role int he tx of MSK disorders (RA and osteoarthritis).
NSAIDS only provide symptomatic relief from disease assoc pain and inflammation and do no prevent disease progression
Acetaminophen
- analgesic and antipyretic
- inhibits CNS prostaglandin synthesis (COX-3)
- hepatotox
- chronic doses should be less than 4g/day
- reduce to 2-3g/day if: renal impairment, hepatic disease or excessive alcohol use
- increase warfarin effect at doses above 2g/day
ASA
- analgesic, antipyretic and anti-inflamm
- inhibits COX 1 and 2
- very effective for pain from prostaglandins
- irreversibly inhibits platelets
- AE: GI irritation, hypersensitivity
Nonacetylated Salicylates
- Choline magnesium salicylate, sodium salicylate, diflunisal
- similar effects as ASA
- Less GI irritation
- reversible platelet inhibition
NSAIDs
-analgesic, antipyretic, and anti-inflamm
-inhibit both COX 1 and 2
-2-3 weeks of therapy is considered sufficient trial
-classes are divided based on chem structure and differ in dose and drug interactions
-selective COX 2 inhibitors to minimize GI tox: celecoxib but may increase risk of CV events
AE: GI, renal insufficiency, CV, drug interactions
Corticosteroids
Adjuvant therapy
- tx for pts unable to take NSAIDs
- AE: fluid retention, wt. gain, hperglycemia, CNS stimulation
Muscle relaxants
Adjuvant therapy
-spasmolytics
-used in combo w/ NSAIDs for pain assoc w/ muscle spasms
-decrease spasms/stiffness in acute or chronic conditions
-AGENTs: baclofen, metaxalone, methocarbmol, carisoprodol, cyclobenzaprine
AE: sedation, drowsy
-interacts w/ alcohol and narcotics
Somatosensation
Process by which sensory neurons are activated by external stimuli
Nociception
Process by which neural pathways are activated by tissue damaging substances
Pain Pathway
- Transduction
- Stimuli into action potentials - Transmission
- Conduction through nervous system - Modulation
- Alteration of conduction pathways - Perception
- Action potential into conscious sensation
Afferent Sensory-Pain Fibers
Aβ Fibers
- Heavily myelinated, large diameter = FAST
- Light Touch and Pressure
Aδ Fibers
- Lightly myelinated, smaller diameter = Fast (5-20m/s)
- Intense, stabbing pain. “First” pain.
C Fibers
- Unmyelinated, small diameter = Slow (2m/s)
- Burning. “Second”, delayed pain.
gabapentin/Neurontin
-unclear MOA; binds Ca+2 channels, possibly enhances GABAergic activity (but does not act at GABA receptors), alters concentration or metabolism of cerebral amino acids
-first line for neuropathic and chronic pain
-300mg po qhs x3d, then 300 bid x3d, then 300 tid thereafter with titration up to 3600 qd max. If elderly, start with 100mg instead.
-caution in renal failure or peripheral edema/R-CHF
AE: sedation, dizziness, ataxia, fatigue, peripheral edema/weight gain…
Anticonvusant
pregabalin/Lyrica
-unclear MOA; binds Ca+2 channels, possibly enhances descending NE and 5HT inhibitory pathways
-first line for FMS, neuropathic and chronic pain
-50mg po tid then titrate to 300 qd max
AE: same caution and SEs as neurontin, but seems to have less
Anticonvulsant
TCAs (ami/nortriptyline, desipramine/Norpramine) Tricyclic antidepressants
- unknown; felt to to be central 5HT and NE reuptake inhibitors
- second line for muscle relaxation
- 10-25qhs, inc 10-25qwk up to 150qd
- risk of suicide
- anticholinergic SEs: mydriasis, dry mouth, blurred viz, dizzy, sedation, constipation, urinary retention; but also many other SEs
Antidepressant
duloxetine/Cymbalta
- first line for FMS, MSK pain and neuropathic pain
- 30mg po qd x1wk then 60 qd max thereafter, ?120 qd
- risk of suicide, nausea, sedation…
- caution in adolescents with depression, liver disease
Antidepressant
tramadol/Ultram
-weak μ agonist, 5HT and NE RI
-first line opioid if considering chronic opioid use
-50-100mg po q6hrs (max 400 qd, 300 qd if elderly)
-caution with other opioids, alcoholics, seizure disorder
AE: vertigo, nausea, constipation, sedation…
acute and chronic pain
Topicals
lidocaine patch/Lidoderm
- topical anesthetic (NaCB)
- first line neuropathic pain
- 5% patch (may cut) to affected area on 12hrs, off 12hrs
- very safe
capsaicin/Zostrix
- second line neuropathic pain
- 0.025-0.075 % cream applied tid-qid
- “burns”, warm skin
topical diclofenac/Voltaren Gel
- topical NSAID
- first line osteoarthritis, especially small joints
- small amount to affected area qid
- caution in CV and GI disease, but very low SEs
