12 - Pain 2 Flashcards
What are skeletal muscle relaxants?
Group of agents that act predominantly w/in CNS to relieve pain associated w/ skeletal muscle spasms
Which OTC products are skeletal muscle relaxants?
- Methacarbamol (most common; most often in combination w/ analgesic)
- Chlorzoxazone (less common)
- Orphenadrine
What is the MOA, indication, and onset of methocarbamol? Is it used as a first line agent?
- MOA = unknown, thought to cause skeletal muscle relaxation due to general CNS depression
- Indication = tx of acute, painful, musculoskeletal muscle spasms
- Onset = 12-24 h
- Not first line b/c of SE
What is the MOA, indication, and onset of orphenadrine? Is it used as a first line agent?
- MOA = mechanisms similar to analgesic and anti-cholinergic properties; exact MOA unknown
- Indication = tx of painful muscle spasms due to acute musculoskeletal conditions
- Onset = more than 24 h
- Not first line b/c of SE
What is the MOA and indication for chlorzoxazone?
- MOA = muscle relaxant due to central acting properties; works at spinal cord and brain level to decrease skeletal muscle spasms
- Indication = acute relief of pain and discomfort due to musculoskeletal conditions
What are SE of methocarbamol?
- Drowsiness, dizziness
- Light-headedness, headache
- Urine discolouration (black, blue, green, or brown)
What are CIs of methocarbamol?
- Pregnancy
- Caution in px w/ seizure disorder, hepatic or renal impairment
What are SE of orphenadrine?
- CNS (drowsiness, dizziness, headache)
- Anticholinergic effects (constipation, dry mouth, blurred vision)
What are SE of chlorzoxazone?
- CNS (drowsiness, dizziness, headache)
- Urine discolouration (orange to purple/red)
- Impaired hepatic function
What are CI of orphenadrine?
- Pregnancy
- Caution in px w/ seizure disorder, hepatic or renal impairment
- Anticholinergic (glaucoma, prostate hypertrophy, arrhythmias)
What are drug-drug interactions for all of the skeletal muscle relaxants?
- Other ACh agents
- CNS depressants
- MAO inhibitors
- Alcohol
What are the most commonly used topical analgesics?
Those w/ counterirritant effects
What is the MOA of counterirritants?
- Paradoxical pain (produce a less severe pain to counter a more intense one)
- Produce mild, local inflammatory reaction
Which ingredients are considered “heat” therapy?
- Methyl salicylate
- Capsaicin
- Trolamine salicylate
Which ingredients are considered “cold or ice” therapy?
Menthol or camphor
Which ingredient is used in no odour products?
Trolamine salicylate
What are some precautions w/ methyl salicylates and trolamine salicylate?
- Avoid use when taking anticoagulants
- Avoid use if allergic to salicylates
- Caution w/ salicylate sensitive asthmatics
What is the length of treatment for counterirritants?
Maximum 7 days, except capsaicin (usually 14 days, but may need a max. of 4-6 weeks)
What effect does capsaicin produce once applied?
Produces a transient feeling of warmth, but diminishes w/ repeated applications
What is the MOA of capsaicin?
Reduces substance P in sensory neurons (responsible for transmission of pain impulses)
When is capsaicin used? When is it not used?
- Used in osteoarthritis pain, postherpetic neuralgia, and lower back pain
- Not used on wounds or damaged skin
What are some instructions specific for capsaicin?
- Must apply at least 3x/day to provide pain relief and for burning sensation to diminish
- Burning sensation will diminish w/ regular use
- Apply for 3-4 weeks for optimal response
- Discontinue if condition worsens or doesn’t improve after 28 days
What are topical NSAID analgesics used for?
Relief of muscle, joint, and back pain
What is the recommended length for topical NSAID analgesics?
Short term (7 days)
What is a benefit to topical NSAIDs?
For some conditions (ex: osteoarthritis), provide similar pain relief properties as oral NSAIDs w/o the GI adverse effects
What is the dosing for diclofenac diethylamine gel (Voltaren Emulgel)?
- Apply over affected area 3-4 times daily and rub gently into skin
- Apply twice daily for extra strength (2.32%)
- Wash hands before and after application
What are the categories of back pain?
- Acute = less than 4 weeks
- Sub-acute = 4-12 weeks
- Chronic = over 12 weeks
What is normally the cause of acute low back pain?
Sprain or strain of muscles or ligaments that support the lumbar spine
What are less common causes of low back pain? Do any of these require referral?
- Inflammation or traumatic injury to joints and ligaments
- Disc injury
- Neurological involvement
- Arthritis
- Malignancy and infection
- All require referral
What are sx of low back pain?
- Range from muscle ache to spasm
- Involves low back, buttock, and posterior thigh
What are risk factors for low back pain?
- Age (peak = 45-64 y/o)
- Occupation
- Posture
- Height and weight
- Pregnancy
- Smoking
- Stress
What are red flags for low back pain?
- Pain in middle to upper back
- Pain for more than 5 days
- Bladder or sexual dysfunction
- Fever/chills; vertebral tenderness
- Age over 50 or under 20 y/o
- Constant pain; nighttime pain; no relief w/ postural change
- Loss of movement or range of motion
- Unexplained weight loss
- Chronic liver disease; inflammatory arthritis
- Weakness/numbness or tingling in legs
- Long-term steroid use
- High risk for fractures
- No improvement to tx after 1 month
- Visceral pain (organs)
What are the recommendations for tx of low back pain?
- Greater self-reliance
- Return to activity ASAP
- Stay active
- Avoid de-conditioning and debilitation
What are non-pharms for low back pain?
- Cryotherapy (first 24-48 hours, up to 72 h)
- Thermotherapy
- Exercise
- Rest only if essential (1-3 days max.)
- Improve coping skills (control/avoid anxiety or depression)
What are pharm options for low back pain?
- Internal analgesic (acetaminophen, ibuprofen/naproxen, ASA, codeine combinations)
- Skeletal muscle relaxants
- Topical analgesics (methylsalicylate/ capsaicin/ menthol; diclofenac gel)
Should skeletal muscle relaxants be recommended for acute low back pain?
- Not 1st line
- Better than placebo but no better than NSAIDs
- Can use short term (2-3 days) as a sedative and/or analgesic agent
What is the recommended pharm approach for acute low back pain?
- Acetaminophen if no inflammation present
- NSAIDs based on co-morbidities
- NSAIDs given at full dose for pain w/ inflammation; use for 2-4 weeks
- Dose both on regular schedules
What are non-pharms for prevention of low back pain?
- Follow a program emphasizing flexibility
- Aerobic conditioning
- Proper posture
- Proper use of body mechanics
- Weight loss
What is the monitoring for low back pain?
- Improvement in 7-10 days
- Continue everyday activities w/in limits permitted by pain
When should a px be referred after they have tried tx for low back pain?
- Loss of motion or sensory function
- Increasing pain
- Loss of bladder and bowel function
- Failed tx (trial of at least 2 analgesics for 2-4 weeks each)
- Any other red flags
What is a muscle strain?
Muscle fibres pulled apart causing pain, reduced movement, and sometimes swelling (aka pulled muscle)
What is a muscle contusion?
Damage to blood vessels in muscles followed by bleeding, bruising, and sometimes clotting
What is tenosynovitis?
- Tendon is irritated and inflamed
- Causes pain, swelling, and sometimes crackling sound when moving
When does damage occur to tendons?
When extended or overused
What is the difference between tendons and ligaments?
- Tendons join muscles to bone
- Ligaments join bone to bone to form joints
What are the categories of ligament sprains?
- 1st degree = excessive stretching
- 2nd degree = partial tear
- 3rd degree = complete tear of tissue
What are red flags for muscle strains and sprains?
- Severe pain or weakness in any limb
- Visually deformed joint or abnormal joint movement
- Joint pain w/ systemic symptoms (fever)
- Suspected or obvious fracture
- Increased intensity of pain or any change in character of pain
- Inability to bear any weight on injured limb
- Pain lasting longer than 2 weeks
- Swelling lasting more than 14 days after RICE therapy
What is RICE therapy?
- Rest
- Ice (20 mins) to reduce pain, inflammation and bruising
- Compression to help swelling go down (don’t wrap too tight)
- Elevation - keep injured area above heart to reduce swelling
What are non-pharms for muscle strains and sprains?
- RICE therapy
- Thermotherapy
- Rehabiliation
What are pharm options for muscle strains and sprains?
- Internal analgesics (acetaminophen, ibuprofen/naproxen, ASA)
- Topical analgeics (counterirritants)
What is the no HARM principle of tx for muscle strains and sprains?
- No heat, alcohol, running or massage (increases bleeding, swelling, or can make injury worse)
- Applies to acute stage of injury for 24-48 hours
What is the benefit of cryotherapy in acute injuries?
- Decreases metabolism and inflammation
- Slows nerve conduction
- Vasoconstriction => decreased edema and hemorrhage
In which group of px should cryotherapy be used w/ caution?
Px in which vasoconstriction is already a problem
What are the directions for use of cryotherapy?
- Use a gel pack (cooled in fridge not freezer), bag of frozen peas, or cold compress
- Place wet towel or cloth between skin and ice to prevent frostbite
- Apply for 20 mins or until skin feels numb, whichever is shorter
- Repeat q2h until swelling decreases (2-48 h)
What is the benefit of heat for sub-acute injuries (after 48 h)?
- Produce vasodilation
- Increases tissue perfusion of oxygen and nutrients
- Helps w/ removal of CO2, waste, and pain mediators
- Relaxes muscle and can decrease muscle spasms
In which px groups should heat be used w/ caution or avoided?
- Active bleeding
- Fresh hematoma/bruise
- Caution in px w/ sensitive skin (won’t be able to tell if being burned)
- Rheumatoid arthritis (heat can activate enzymes that damage cartilage)
Which topical product is the best option for muscle strains and sprains?
Topical NSAIDs b/c have anti-inflammatory properties, so are actually treating the problem w/ few SE
What is the monitoring for a grade 1 ankle injury?
- Improvement in swelling and discomfort in 48 hours
- Should be able to move the ankle
- 7-10 days of therapy
When should a grade 1 ankle injury be referred?
- Ankle is extremely painful
- Swelling and discolouration doesn’t subside or worsens
- Impossible to bear weight on affected leg
- Obvious deformity
Is osteoarthritis an inflammatory disorder?
Typically non-inflammatory, but later stages can include inflammation issues
What is the pathophys of osteoarthritis?
- Initially, cartilage thickens, but eventually cartilage softens and pieces break off
- Cartilage deteriorates resulting in bone against bone, leading to changes in bone
What are risk factors for osteoarthritis?
- Advancing age
- Female
- Obesity
- Occupation
- Family history/genetics
- Joint injury or surgery
- Joint overuse or injury w/ certain sports
- Quadriceps muscle weakness
What are signs and sx of osteoarthritis?
- Pain - initially felt near the joint, aggravated w/ activity or prolonged use
- Joint stiffness - occurs in mornings or after time of non-use; generally lasts less than 30 mins
- Occasional joint instability
- As condition progresses, may have bony swelling
What is the treatment plan for OA?
- Requires diagnosis
- Tx progression should correlate w/ disease progression
- Tx focused on sx relief
What are some non-pharms for OA?
- Lifestyle changes (weight loss of at least 5%)
- Exercise (strength training and aquatic exercises)
- Joint protection (splints, taping, braces)
- Improve footwear
- Occupational or physiotherapy
- Reduce “mechanical” stresses or use ambulation aids (canes, walkers)
- Stress management
- Heat
- Massage
What is the drug of choice for OA?
- Acetaminophen up to 1 gram QID (lowest effective dose should be used)
- Trial for 1-2 weeks
What is the recommended tx for OA for px w/ incomplete relief w/ acetaminophen?
- Topical agents (diclofenac, capsaicin)
- Topical NSAIDs preferred over oral in px 75 years and older
- Max. effect = 2 weeks for topical NSAID, 4 weeks for topical capsaicin
- Oral NSAIDs are second line; must assess risks from CV, GI, and renal complications before starting
What is the minimum single toxic dose of acetaminophen?
7.5-10 g over an 8 hour period
