Fibromyalgia + muscle relaxants

Question 1

Treatments

Answer 1

Milnicipran (Savella)
Pregabalin (Lyrica)
Duloxetine (Cymbalta)

Question 2

Milnicipran (Savella)

Answer 2

• MOA: SNRI (selective serotonin and norepinephrine uptake inhibitor)
• USE: fibromyalgia in adults
• ADR: N/V/C, HA, dizziness, palpitations, tachycardia, hyperhidrosis
• Warnings: suicidal ideation; serotonin syndrome; elevated BP, tachycardia

Question 3

Muscle relaxants

Answer 3

dd

Question 4

Cyclobenzaprine (Flexeril, amrix)

- Adjunct to rest and PT for relief of muscle spasm associated with acute, painful musculoskeletal conditions

Answer 4

• Skeletal muscle relaxant (antispasmodic)
• Works at brain stem level, not spinal cord
• Some pharmacologic similarity to tricyclic antidepresants: potentiates NE, anticholinergic activity
• Not effective in the treatment of spasticity associated with cerebral or spinal cord dz, or in children with cerebral palsy
• ADR: dry mouth, sedation (anticholinergic effects)
• DRUG INTERACTIONS: MAOI (potentially fatal), EtOH and other depressants, increased seizure risk with tramadol
• CAUTION: urinary retention, acute angle closure glaucoma
• Renally eliminated
• Metabolized by CYP3A4, 1A2, 2D6

Question 5

Carisoprodol (Soma)

• FDA: acute treatment
• Adjunct to PT, rest for relief of acute, painful musculoskeletal conditions

Answer 5

• MOA not well known: centrally acting
• Metabolized to meprobamate in liver (anxiolytic, actions in thalamus and limbic system)
• ADR: drowsiness, dizziness, vertigo, ataxia, tremor; depression, agitation, irritability; syncope, insomnia; tachycardia, hyoptension; N/V; transient quadriplegia
• Long t1/2
• CIV

Withdrawal symptoms

• within 1st 3 days after abrupt cessation of large doses
• baseline by day 8
• restless, insomnia, anxiety, muscle twitches, incoordination, loss of appetite, N/V
• severe: agitation, hallucination, seizures
• treated with antipsychotics and BZDs

Question 6

Metaxalone (Skelaxin)

- Adjunct to rest, PT for relief of discomfort association w/ acute, painful musculoskeletal conditions

Answer 6

• MOA not well known: CNS depression, no direct muscle effect
• ADR: drowsiness, dizziness, HA, nervousness; N/V/GI upset; Leukopenia, hemolytic anemia; jaundice
• Interactions with other CNS depressants

Question 7

Methocarbamol (Robaxin)

Answer 7

Same MOA, same indications, same basic ADR

Question 8

Baclofen

• For muscle spasms due to multiple sclerosis, spinal cord injury, trigeminal neuralgia
• Off label: adjuvant treatment for cancer pain with muscle spasms

Answer 8

• GABA analog
• MOA: not well known (inhibits reflexes at the spinal level)
• ADR: drowsiness, dizziness, weakness, fatigue (some N/V, confusion)
• May have potential for treating addiction: opioid, cocaine, EtOH
• requires high dose

Question 9

Orphenadrine (Norflex, Norgesic)

Answer 9

• Analgesic
• Anticholinergic
• ADR: dry mouth, tachycardia, palpitation, urinary retention, blurred vision, mydriasis, increased IOP, weakness, N/V

Question 10

Chlorzoxazone (Parafon Forte, Lorzone)

- Pain relief

Answer 10

• Acts at spinal cord and subcortical brain areas
• Inhibits multisynaptic reflex arcs that produce and maintain skeletal muscle spasms (pain relief, increased mobility)
• well tolerated
• Associated with idiosyncratic hepatotoxicity

Question 11

Glucosamine Sulfate

- Improves pain and functionality compared to placebo in knee OA

Answer 11

• Amino sugar used for synthesis of mucopolysaccharides: part of cartilage proteoglycans, found in tendons, cartilage, ligaments, synovial fluid
• MOA: stimulates metabolism of chondrocytes in articular cartilage and synovial cells in synovial tissues; may have dz modifying effects in OA; my have activity against HIV

Cochrane

• Moderate benefit
• well tolerated: mild, GI side effects