442-MT2-CNS Muscle Relaxants & Anti-Migraine Drugs

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Author:
jgiantess
ID:
142169
Filename:
442-MT2-CNS Muscle Relaxants & Anti-Migraine Drugs
Updated:
2012-03-17 22:46:14
Tags:
pharmacology
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pharmacology
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  1. cyclobenzaprine
    • skeletal muscle relaxant
    • MoA: decreases activity of locus coeruleus, so decreases activity of descending facilitative influence on motor neuron excitability
    • decreases muscle tone (less flexion and extension)
    • aka "disfacilitation"
    • structurally similar to TCA
    • SE: antimuscarinic: sedation, confusion, dry mouth, dizziness, urinary retention
    • OoA: 1 hr
    • t1/2: 18 hrs
  2. methocarbamol
    • muscle relaxant
    • MoA: unclear...may suppress excitatory interneurons in spinal cord -> decrease amp of polysynaptic reflexes.
    • less excitatory drive to motor neurons -> muscle relaxation
    • said to decrease muscle tension without reducing basal muscle tone to maintain posture.
    • SE: sedation (v. significant), dizziness, blurred vision, dyspepsia, metallic taste
    • OoA: 30 mins
    • t1/2: 1-2 hours
  3. baclofen
    • GABA-mimetic, spasmolytic
    • agonist at GABAb receptors. does not requre presence of GABA for action.
    • reduces muscle spasticity, equally effective but less sedating than BZD
    • OoA: rapid after oral admin
    • t1/2: 3-4hrs
    • can be given intrathecally for refractory spasticity
  4. benzodiazepines (e.g. diazepam) for lower back pain
    • act on GABAa receptors but require GABA to exert action (not bind to same part as GABA)
    • enhances effect of GABA, increases frequency of chloride channel opening
    • OoA: almost immediate. oral 15-30mins.
    • t1/2: 5-50 hours (depends on metabolism and properties of diff agents)
    • SE: sedation, confusion, slurred speech, hypotension, brady, apnea
    • DEPENDENCE, withdrawal if stop. Important to taper dose.
  5. triptans
    • selective agonist for 5-HT1d and 5-HT1b receptors
    • e.g. suma, riza, nara, zoli, almo, ele
    • MoA: 1) bind to presyn 5-HT1d and inhibit release of neuropeptides, 2) direct VC/px of VD of meningeal bv, 3) block afferent input to 2o neurons in trigeminal nucleus caudalis.
    • PK: most effective when given in early stages of migraine (within 2 hours of onset). hepatic metab via MAO-A enzymes
    • dosage routes: PO, SL, intranasal, IV, IM
    • OoA: 15 mins with SC/IV
    • suma F 15%, newer agents F 50-70%, but not 100% so IV is most preferred.
    • SE: well tol'd...ass'd with stroke and CVD?
    • risk of serotonin syndrome if: MAOI in past 2 weeks, Ergot in last 24 hrs.
    • SSRIs and SNRIs not absolute CI...but must tell pt how to monitor for serotonin syndrome.
    • CI: ischemic vascular disease
  6. ergotamine
    • ergot alkaloid, purified
    • agonist, partial agonist, antagonist: 5-HT & alpha-adreno
    • agonist, partial agonist: dopamine receptors
    • MoA: VC of meningeal blood vessels. stronger affinity, up to 24 hours before dissociates from receptors.
    • dosage routes: IM, IV, SC, intranasal
    • SE: may worsen N/V, cause rebound headache, dependence, prolonged vasospasm
    • Administer with antiemetic.
  7. dihydroergotamine
    • ergot alkaloid, semi-synthetic
    • agonist, partial agonist, antagonist: 5-HT & alpha-adreno
    • agonist, partial agonist: dopamine receptors
    • MoA: VC of meningeal blood vessels. Higher affinity to alpha-adrenoreceptors, but lower receptor affinity vs. ergotamine for all other receptrs...mmore rapid hepatic elimination.
    • dosage routes: IM, IV, SC, intranasal
    • OoA: 15-30 mins
    • CI: hypertension, ischemic cardiovascular disease, current use of MAOI or strong CYP3A4 inhibs (azoles, macrolides)
    • SE: may worsen N/V, not cause rebound h/a or dependence.
    • Administer with antiemetic.
  8. metoclopramide (chlorpromazine, prochlorperazine)
    • antiemetic, used as monotherapy or adjunctive therapy in tx migraines
    • block dopamine and alpha-adrenoreceptors
    • - chemoreceptor trigger zone: decrease N/V
    • - trigeminovascular system: vasoconstriction...helpful for migraines?
    • metoclopramide enhances ACh action...accelerates gastric motility, increases lower esophageal sphincter tone.
    • SE: extra-pyramidal (akathisia, tardive dyskinesia, dystonia) if long term, and drowsiness

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