Medication Summary
As outlined in the text, a wide variety of analgesic medications may be effective in the treatment of neuralgic pain. These include both narcotic and nonnarcotic medications.
Narcotic analgesics
Class Summary
Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have sustained trauma or injuries.
A review of opioid equivalents and conversions may be found in the following reference article:
http://emedicine.medscape.com/article/2138678-overview
Fentanyl transdermal patch (Duragesic, Sublimaze, Abstral, Actiq, Duragesic, Ionsys, Lazanda, Onsolis, Subsys)
Potent narcotic analgesic with much shorter half-life than morphine sulfate. DOC for conscious sedation analgesia. Ideal for analgesic action of short duration during anesthesia and immediate postoperative period.
Excellent choice for pain management and sedation with short duration (30-60 min) and easy to titrate.
Easily and quickly reversed by naloxone.
After initial dose, subsequent doses should not be titrated more frequently than q3h or q6h thereafter.
When using transdermal dosage form, pain in majority of patients controlled with 72-h dosing intervals; however, some patients require dosing intervals of 48 h.
Oxycodone (OxyContin, Oxaydo, Oxecta, Roxicodone, Xtampza ER)
Relieves moderately severe to severe pain.
Morphine sulfate (MS Contin, Duramorph, Astramorph, Depodur, Infumorph, Kadian, MorphaBond, Avinza, Arymo ER)
DOC for analgesia because of reliable and predictable effects, safety profile, and ease of reversibility with naloxone.
Various IV doses used; commonly titrated until desired effect attained.
For chronic severe pain unremitting to alternative therapy, oral immediate–release and extended-release morphine sulfate may be warranted. Arymo ER is a morphine sulfate abuse-deterrent formulation.
Methadone (Dolophine, Methadose, Methadose Sugar-Free)
Used in management of severe pain; inhibits ascending pain pathways, diminishing perception of and response to pain.
Oral analgesics
Class Summary
Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have sustained trauma or injuries.
Tramadol (Ultram, Active-Tramadol, ConZip, EnovaRX-Tramadol, Rybix, ODT, Synapryn FusePaq)
Inhibits ascending pain pathways, altering perception of and response to pain; also inhibits reuptake of norepinephrine and serotonin.
Tricyclic antidepressants
Class Summary
These agents are a complex group of drugs that have central and peripheral anticholinergic effects as well as sedative effects. They have central effects on pain transmission and block the active re-uptake of norepinephrine and serotonin.
Amitriptyline (Elavil)
By inhibiting re-uptake of serotonin and/or norepinephrine by presynaptic neuronal membrane, may increase synaptic concentration in CNS.
Useful as analgesic for certain chronic and neuropathic pain.
Nortriptyline (Pamelor)
Has demonstrated effectiveness in treatment of chronic pain.
By inhibiting reuptake of serotonin and/or norepinephrine by presynaptic neuronal membrane, may increase synaptic concentration in CNS.
Pharmacodynamic effects, such as desensitization of adenyl cyclase and down-regulation of beta-adrenergic receptors and serotonin receptors, also appear to play role in its mechanisms of action.
Anticonvulsants
Class Summary
These agents are used to manage severe muscle spasms and provide sedation in neuralgia. They have central effects on pain modulation.
Gabapentin (Neurontin, Fanatrex FusePaq, Gralise, Gralise Starter)
Has properties common to other anticonvulsants and has antineuralgic effects. Exact mechanism of action not known. Structurally related to GABA but does not interact with GABA receptors.
Lamotrigine (Lamictal)
Triazine derivative used in neuralgia. Inhibits release of glutamate and inhibits voltage-sensitive sodium channels, leading to stabilization of neuronal membrane.
Follow manufacturer's recommendation for dose adjustments.
Pregabalin (Lyrica)
Structural derivative of GABA. Mechanism of action unknown. Binds with high affinity to alpha2-delta site (a calcium channel subunit). In vitro, reduces calcium-dependent release of several neurotransmitters, possibly by modulating calcium channel function. FDA approved for neuropathic pain associated with diabetic peripheral neuropathy or postherpetic neuralgia and as adjunctive therapy in partial-onset seizures.
Anesthetics
Class Summary
These agents stabilize the neuronal membrane so the neuron is less permeable to ions. This prevents the initiation and transmission of nerve impulses, thereby producing the local anesthetic action.
Lidocaine anesthetic (ReadySharp Lidocaine, Xylocaine)
Several recent studies have advocated topical administration of lidocaine as treatment of PHN.
Lidocaine gel (5%) in a placebo-controlled study showed significant relief in 23 patients studied. Lidocaine tape also decreased severity of pain.
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Large-amplitude compound muscle action potential (CMAP) response was recorded from the right biceps muscle after intraoperative direct bipolar stimulation of the proximal right musculocutaneous nerve at low stimulus intensities (3.9 mA). The time base shown is 10 milliseconds/div and the gain is 50 mcV/div.
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Electrodiagnostic testing 1 day after the injury revealed the following: (Left) Right ulnar motor conduction study showed a normal distal amplitude with conduction block across the elbow segment (gain = 2 mV/div, time base = 2 milliseconds [ms]/div). (Second from left) Right ulnar sensory response was normal (gain = 20 mcV/div, time base = 2 ms/div). (Third from left) Right ulnar F-wave responses were absent. (Right) Needle electromyographic (EMG) examination of right abductor digiti minimi was quiet at rest but showed a single fast firing unit on attempted contraction (gain = 200 mcV/div, time base = 10 ms/div).
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Electrodiagnostic testing 3 days after the injury revealed the following: (Left) Right distal ulnar motor response is of lower amplitude than on day 1, approximately 50% of baseline (gain = 2 mV/div, time base = 5 milliseconds [ms]/div) with persistent conduction block across the elbow. (Right) Right ulnar sensory response is still normal (gain = 20 mcV/div, time base =2 ms/div).
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Electrodiagnostic testing 6 days after the injury revealed the following: (Left) Right distal ulnar motor response is less than 10% of baseline (gain = 2 mV/div, time base = 5 milliseconds [ms]/div) with persistent conduction block across the elbow. (Right) Right ulnar sensory response amplitude still is relatively preserved at 50% of baseline (gain = 20 mcV/div, time base = 1 ms/div).
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Electrodiagnostic testing 10 days after the injury revealed the following: Right ulnar motor (middle) and sensory (right) responses are absent. Needle electromyography (EMG) of first dorsal interosseus shows sparse denervation potentials with 1 fast firing unit on attempted volitional activity.
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Intraoperative nerve action potentials recorded from the lateral cord (point R) with successive stimulation (at points 1, 2, 3, 4, and 5) along the course of the musculocutaneous nerve (gain = 100 mcV/div, time base = 0.5 milliseconds [ms]/div). Normal responses are recorded from stimulation at points 1 and 2. A slight increase in latency and drop in amplitude are noted on stimulation at point 3 close to the nerve injury. Stimulation at points 4 and 5 (distal to the injury) fail to evoke a recordable response.
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A 25-year-old man had a "flail" right arm after injury in a motorcycle accident (Case study 4). Left panel: Somatosensory evoked potentials (SEPs) recorded at the scalp from stimulation of the (healthy) middle trunk (gain = 0.2 mcV/div, time base = 10 milliseconds [ms]/div). Middle panel: SEPs recorded at the scalp from stimulation of the lower trunk—no reproducible responses present (gain = 0.2 mcV/div, time base = 10 ms/div). Right panel: "Super normal" nerve action potentials recorded at the lower trunk from stimulation of the medial cord (time base = 1.5 ms/div, gain = 20 mcV/div).
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MRN of the brachial plexus. a: Abnormal signal in the brachial plexus elements on the affected (right) side. Compare to b: normal plexus on the unaffected (left) side.
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MRN image through the cervical spine showing pseudomengocele (arrows) at the site of a cervical root avulsion in a patient with traumatic brachial plexopathy.
