Radiation-Induced Lumbosacral Plexopathy Medication

Tricyclic antidepressants (TCAs), such as amitriptyline, may be used in lower doses. The use of antiepileptics may be helpful.

Class Summary

TCAs have central and peripheral anticholinergic effects, as well as sedative effects, and block the active reuptake of norepinephrine and serotonin. The multifactorial mechanism of analgesia may include improved sleep, an altered perception of pain, and an increase in pain threshold. The efficacy of these drugs can be potentiated with the concomitant use of opiates and nonsteroidal anti-inflammatory drugs (NSAIDs). Rarely should these drugs be used in the treatment of acute pain, since a few weeks may be required for them to become effective.

Amitriptyline (Elavil)

Analgesic for certain chronic and neuropathic pain. Amitriptyline has the most anticholinergic side effects of all drugs in this category.

Class Summary

These drugs stabilize neuronal membranes and reduce neuronal hyperexcitability. The analgesic effect may be due to such stabilization and control of hyperexcitability, because aberrant electrical activity has been recorded with neuropathic pain.

Gabapentin (Neurontin)

Has anticonvulsant properties and antineuralgic effects; however, the exact mechanism of action is unknown. Gabapentin is structurally related to GABA but does not interact with GABA receptors.

Carbamazepine (Tegretol)

Used typically for generalized tonic-clonic seizures and partial seizures, as well as for trigeminal neuralgia. Plasma levels are between 4-12 mcg/mL for analgesic and antiseizure response.

Valproic acid (Depakene)

Generally indicated for absence seizures and generalized tonic-clonic seizures. Some relief may be noted with neuropathic pain, especially the lancinating type.

Class Summary

Glucocorticoids have anti-inflammatory, hormonal, and metabolic effects. Inflammation is suppressed with the blockage of phospholipase A2, which inhibits the formation of arachidonic acid and, thus, the prostaglandins. The analgesic effect may be due to the anti-inflammatory activity, with a decrease in edema.

Dexamethasone (Decadron, AK-Dex)

For various allergic and inflammatory diseases. Dexamethasone decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and by reducing capillary permeability.

Class Summary

These drugs are generally used for short-term, acute pain that is moderate to severe in nature, as well as for chronic pain (eg, cancer). They provide analgesia without antipyretic or anti-inflammatory action. The mechanism of action is the inhibition of nociceptive impulses at the dorsal horn of the spinal cord and at supraspinal sites due to interaction with opiate receptors. Structural derivatives of GABA are also used in the management of neuropathic pain.

Pregabalin (Lyrica)

Structural derivative of GABA. Pregabalin's mechanism of action is unknown. This agent binds with high affinity to the alpha₂ -delta site (a calcium channel subunit). In vitro, pregabalin reduces the calcium-dependent release of several neurotransmitters, possibly by modulating calcium channel function. It is FDA approved for neuropathic pain associated with diabetic peripheral neuropathy or postherpetic neuralgia and as an adjunctive therapy in partial-onset seizures.

Methadone (Dolophine)

Used in the management of severe pain. Methadone inhibits ascending pain pathways, diminishing the perception of and response to pain.

Morphine sulfate (Duramorph, MS Contin, Astramorph)

Available in immediate (3-4 h duration) and extended release preparation (12 h). Switch over to long-acting preparations (MS Contin) once pain is controlled with short-acting preparation (MS IR). Morphine can produce drug dependence and has the potential for being abused. Tolerance may develop with repeated exposure. Abrupt cessation or sudden reduction in dose with prolonged use may result in withdrawal symptoms. Physical dependence is not of paramount importance in terminally ill patients.