User:Guo9810/Analgesic adjuvant

An analgesic adjuvant is a medication that is typically used for indications other than pain control but provides control of pain in some painful diseases. They are used conjunction with traditional pain medications, such as acetaminophen, non-steroidal anti-inflammatory drugs, and opioids. This is often part of multimodal analgesia, where one of the intentions is to minimize the need for opioids.

Rationale
Multimodal analgesia refers to the use of multiple classes of medications in order to treat pain from different molecular mechanisms at once. Prolonged use of higher doses of opioids is associated with increased risk of tolerance and opioid use disorder, so there is a growing trend in the use of multimodal analgesia to treat pain.

Anticonvulsants

 * Anticonvulsants work through blockade of sodium and calcium ion channels to reduce glutamate (excitatory neurotransmitter) release.
 * Neuropathic pain is the result of nociceptor hyper-excitability due to damage to neurons that transmit pain.
 * Common agents used are gabapentinoids (calcium channel blockers) and carbamazapine (sodium channel blocker).
 * Gabapentin
 * Pregabalin
 * Carbamazepine: FDA-approved for trigeminal neuralgia
 * Some evidence that they may also help with inflammatory pain (nociceptor hyper-excitability due to damage to surrounding tissue)

Antidepressants

 * Antidepressants act by modulating serotonin transmission.
 * Descending serotonin pathways in spinal cord implicated in modulation of pain perception, especially in chronic pain.
 * Common agents used are serotonin-norepinephrine reuptake inhibitors (SNRIs) and tricyclic antidepressants (TCAs)
 * Duloxetine, venlafaxine, and amitriptyline are all FDA-approved for chronic musculoskeletal pain, peripheral neuropathy, and fibromyalgia)

Muscle Relaxants

 * Over-excitation of skeletal muscle can result in spasticity (increased muscle tone) and/or muscle spasms (involuntary muscle contractions) which may contribute to pain
 * Several different types of muscle relaxants used for pain with different mechanisms of action.
 * Cyclobenzaprine
 * Methocarbamol
 * Tizanidine
 * Baclofen
 * Carisoprodol: also active centrally and reduces perception of pain
 * Diazepam
 * Often have sedating effect that contributes to analgesia and improved relaxation
 * Some controversy over whether muscle relaxants are useful for acute musculoskeletal pain

Alpha-2 Adrenergic Agonists

 * Alpha-2 adrenergic agonists such as clonidine are traditionally used to treat hypertension by blocking sympathetic
 * Clonidine has been shown to have some efficacy when treating both acute and chronic pain.

Other Pharmacologic Compounds
Many other classes of pharmacologic compounds have been been found to have analgesic potential in certain situations. Several compounds used as adjunctive analgesics include antihistamines (hydroxyzine, promethazine), cannabinoids, NMDA receptor antagonists (ketamine, memantine), scopolamine, and caffeine.