Medication Summary
Pharmacologic interventions for the relief of low back pain (LBP) include acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), topical analgesics, muscle relaxants, opioids, corticosteroids, antidepressants, and anticonvulsants.
Acetaminophen remains one of the best first-line treatments of acute LBP. It is generally well tolerated, has few adverse effects or drug reactions with other medications, and is inexpensive. Acetaminophen is as effective as aspirin; however, overdoses can result in fatal hepatic injury. The maximum advised dose is 4 g/d.
NSAIDs are the most frequently prescribed analgesic medications for mechanical LBP worldwide. A review of the Cochrane Controlled Trials Registry found 51 randomized control trials (involving 6057 patients) comparing different NSAIDs for the treatment of acute mechanical LBP. [41] NSAIDs were found to be effective for short-term symptomatic relief. No specific type was shown to be clearly more effective than the others. Insufficient evidence was found for effective analgesic control in chronic LBP.
NSAIDs augmented with muscle relaxants are a standard medical prescription for LBP in the primary care setting. These agents should be prescribed on a scheduled basis, rather than as needed, for optimal analgesia. Patients on combined NSAIDs and muscle relaxants report reduction of symptoms at 1 week, which is less than when compared with either drug alone. The optimum combination of NSAIDs and muscle relaxants remains to be determined.
Topically applied lidocaine patches (Lidoderm 5% patch) have provided a reduction in pain intensity and pain relief in clinical trials of patients with acute pain.
Opioid medications are mainstays for short-term treatment of severe pain. Their role in the long-term care of patients with mechanical LBP is the subject of intense investigations. Transdermal opioid (fentanyl) has been shown to compare favorably to oral long-acting opioids. Concerns about drug diversion and abuse continue to cloud the benefits of long-term opioid use for LBP.
Corticosteroids may play a role in the treatment of mechanical LBP with acute radiculopathic features of radiating pain down one or both legs.
Antidepressants are thought to be effective when a component of depression is accompanying the mechanical LBP. Antidepressants may contribute to improving the disruption in sleep that patients frequently mention as a part of the constellation of symptoms resulting from LBP.
The basic mechanism of anticonvulsants is to stabilize neural membranes. This concept has been used to support the use of anticonvulsants for adjunct analgesia suspected to come from neuropathic causes.
Botulinum toxin type A has been investigated for pain relief in several small studies. The toxin temporarily paralyzes the lumbar muscles, which may be creating spasms that contribute to the generation of LBP.
Clinicians have found that long-acting oral opioids can be rotated periodically (eg q6-12mo) to maintain effectiveness. The molecular structures of these compounds may be sufficiently different to opioid receptors to counter the affects of diminished and down-regulation of receptors to chronic opioid exposure.
Pharmaceutical companies are exploring various combinations of NSAIDs/opioids, extended-release formulations, and drug delivery (eg topical, mucosal) in an effort to achieve safe and effective pain control.
Analgesic agents
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 have sustained injuries. The FDA has cleared duloxetine to treat chronic musculoskeletal pain. [42]
Acetaminophen (Tylenol, Feverall, Tempra)
DOC for pain in patients with documented hypersensitivity to aspirin or NSAIDs, with upper GI disease, or who are taking oral anticoagulants.
Duloxetine (Cymbalta)
Potent inhibitor of neuronal serotonin and norepinephrine reuptake. Indicated for chronic musculoskeletal pain, including discomfort from osteoarthritis and chronic lower back pain.
Nonsteroidal anti-inflammatory drugs
Class Summary
Have analgesic, anti-inflammatory, and antipyretic activities. [41] Mechanism of action is not known, but they may inhibit COX activity and prostaglandin synthesis. Other mechanisms may also exist, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell-membrane functions.
Aspirin (Anacin, Ascriptin)
Effective in most mechanical LBP cases. Irreversibly inhibits platelet function, leading to prolonged bleeding times.
Naprosyn (Naproxen, Naprelan, Naprosyn)
For relief of mild to moderate pain; inhibits inflammatory reactions and pain by decreasing activity of COX, which results in a decrease of prostaglandin synthesis.
Cyclooxygenase II inhibitors
Class Summary
Although increased cost can be a negative factor, the incidence of costly and potentially fatal GI bleeding is clearly less with COX-2 inhibitors than with traditional NSAIDs. Ongoing analysis of cost avoidance of GI bleeds will further define the populations that will find COX-2 inhibitors the most beneficial.
Celecoxib (Celebrex)
Inhibits primarily COX-2. COX-2 is considered an inducible isoenzyme, induced during pain and inflammatory stimuli. Inhibition of COX-1 may contribute to NSAID GI toxicity. At therapeutic concentrations, COX-1 isoenzyme is not inhibited, thus GI toxicity may be decreased. Seek lowest dose of celecoxib for each patient.
Muscle relaxants
Class Summary
Mechanism of action is not fully understood.
Cyclobenzaprine (Flexeril)
Skeletal muscle relaxant that acts centrally and reduces motor activity of tonic somatic origins, influencing alpha and gamma motor neurons.
Structurally related to TCAs and thus carries some of their same liabilities. Given in combination with an NSAID (similar to carisoprodol).
Orphenadrine (Norflex)
While exact mode of action not well understood, has shown clinical effectiveness in muscular injury. Effectiveness may be related to analgesic properties. May have atropinelike effects and analgesic properties.
Carisoprodol (Soma)
Short-acting medication that may have depressant effects at spinal cord level. Often given in combination with an NSAID.
Opioids
Class Summary
Useful only for extremely severe pain. Can be administered by injection.
Oxycodone (OxyContin)
Indicated for relief of moderate to severe pain. Use of this medication should be discussed with the prescribing physician due to numerous concerns, including with regard to addiction, abuse, diversion, and overdosing.
-
Magnetic resonance image of the lumbar spine. This image demonstrates a herniated nucleus pulposus at multiple levels.
-
Diskogram showing examples of an intact disk and a disrupted disk at the lumbar level.
-
Sagittal magnetic resonance image showing loss of intervertebral disk height at L5/S1. Herniations of the nucleus pulposus are noted at L4/5 and L5/S1.
-
Degenerative changes of the lumbar spine, including decreased signal intensity and disk bulging at the L-3/4, L-4/5 and L-5/S-1 disks.
-
The process of disk degeneration following internal disk disruption and herniation.
-
The various forces placed on the disks of the lumbar spine that can result in degenerative changes.
Tables
Nerve Root |
Motor Examination |
Functional Test |
L3 |
Extend quadriceps |
Squat down and rise |
L4 |
Dorsiflex ankle |
Walk on heels |
L5 |
Dorsiflex great toe |
Walk on heels |
S1 |
Stand on toes* |
Walk on toes (plantarflex ankle) |
*When testing the S1 innervated gastrocnemius muscle, the ability to stand on the toes once represents fair (3/5) strength. The patient must stand on his or her toes 5 times in a row to be rated normal (5/5) strength. Note that this approach should allow the physician to detect weakness at a much milder stage than if gastrocnemius strength were assessed only by using the examiner's hand to apply resistance to ankle plantar flexion. |
||
Nerve Root |
Pin-Prick Sensation |
Reflex |
L3 |
Lateral thigh and medial femoral condyle |
Patellar tendon reflex |
L4 |
Medial leg and medial ankle |
Patellar tendon reflex |
L5 |
Lateral leg and dorsum of foot |
Medial hamstring |
S1 |
Sole of foot and lateral ankle |
Achilles tendon reflex |
