Low Back Pain
Clinical Snapshot
Low back pain is pain, muscle tension, or stiffness localized below the costal margin and above the inferior gluteal folds, with or without pain referred into the leg (sciatica). The overwhelming majority of cases are nonspecific (mechanical) low back pain -- no single structural finding on imaging reliably explains the pain, and imaging findings correlate poorly with symptoms even in people without any back pain at all.[1] Management is staged by duration: acute (roughly the first 4 weeks, sometimes defined as 0-30 days), subacute (4 to 12 weeks), and chronic or persistent (over 12 weeks) low back pain, with sciatica -- pain referred below the knee, with or without a demonstrable radiculopathy -- treated as a distinct but overlapping presentation. The single highest-yield task at every visit, regardless of duration, is a brief screen for the small minority of patients with a serious underlying cause -- cauda equina syndrome, malignancy, infection, or fracture -- since missing one of these has far greater consequence than a delay in treating routine mechanical pain.
Recognize the Condition
Nonspecific (mechanical) low back pain
Axial low back pain that worsens with movement or prolonged static posture and improves with rest or position change, without radiation below the knee and without a demonstrable neurologic deficit. This is the presentation in the large majority of patients and does not require imaging or a specific structural diagnosis before starting treatment.
Sciatica
Pain referred from the back into the leg, below the level of the knee. There are two distinct patterns: sciatica with radiculopathy, where a specific nerve root lesion is demonstrable on neurologic exam, electromyography, CT, or MRI (most often from a herniated disc compressing a nerve root); and sciatica without radiculopathy, a referred-pain mechanism without a demonstrable focal nerve root lesion. The distinction matters because radiculopathy points toward a specific anatomic cause and a specific dermatomal exam pattern (see Assessment & Diagnosis), while nonradicular referred sciatica is managed the same as nonspecific low back pain.
Duration-based staging
Every patient is classified into one of these tracks at presentation -- it determines the intensity and focus of management.
Acute (under 4 weeks)
The goal is rapid functional recovery and reduced pain-related distress. Prognosis is favourable -- most patients improve substantially within the first several weeks regardless of the specific treatment chosen, which is why avoiding over-treatment (bed rest, premature imaging, opioids) matters as much as treating the pain itself.
Subacute or recurrent (4-12 weeks)
The goal shifts to preventing progression to chronic pain and disability, and preventing or minimizing prolonged work absence. This is the critical window for active, coordinated intervention -- delaying escalation past 4 weeks of unresolved symptoms and work absence measurably worsens the odds of full recovery.
Chronic or persistent (over 12 weeks)
The goal becomes restoring function, fitness, and role participation (including work) by addressing both physical and psychological contributors to persistent pain -- complete pain resolution is often not achievable and should not be the sole marker of treatment success at this stage.
Risk Factors
Risk factors for developing low back pain
- Heavy manual labour, repetitive lifting, bending, or twisting.
- Prolonged sitting or a sedentary lifestyle.
- Obesity.
- Smoking.
- Poor physical conditioning and reduced core/trunk strength.
- Prior episode of low back pain -- the strongest predictor of a future episode.
- Pregnancy (see Special Populations).
Risk factors for chronicity ("yellow flags") -- screen for these explicitly by 4-6 weeks if symptoms or work absence persist
- Duration of work absence to date, and a history of prolonged sick-listing after previous injuries or prior absenteeism.
- High self-reported functional disability, or self-reported extreme and constant pain across multiple body areas.
- Delays or obstacles in the work re-entry process, an adversarial attitude toward the employer, or a belief that one will never return to work.
- A long-standing history of psychiatric distress or maladjustment.
- Compensation or litigation in progress, particularly where compensation levels are high or the patient is in active conflict with the employer or insurer.
- Mental-status indicators of significant anxiety or depression: insomnia or nightmares, irritability, social withdrawal, panic episodes, persistent tearfulness, poor concentration, anhedonia (inability to enjoy activities), and poor appetite or libido.
- Any expression that life is not worth living needs the same urgent same-day mental health assessment it would in any other clinical context -- do not let it pass unaddressed as just a pain symptom.
Red Flags & Refer
Screen for these at every visit. No single red flag reliably confirms serious pathology on its own -- taken individually, red flags only modestly increase the probability of a serious diagnosis, and their absence does not reliably exclude one -- but a combination of two or more red flags clearly increases the likelihood and should prompt further work-up.[2]
- Cauda equina syndrome (emergency -- same-day neurological assessment and emergency MRI of the lumbosacral spine): acute urinary retention or overflow incontinence, loss of anal sphincter tone or fecal incontinence, saddle (perineal) numbness, new sexual dysfunction, or bilateral or progressively worsening leg weakness.
- Suspected malignancy: age over 50, a personal history of cancer, unexplained weight loss, or failure to improve after 1 month of guideline-concordant treatment.
- Suspected spinal infection (epidural abscess, discitis, or osteomyelitis): intravenous drug use or another source of infection, fever, pain unrelieved by rest or position change, sensory loss, paraparesis or quadriparesis, or new bowel/bladder impairment.
- Suspected vertebral fracture: age over 50, female sex, a history of significant trauma (or low-velocity trauma in a patient with osteoporosis or chronic corticosteroid use), or a distracting painful injury.[3]
- Progressive or severe neurologic deficit of any cause, or new bowel/bladder dysfunction short of the full cauda equina picture above -- both need urgent (not routine) neurologic and imaging assessment.
Assessment & Diagnosis
Differentiating serious spinal pathology from mechanical low back pain
Because several of these serious causes can present with pain alone at their earliest stage, use this table alongside the red-flag list above rather than waiting for a fully developed presentation.
| Condition | Key features suggesting this diagnosis | Recommended investigation |
|---|---|---|
| Cauda equina syndrome | Acute urinary retention or overflow incontinence; loss of anal sphincter tone or fecal incontinence; saddle numbness; new sexual dysfunction; bilateral or progressive leg weakness | Emergency neurological assessment and emergency MRI of the lumbosacral spine |
| Spinal malignancy | Age over 50; personal cancer history; unexplained weight loss; failure to improve after 1 month of treatment | Laboratory testing (ESR, CBC) and MRI or CT with contrast |
| Spinal infection (epidural abscess, discitis, osteomyelitis) | IV drug use or another infection source; fever; pain unrelieved by position change; sensory loss, paraparesis, or bowel/bladder impairment; vertebral tenderness | Laboratory testing for infection source, urine drug screen, MRI of the spine |
| Vertebral fracture | Age over 50, female sex, significant trauma (or low-velocity trauma with osteoporosis/chronic corticosteroid use), a distracting painful injury | Plain radiographs of the spine |
| Herniated disc with radiculopathy | Positive straight leg raise (leg pain reproduced below 60° of elevation); weak ankle dorsiflexion (L4-L5) or great toe extension (L5-S1); reduced ankle reflex (L5-S1); dermatomal sensory loss | MRI of the lumbar spine, but only if surgery/injection is being considered or a red flag is present |
History
- Onset, duration, character, and location of pain; whether pain radiates below the knee (sciatica); aggravating and relieving factors.
- Explicit screen for every red flag above at the first visit, and again at any reassessment.
- Explicit screen for yellow flags (see Risk Factors) by 4-6 weeks if symptoms or work absence have not resolved.
- Prior episodes, prior treatment response, and current medication use including any recent antibiotic, corticosteroid, or anticoagulant use.
Physical examination
- Observe gait, including heel walking (tests L4-L5) and toe walking (tests S1), and watch for a Trendelenburg gait pattern (suggests L5 weakness).
- Standing: modified Schöber test (lumbar flexion range), trunk lateral bending, and spine extension.
- Sitting: patellar reflex and quadriceps power (L3-L4); ankle dorsiflexion power (L4-L5) and ankle plantarflexion power (S1); great toe extension (L5) and flexion (S1); straight leg raise (SLR) test with a Slump test to check consistency; FABER (Patrick’s) test to screen for hip/sacroiliac pathology as a mimicker of radicular pain.
- Lying prone: femoral nerve stretch test (assesses L3-L4 root tension) and saddle sensation testing (S2-S4, screens specifically for cauda equina).
- Sensation: dermatomal light touch and pinprick testing from L3 to S2; generalized diffuse tenderness across trunk and all four limbs raises suspicion for a centralized or nonorganic pain pattern rather than a focal lesion.
| Nerve root | Motor | Sensory | Reflex |
|---|---|---|---|
| L3-L4 | Knee extension (quadriceps) | Anteromedial thigh, medial leg | Patellar (knee-jerk) |
| L4-L5 | Ankle dorsiflexion; great toe extension | Lateral leg, dorsum of foot | No reliable primary reflex for L5 |
| S1 | Ankle plantarflexion; ankle eversion | Lateral foot, sole | Ankle (Achilles) |
Diagnostic imaging
Imaging is not recommended for uncomplicated acute, subacute, or chronic low back pain, or for radiculopathy, when no red flag is present -- imaging findings are common in people who have no back pain at all, correlate poorly with symptoms, carry poor prognostic value when ordered without a red flag, and are associated with an increased likelihood of unnecessary surgery.[4][1]
Reserve MRI (or CT with contrast where MRI is unavailable) for a patient with a red flag, or one of these specific risk factors: low-velocity trauma, osteoporosis, older age, chronic corticosteroid use, suspected cancer, suspected infection, or immunosuppression. Imaging is also reasonable for a surgical candidate with persistent or progressive symptoms after 6 weeks of conservative management, new or progressive neurologic findings, a history of prior lumbar surgery, or suspected cauda equina syndrome or a rapidly progressive neurologic deficit (the last two need emergency, not routine, imaging).[5]
Treatment Targets
- Acute low back pain: promote rapid functional recovery, encourage continued or early return to activity and work, and reduce pain-related distress and fear-avoidance behaviour.
- Subacute or recurrent low back pain: prevent progression to chronic pain and disability through timely reassessment, and prevent or minimize prolonged work absence.
- Chronic low back pain: restore function, fitness, and role participation (including work) by addressing both the physical and psychological contributors to persistent pain, rather than pursuing complete pain resolution as the primary endpoint.
- At every stage: identify and act on red flags promptly, avoid unnecessary imaging and over-medicalization, and minimize long-term opioid exposure.
Choose Initial Treatment
Every patient, every stage
1st line, every patient Educate and reassure about the generally favourable natural history of low back pain, and encourage staying active and continuing or resuming normal activity and work as soon as tolerated.[1]
Avoid prescribed bed rest for uncomplicated low back pain -- it does not speed recovery, results in a longer duration of pain and sick leave than staying active, and should not be used even as a short bridging measure.
Acute low back pain (under 4 weeks)
1st line nonpharmacologic measures -- superficial heat, staying active, and spinal manipulative therapy where available -- before adding a scheduled medication.[1]
1st-line pharmacologic option, if still needed a scheduled oral NSAID (e.g., naproxen or ibuprofen); no NSAID or COX-2 inhibitor has been shown more effective than another for back pain specifically, so select by the patient’s GI/cardiovascular risk and tolerability rather than by habit.
Add only if the NSAID alone is inadequate, and only for a short course (no more than 1-2 weeks) a muscle relaxant (e.g., cyclobenzaprine); evidence for benefit is limited and inconsistent, and adding one to an NSAID increases sedation, dizziness, and dry mouth without clearly improving pain or function over the NSAID alone.
Alternative when an NSAID is contraindicated or not tolerated acetaminophen (e.g., 500 mg PO every 4 hours); current evidence does not show a meaningful benefit over placebo for back pain specifically, but its comparatively favourable safety profile still makes a trial reasonable when an NSAID cannot be used.[6]
Avoid as a routine first-line choice opioids -- early opioid use has not been shown to improve disability outcomes and is associated with worse long-term function; reserve for severe pain not responding to the measures above, at the lowest effective dose, for no more than 3 to 5 days before a mandatory review.[7][8]
Subacute or recurrent low back pain (4-12 weeks)
If pain and work absence have not resolved by 1 month, escalate to active, coordinated management: individual patient education, a workplace visit if feasible, and a planned, timelined return-to-work or return-to-function target -- this combination outperforms clinic-based treatment alone for restoring function and minimizing work loss.
Screen explicitly for yellow flags (psychosocial risk factors for chronicity) at this stage, and address them directly rather than continuing to treat only the physical complaint.
Chronic low back pain (over 12 weeks)
1st line a combination of 2 or more nonpharmacologic modalities -- active exercise, multidisciplinary rehabilitation, and cognitive behavioural therapy or another psychosocial intervention -- conducted where possible in the context of workplace re-entry.[1]
Pharmacologic adjunct a trial of an NSAID, since some evidence supports NSAIDs -- unlike most other drug classes -- for chronic low back pain specifically.
Special situation -- comorbid depression/anxiety or centralized/widespread pain features duloxetine; it is the only antidepressant with a specific chronic low back pain indication, though its exact place in therapy is not firmly established, and it will not necessarily improve the pain itself if the underlying driver is an untreated mood disorder alone.
Avoid as routine therapy; special situation only opioids -- reserve for a patient in whom a full trial of non-opioid pharmacotherapy and a nonpharmacologic program has failed, who has no contraindication (active depression, anxiety, PTSD, or a substance use disorder). Start below 50 mg morphine-equivalent/day, keep the initial course to 3-5 days before review, agree on a tapering strategy before starting, and never exceed 90 mg morphine-equivalent/day.[8]
Non-Pharmacologic Treatment
- Patient education and reassurance about the self-limiting nature of most low back pain -- this alone reduces distress and improves outcomes, and should be delivered explicitly, not assumed to happen by default.
- Encourage staying active and continuing or resuming work and normal activity as soon as tolerated; avoid unnecessary bed rest, and avoid premature physical therapy referral for straightforward acute pain that has not yet been given a chance to improve on its own.
- Superficial heat for acute low back pain.
- Spinal manipulative therapy has a modest effect on pain and disability in acute low back pain, and is most effective when combined with another modality (e.g., exercise, a psychological intervention) rather than used alone.[9]
- Structured exercise therapy is beneficial at every stage. Core/motor-control exercise programs and supervised walking programs (building toward 30 minutes of brisk walking 5 days a week, with a pedometer and walking diary) are both reasonable, evidence-supported options, particularly for chronic low back pain.
- For subacute or chronic low back pain with work absence: a coordinated, workplace-integrated return-to-work program with a defined treatment timeline -- the workplace intervention itself, not the specific clinic treatment modality chosen, is what most reliably drives successful return to work.
- For chronic low back pain: combine 2 or more nonpharmacologic modalities -- multidisciplinary rehabilitation, cognitive behavioural therapy, relaxation therapy, and mindfulness-based stress reduction all have supporting evidence, especially in combination and when integrated with workplace re-entry planning.
- Evidence is weak, contradictory, or insufficient for several other commonly used modalities: acupuncture, yoga, therapeutic ultrasound, transcutaneous electrical nerve stimulation (TENS), lumbar supports, insoles, and prolotherapy. These are not routinely recommended, though an individual trial alongside evidence-based care is reasonable if a patient wants to pursue one.
- Interventional/procedural options exist for refractory chronic low back pain but require specialist referral and have inconsistent evidence: trigger point injections, epidural steroid injections, and facet joint injections have not shown consistent benefit for pain or work disability, though some patients report improvement with only minor side effects; image-guided radiofrequency facet rhizotomy can be considered for intractable facet-mediated pain.
Special Populations
Pregnancy
Over half of pregnant patients experience low back pain, usually lumbar or sacroiliac, driven by hormonal changes, anterior displacement of the centre of gravity, and weight gain -- prior low back pain and being overweight both increase the likelihood. Nonpharmacologic measures remain first-line: a program of walking and modified exercise to strengthen abdominal and back muscles, adapted to the stage of pregnancy. TENS can be used over a limb but not over the low back or abdomen, given a theoretical risk of precipitating labour.
Acetaminophen at therapeutic doses is an appropriate first choice for analgesia. Short-term NSAID use may be considered in the 1st or 2nd trimester, but NSAIDs should be avoided in the 3rd trimester given the risk of premature closure of the fetal ductus arteriosus and neonatal pulmonary hypertension, and use from around 20 weeks onward carries a risk of reduced amniotic fluid (oligohydramnios) from fetal renal effects -- if NSAID treatment extends beyond 48 hours in this window, ultrasound monitoring of amniotic fluid is reasonable, and NSAIDs should be stopped if oligohydramnios is detected. Avoid a topical diclofenac product formulated in a DMSO vehicle, since the vehicle’s safety in pregnancy is unknown.
Avoid opioids where possible; if truly needed, use the lowest effective dose for the shortest possible time -- high doses and use near term can cause neonatal opioid withdrawal and respiratory depression. If a patient is on chronic opioid therapy, begin weaning in the 2nd trimester where feasible, reducing by no more than 10% of the total dose per week, slowing to roughly 5% per week for the final 30% of the taper.[8] Avoid muscle relaxants (cyclobenzaprine, methocarbamol, orphenadrine, baclofen) given insufficient safety data in pregnancy; diazepam specifically carries a possible congenital malformation risk and, with extended use, a risk of neonatal withdrawal and floppy infant syndrome. Gabapentinoid safety data in pregnancy are insufficient. Tricyclic antidepressants are considered relatively safe in pregnancy but should not be started specifically to treat chronic low back pain, since efficacy evidence for that indication is lacking.
Breastfeeding
Acetaminophen at therapeutic doses is appropriate. Ibuprofen has been used safely during breastfeeding, and short-term use of most other NSAIDs is generally considered compatible -- prefer a shorter-half-life agent where possible. Opioid transfer into breast milk is generally small, but given the seriousness of opioid toxicity, limit use to 2-3 days and counsel on toxicity signs in both mother (oversedation, constipation) and infant (drowsiness, poor feeding, breathing difficulty); stop breastfeeding if either develops signs of toxicity. Avoid codeine during breastfeeding given the (debated but still standing) concern for rare, serious neonatal toxicity in ultra-rapid CYP2D6 metabolizers. Tramadol has a long half-life in newborns and limited infant outcome data -- use cautiously if at all. Diazepam accumulates in the breastfed infant and should be avoided; gabapentin produces low infant serum levels with no reported adverse effects at typical maternal doses.
Pediatrics
This chapter addresses adult mechanical low back pain. Low back pain in a child or adolescent is much less common than in an adult and is more likely to have an identifiable structural or systemic cause -- it should prompt a lower threshold for further assessment and referral rather than being managed with the same adult mechanical-low-back-pain algorithm, and pediatric-specific dosing for the drugs in this chapter is not established here.
Older adults
Diazepam and the other muscle relaxants in this chapter (cyclobenzaprine, methocarbamol, orphenadrine, tizanidine, baclofen) are not recommended in patients over 65 given increased sedation, fall risk, and (for diazepam) accumulation risk. NSAIDs carry a higher GI, renal, and cardiovascular risk in this population -- prefer a topical NSAID or acetaminophen trial first, and use the lowest effective oral NSAID dose for the shortest duration if one is needed. Start any opioid at a lower dose with closer monitoring.
Renal and hepatic impairment
Avoid NSAIDs, including a topical NSAID used over a large area or for a prolonged period, in significant renal impairment. Duloxetine is contraindicated at ClCr under 30 mL/min. Baclofen and gabapentin both require renal dose adjustment. Acetaminophen requires a lower total daily dose and closer monitoring in significant hepatic impairment; baclofen has a rare hepatotoxicity risk requiring caution in hepatic disease.
Monitoring & Follow-Up
- Acute low back pain: reassess within 1-4 weeks if symptoms are not clearly improving, or sooner if a new red flag develops. Track return to function and activity/work, not pain score alone, as the primary marker of progress.
- Subacute low back pain: reassess at 4-6 weeks if pain or work absence has not resolved -- this is the trigger point to screen (or re-screen) for yellow flags and escalate to active, coordinated management.
- Chronic low back pain: scheduled follow-up with explicit functional goals (not only pain intensity) tracked at each visit.
- Whenever an opioid is prescribed: confirm an agreed tapering strategy was documented before starting, reassess the ongoing need and morphine-equivalent dose at every refill, and do not exceed 90 mg morphine-equivalent/day.[8]
- Chronic high-dose acetaminophen or duloxetine use: periodic liver function monitoring.
- Long-term NSAID use: periodic renal function and blood pressure monitoring, and GI risk reassessment.
Common Errors to Avoid
- Prescribing bed rest for uncomplicated low back pain -- it worsens, not improves, outcomes.
- Ordering imaging without a red flag or a specific therapeutic-planning indication -- imaging findings are common in people without any back pain, correlate poorly with symptoms, and are associated with a higher likelihood of unnecessary surgery.[4]
- Reflexively combining an NSAID with a muscle relaxant, acetaminophen, and/or an opioid -- trial evidence shows this combination increases adverse effects (dizziness, drowsiness, dyspepsia, nausea) without improving pain or function over the NSAID alone.
- Assuming acetaminophen provides meaningful analgesic benefit for low back pain specifically -- current evidence does not support this; it is chosen for safety, not superior effectiveness.[6]
- Continuing a muscle relaxant beyond a short course, or using one routinely in a patient over 65.
- Starting an opioid as first-line therapy, or continuing one beyond 3-5 days for acute pain without a documented review and tapering discussion.
- Anchoring on "just back pain" and missing a cauda equina red flag -- urinary retention, saddle numbness, or new bowel/sexual dysfunction always needs same-day emergency assessment, not a trial of conservative therapy first.
- Failing to screen for yellow flags (psychosocial risk factors for chronicity) once symptoms or work absence pass the 4-week mark.
- Managing chronic low back pain with medication alone, without a coordinated nonpharmacologic and, where indicated, workplace-integrated plan.
- Using a sustained-release opioid formulation for intermittent, activity-related pain -- these are not shown to be more effective or safer than an immediate-release formulation for this pattern of pain.
- Missing CYP2D6-related codeine treatment failure, or the (debated but still standing) breastfeeding caution around codeine, in a patient or nursing parent for whom it was prescribed.
Clinical Decision Algorithm
Drug Tables
How to use this table: doses are adult doses for mechanical low back pain and require patient-specific confirmation, including renal/hepatic adjustment. This chapter does not establish pediatric dosing -- see Special Populations. Select any drug name to open its complete Pharmasist Drug Database page.
Nonopioid analgesics
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Acetaminophen | Adults: 325-650 mg PO Q4H PRN or scheduled | Hepatotoxicity with chronic high-dose or acute overdose use | Evidence does not support meaningful efficacy for low back pain specifically -- chosen for its comparative safety over an NSAID, not superior effectiveness. Total intake from all sources must not exceed 4 g/day. |
NSAIDs, oral
No NSAID or COX-2 inhibitor has been shown more effective than another for back pain specifically -- select by GI/cardiovascular risk and tolerability. Avoid in severe renal impairment.
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Ibuprofen | Adults: 400-600 mg PO Q6-8H Maximum: 2400 mg/day | GI toxicity, cardiovascular risk, nephrotoxicity | Doses of 2400 mg/day or more carry increased stroke/cardiovascular event risk -- avoid at this dose with cardiovascular disease or risk factors. |
| Naproxen | Adults: 500-1000 mg/day PO divided Q8-12H Sustained-release alternative: 750 mg PO once daily | GI toxicity, cardiovascular risk, nephrotoxicity | A reasonable default oral NSAID given a comparatively favourable cardiovascular profile among nonselective NSAIDs. |
| Naproxen sodium | Nonprescription strength: 220 mg PO Q8-12H Prescription strength: 825-1375 mg/day PO divided Q6-12H | GI toxicity, cardiovascular risk, nephrotoxicity | Same active drug as naproxen above in a different salt/strength labelling. |
| Celecoxib | Adults: 100 mg PO BID or 200 mg PO once daily | GI toxicity (less than nonselective NSAIDs), cardiovascular risk (not lower than nonselective agents), nephrotoxicity | Contraindicated with sulfonamide allergy, though cross-reactivity is uncommon. Avoid in ischemic heart disease, cerebrovascular disease, or heart failure. |
| Meloxicam | Adults: 7.5-15 mg PO once daily | GI toxicity, cardiovascular risk, nephrotoxicity | Once-daily dosing may support adherence; cardiovascular/GI risk profile is comparable to other nonselective NSAIDs at equivalent anti-inflammatory dose. |
NSAIDs, topical
Minimal systemic absorption -- a reasonable option to reduce systemic NSAID exposure, particularly with GI or renal risk factors.
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Diclofenac diethylamine 1.16%/2.32% gel | Adults: Apply to the affected area 3-4 times daily | Local skin irritation or dryness; hypersensitivity; systemic GI toxicity not seen in trials to date | For external use only. Available without a prescription. |
Muscle relaxants
Evidence for benefit in acute low back pain is limited and contradictory; adequate evidence is lacking for chronic low back pain. Short-course use only (no more than 1-2 weeks). Not recommended in patients over 65. Avoid in pregnancy (insufficient safety data).
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Cyclobenzaprine | Adults: 5-10 mg PO TID, or as a single bedtime dose | Drowsiness, dry mouth, dizziness, fatigue, nausea, constipation | Structurally similar to tricyclic antidepressants. Can be given as a single nighttime dose. Do not use with an MAOI. |
| Methocarbamol | Initial (first 48-72h): Up to 1500 mg PO QID Maintenance: 750-1500 mg PO TID-QID | Drowsiness, dizziness, headache, nausea, GI upset, harmless brown/black/green urine discolouration | Also available in combination with a nonprescription analgesic. |
| Orphenadrine | Adults: 100 mg PO BID (sustained-release) | Dry mouth, blurred vision, drowsiness, constipation, tachycardia; overdose can be life-threatening (anticholinergic toxicity, arrhythmia, seizures) | Can be given as a single nighttime dose. Significant anticholinergic burden -- avoid with other anticholinergic drugs where possible. |
| Baclofen | Initial: 5 mg PO TID Maximum: 20 mg PO TID | Sedation, muscle weakness, nausea, dizziness; rare hepatotoxicity | Adjust dose gradually to minimize adverse effects or withdrawal symptoms on discontinuation. |
| Tizanidine | Initial: 2 mg PO BID Maximum: 4 mg PO TID | Sedation, dizziness, dry mouth, weakness, hypotension, hepatotoxicity (monitor LFTs) | Adjust dose gradually to minimize adverse effects or withdrawal symptoms (e.g., rebound hypertension) on discontinuation. |
Benzodiazepine (short-term muscle relaxant use)
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Diazepam | Adults: 2-5 mg PO BID-QID, short course | Drowsiness, cognitive impairment, dependence with continued use, falls, accumulation in hepatic/renal impairment and in older adults | Short-term use only for acute pain. Not recommended in the elderly. Potentiates opioid and alcohol CNS depression. |
GABA derivatives (limited evidence, not a Health Canada-approved indication for low back pain)
Clinical experience only, no quality trial evidence -- may be considered for chronic low back pain with pain/tenderness across multiple sites.
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Gabapentin | Initial: 300-400 mg/day PO in 3 divided doses Maximum: 3600 mg/day PO in 3 divided doses | Sedation, ataxia, tremor, peripheral edema, GI upset, vision changes | Taper over at least 1 week to discontinue -- do not stop abruptly. Aluminum/magnesium antacids reduce absorption. |
| Pregabalin | Initial: 50-150 mg/day PO in 2 divided doses Maximum: 600 mg/day PO in 2 divided doses | Sedation, ataxia, edema, diplopia, weight gain, dry mouth | BID dosing is an advantage over gabapentin's TID regimen. |
Serotonin-norepinephrine reuptake inhibitor
The only antidepressant with a specific chronic low back pain indication; place in therapy not firmly established.
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Duloxetine | Initial: 30 mg PO once daily Maximum: 120 mg/day PO divided BID | Nausea, headache, drowsiness, insomnia, dizziness, dry mouth; avoid at ClCr under 30 mL/min | May help with pain associated with central sensitization (e.g., fibromyalgia-like or myofascial features). Risk of serotonin syndrome with an MAOI, tramadol, or another serotonergic drug. |
Opioids
Avoid as routine therapy at every stage. Reserve for severe pain unresponsive to the measures above, at the lowest effective dose, for the shortest duration, with an agreed tapering strategy in place before starting and a hard ceiling of 90 mg morphine-equivalent/day.
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Acetaminophen/codeine | Adults: 1-2 tablets PO QID PRN Maximum acetaminophen, all sources: 4 g/day | Nausea, vomiting, constipation, sedation, urinary retention, misuse potential | A significant minority of patients get little analgesic benefit from codeine because of CYP2D6 variability. Maximum recommended chronic non-cancer pain dose: under 90 mg morphine-equivalent/day; consider a stimulant laxative. |
| Tramadol | Controlled-release, initial: 100 mg PO once daily, titrate weekly Controlled-release, maximum: 300-400 mg/day depending on product | Respiratory depression, sedation, ataxia, constipation, seizures, nausea, orthostatic hypotension, serotonin syndrome risk | Do not use within 14 days of an MAOI. Caution with drugs that lower seizure threshold or are serotonergic (SSRI, TCA, bupropion). |
| Tramadol/acetaminophen | Adults: 1-2 tablets PO Q4-6H PRN Maximum: 8 tablets/day | Same as tramadol above, plus acetaminophen-related hepatotoxicity risk at high cumulative dose | 37.5 mg tramadol / 325 mg acetaminophen per tablet. |
| Morphine, sustained-release | Initial: 15 mg PO Q12H (or per product, 20-30 mg once daily for a once-daily formulation) | Nausea, vomiting, constipation, sedation, urinary retention, misuse potential | Sustained-release formulations are not recommended for intermittent, activity-related pain and are not shown more effective or safer than immediate-release for that pattern. |
| Hydromorphone, sustained-release | Initial: 3 mg PO Q12H, or per product 4 mg PO once daily | Nausea, vomiting, constipation, sedation, urinary retention, misuse potential | Preferable to titrate first with a shorter-acting product, then convert to the sustained-release dose once the effective total daily dose is known. |
| Oxycodone, sustained-release | Initial: 10 mg PO Q12H | Nausea, vomiting, constipation, sedation, urinary retention, misuse potential | Sustained-release formulations are not recommended for intermittent, activity-related pain. |
| Oxycodone/naloxone, controlled-release | Initial: 5 mg oxycodone/2.5 mg naloxone PO Q12H Maximum: 60 mg oxycodone/day | Same as oxycodone above; naloxone component reduces opioid-induced constipation; severe withdrawal if given rectally | Single doses should not exceed 40 mg oxycodone/20 mg naloxone -- supplement with a single-entity sustained-release oxycodone product if a higher total dose is needed. |
| Fentanyl, transdermal | Initial: 12-25 mcg/h patch, per conversion from prior opioid dose | Nausea, vomiting, constipation, sedation, urinary retention; less constipation but more sweating than other opioids | Contraindicated in opioid-naive patients -- only for a patient already tolerant on at least 60 mg/day oral morphine-equivalent. Change patch every 72 hours. Have patients return used patches to the pharmacy. |
| Buprenorphine, transdermal | Initial (may be used in opioid-naive patients): 5 mcg/h patch, applied once weekly | Application-site skin reaction, constipation, nausea, confusion in older adults | Has partial agonist/antagonist activity. Well tolerated in older adults and renal impairment. Do not use under 40 kg body weight. Risk of discontinuation syndrome on stopping. |
| Tapentadol, extended-release | Initial: 50 mg PO Q12H, may increase every 3 days | Nausea, vomiting, constipation, sedation, urinary retention, dizziness | Dual mechanism: mu-opioid agonist and norepinephrine reuptake inhibitor. |
References
- Noninvasive Treatments for Acute, Subacute, and Chronic Low Back Pain: A Clinical Practice Guideline From the American College of Physicians — Annals of Internal Medicine, American College of Physicians Clinical Guidelines Committee (Qaseem A, Wilt TJ, McLean RM, Forciea MA). Ann Intern Med 2017;166(7):514-530
- Red Flags for Low Back Pain Are Not Always Really Red: A Prospective Evaluation of the Clinical Utility of Commonly Used Screening Questions for Low Back Pain — Journal of Bone and Joint Surgery, American Volume (Premkumar A, Godfrey W, Gottschalk MB, et al.). J Bone Joint Surg Am 2018;100(5):368-374
- A systematic review identifies five "red flags" to screen for vertebral fracture in patients with low back pain — Journal of Clinical Epidemiology (Henschke N, Maher CG, Refshauge KM). J Clin Epidemiol 2008;61(2):110-118
- Spine: imaging for low back pain — Choosing Wisely Canada. Choosing Wisely Canada, Spine recommendations
- ACR Appropriateness Criteria Low Back Pain: 2021 Update — Journal of the American College of Radiology, Expert Panel on Neurological Imaging (Hutchins TA, Peckham M, Shah LM, et al.). J Am Coll Radiol 2021;18(11 Suppl):S361-S379
- Efficacy and safety of paracetamol for spinal pain and osteoarthritis: systematic review and meta-analysis of randomised placebo controlled trials — BMJ (Machado GC, Maher CG, Ferreira PH, et al.). BMJ 2015;350:h1225
- Low back pain and sciatica in over 16s: assessment and management — National Institute for Health and Care Excellence (NICE). NICE Guideline NG59, last updated 29 July 2026
- Guideline for opioid therapy and chronic noncancer pain — Canadian Medical Association Journal (Busse JW, Craigie S, Juurlink DN, et al.). CMAJ 2017;189(18):E659-E666
- Association of Spinal Manipulative Therapy With Clinical Benefit and Harm for Acute Low Back Pain: Systematic Review and Meta-analysis — JAMA (Paige NM, Miake-Lye IM, Booth MS, et al.). JAMA 2017;317(14):1451-1460
Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.