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SGEM#87: Let Your Back Bone Slide (Paracetamol for Low-Back Pain)

SGEM#87: Let Your Back Bone Slide (Paracetamol for Low-Back Pain)

Podcast Link: SGEM87

Date:  September 17th, 2014 

Guest Skeptic: Dr. Pal Ager-Wick is from Norway. Consultant at Legevakten in Drammen, which is a GP run ED handling most things except major trauma. Keen interest in everything evidence based especially ultrasound. Pal is bringing Matt and Mike from the Ultrasound podcast to Norway.

Case Scenario: 35 year old man presents to emergency department with mechanical back pain after doing some heavy lifting on the weekend. He has not “red flags”.

Question: Does paracetamol improve time to recovery from pain compared to placebo in patients with low-back pain?

Background: The leading cause of disability worldwide is low-back pain. Guidelines recommend paracetamol (acetaminophen) as the first-line agent. There have been no randomized control trials comparing paracetamol vs. placebo for low-back pain.


1) Cancer Related Red Flags with Low Back Pain

  • History of cancer
  • Unexplained weight loss >10 kg within 6 months
  • Age over 50 years or under 18 years old
  • Failure to improve with therapy
  • Pain persists for more than 4 to 6 weeks
  • Night pain or pain at rest

2) Infection Related Red Flags with Low Back Pain

  • Persistent fever
  • History of intravenous drug abuse
  • Severe Pain
  • Lumbar spine surgery within the last year
  • Recent bacterial infection
  • Immunocompromised states

3) Cauda Equina Syndrome Related Red Flags with Low Back Pain

  • Urinary Incontinence or retention
  • Saddle anesthesia
  • Anal sphincter tone decreased or Fecal Incontinence
  • Bilateral lower extremity weakness or numbness
  • Progressive neurologic deficit

4) Significant Herniated Nucleus Pulposus

  • Major Muscle Weakness (strength 3 of 5 or less)
  • Foot drop

5) Vertebral Fracture Related Red Flags with Low Back Pain

  • Prolonged use of Corticosteroids
  • Age greater than 70 years
  • History of Osteoporosis
  • Mild trauma over age 50 years (or with Osteoporosis)
  • Recent significant trauma at any age

6)  Abdominal Aortic Aneurysm Red Flags with Low Back Pain

  • Abdominal pulsating mass
  • Atherosclerotic vascular disease
  • Pain at rest or nocturnal pain
  • Age greater than 60 years

Reference: Williams CW et al. Efficacy of paracetamol for acute low-back pain:
a double-blind, randomized controlled trial. Lancet July 24, 2014

  • Population: 1,652 patients from Australia and New Zealand
    • Inclusion: adults who sought care for low-back pain directly or in response to a community advertisement. New episode with pain between 12th rib and buttock. Shorter than 6 weeks duration with the month prior having no pain. No leg pain. Pain had to be of at least moderate intensity (measured by a evaluation tool)
    • Exclusions: Suspected serious spinal pathology, current use of full, regular does of analgesics, spinal surgery in last 6 months, contraindications to paracetamol, psychotropic drugs, pregnancy or planned to get pregnant.
  • Intervention: Paracetamol as needed and paracetamol as regimen
  • Comparison: Placebo
  • Outcome:
    • Primary Outcome: Time to pain free (VAS 0 or 1) maintained for 7 days
    • Secondary Outcomes: Pain intensity, disability, function, global rating of symptom change, sleep quality, and quality of life. Process measures consisted of adherence to drug (daily and at 4 weeks); concomitant treatment use and work absenteeism (at 4 and 12 weeks); adverse events (at 1, 2, 4, and 12 weeks); and treatment satisfaction and patient masking (at 12 weeks).

Authors’ Conclusions: Our findings suggest that regular or as-needed dosing with paracetamol does not affect recovery time compared with placebo in low-back pain, and question the universal endorsement of paracetamol in this patient group.

checklist-cartoonQuality Check List for Random Control Trials:

  1. The study population included or focused on those in the emergency department? No
    • 235 primary care clinicians (181 general practitioners, 50 pharmacists, and four physiotherapists) across Sydney, Australia, screened consecutive patients who sought care for low-back pain directly or in response to a community advertisement
  2. The patients were adequately randomized? YES
  3. The randomization process was concealed? YES
  4. The patients were analyzed in the groups to which they were randomized? YES
  5. The study patients were recruited consecutively (i.e. no selection bias)? YES
  6. The patients in both groups were similar with respect to prognostic factors? YES
  7. All participants (patients, clinicians, outcome assessors) were unaware of group allocation? YES
  8. All groups were treated equally except for the intervention? YES
  9. Follow-up was complete (i.e. at least 80% for both groups)? YES
  10. All patient-important outcomes were considered? YES
  11. The treatment effect was large enough and precise enough to be clinically significant? No

Key Results: They had over 1,600 patients enrolled in the study with 550 regular paracetamol group, 549 to the as-needed paracetamol group and 553 to the placebo group.

Was there a difference in their primary outcome of time to recovery from low-back pain? Just to remind everyone that was defined as self-reporting 0-1 on a pain VAS (pain free) for 7 days.

No difference in median time to recovery

  • Primary Outcome: There was no difference in median time to recovery between the three groups.
    • Regular 17 days (95%CI 14-19), As-needed 17 days (95% CI 15-20) and placebo 16 days (95% CI 14-20).
  • They also expressed this as a hazard ratio (HR):
    • Regular vs. Placebo HR 0.99 (95%CI; 0.87-1.14)
    • As-Needed vs. Placebo HR 1.05 (95% CI 0.92-1.19)
    • Regular vs. As-Needed HR 1.05 (95% CI; 0.92-1.20)
  • Secondary Outcomes: They looked at pain intensity, disability, function, global rating of symptom change, sleep quality, and quality of life, adherence to drug, concomitant treatment use and work absenteeism, adverse events, treatment satisfaction and patient masking.
    • There was no difference in secondary outcomes. Table 3 in the manuscript details the change in secondary outcomes. They did longitudinal mixed models and did not demonstrate any differences between groups for any of the secondary outcomes.

Screen Shot 2015-04-25 at 3.11.12 PM

This is a large and well designed study which aims to see if paracetamol is an efficacious treatment for uncomplicated lower back pain with no red flags. It is important to note that the time to self reported VAS 0-1 for one week was the primary outcomes. Both as needed and a regular dosing of paracetamol does not seem to make for a more speedy recovery.

It was a very well done study but I have some concerns that 1/3 of the patients approached declined to participate. There are also issues with external validity to the ED setting. Are people who mainly present to the General Practitioners office different from those that present to the ED in Australia and New Zealand?

In addition, how is low-back pain perceived in Australia and New Zealand? There can be differences perceptions, approaches, management between counties when it comes to various conditions. It would be interesting hear from someone down under. If you are a SGEM listener from Australia or New Zealand send me an email ( I would love to hear and share your thougths.

Naproxen was used as a rescue medication, and as this study was industry sponsored this study might later be used as support for naproxen as standard for lower back pain.

So you are not just a skeptic but you are also a cynic. But the drug company that sponsored this trial makes paracetamol so you would think the bias would be towards finding an effect?

Anybody who had read Ben Goldacre’s book Bad Pharma: How Drug Companies Mislead Doctors and Harm Patients would become cynical towards the pharmaceutical industry.

I think the lack of effect says more about the complex nature of low back pain in our society than the treatment. When there are multiple modalities all claiming to have great effect for the same condition I am skeptical that anything really works well (medical, manipulative, non-science based, etc).

I would interpret the data saying the natural history of acute low back pain with no underlying serious pathology is a self-limiting condition. We should not expect acetaminophen to effect time to recovery in this type of situation.

There is a strong placebo effect involved in the treatment of low back pain. If the placebo effect is large and the active treatment effect is small it may be hard to distinguish the signal (treatment) from the noise (placebo). Patients who believe in the treatment modality will more likely get benefit. So I think when it comes to treating non-serious low back pain, it all depends…

Comment on Authors’ Conclusion Compared to Our Conclusion: Agree with their conclusions based on the data presented and encourage being skeptical of the universal endorsement of paracetamol for these types of patients.

SGEM Bottom Line: It appears that paracetamol does not improve time to recovery compared to placebo for out-patients with low-back pain.

Clinical Application: This is just one randomized clinical trial looking into the issue and is not strong enough evidence for me to abandon recommending this treatment modality. I would like to see the study replicated in my practice environment. Specifically, a study looking at consecutive patients presenting to the emergency department with low-back pain.

Dr Pal Wick

Dr Pal Ager-Wick

What Do I Tell My Patient? You appear to have a mechanical injury to your low-back. There are no “red flags” to suggest anything more serious is going on right now. The natural history of this condition is for it to resolve with or without treatment. Has anything worked well for you in the past? Different treatments have different potential benefits and harms. Taking paracetamol has not been shown to speed up how fast you get better.  Most people get better within a few weeks. You should try to stay active and see your primary care doctor in a couple of weeks if the pain is not resolving. Please return to the emergency department if your pain is getting worse, you develop any of those red flags we discussed or are otherwise concerned.

Keener Kontest: Last weeks winner was Loice Swisher from Philadelphia. They knew the name of the ECG manifestation of pericarditis named after Dave Spodick? Spodick’s Sign is downward sloping of the TP segment is suggestive of pericarditis and reported to occur in as much as 80% of the patients.  It can be essentially the entire QRST segment and lead II has been reported to be usually the best lead to see this in.

Listen to the podcast to hear this weeks keener question. If you know the answer send an email to with “keener” in the subject line. The first person to correctly answer the question will receive a cool skeptical prize

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Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.