Caffeine as an analgesic adjuvant for acute pain in adults
– Source: Cochrane Database of Systematic Reviews, Mar 2012
By Christopher J Derry, Sheena Derry, R Andrew Moore
[Note: Cochrane reviews are evaluations of medical research meant to support healthcare decisions based on the best current evidence. To read the full text pdf of this article, click HERE and select ‘read review.’ Or listen to an audio introduction/summary by selecting ‘play now.’ According to the audio, adding 100mg of caffeine – equivalent of a mug of coffee – gives good pain relief for 5% to 10% more people, and that percentage went up in studies testing doses of 200mg, etc. Reasons? Caffeine hastens analgesic absorption from the stomach but is also somehow analgesic in its own right. The article gives results for the different drug & caffeine combos tested.]
Background: Caffeine has been added to common analgesics such as paracetamol, ibuprofen, and aspirin, in the belief that it enhances analgesic efficacy. Evidence to support this belief is limited and often based on invalid comparisons.
Objectives: To assess the relative efficacy in acute pain of a single dose of any analgesic plus caffeine against the same dose of analgesic alone.
Search methods: We searched CENTRAL, MEDLINE, EMBASE, and the Oxford Pain Relief Database to January 2012, and also carried out Internet searches and contacted pharmaceutical companies known to have carried out trials that have not been published.
Selection criteria: We included randomized, double-blind studies that compared a single dose of analgesic plus caffeine with the same dose of the analgesic alone in the treatment of acute pain.
Data collection and analysis: Two review authors independently assessed eligibility and quality of studies, and extracted data. Any disagreements or uncertainties were settled by discussion with a third review author.
We sought any validated measure of analgesic efficacy, but particularly the number of:
• Participants experiencing at least 50% of the maximum possible pain relief over four to six hours,
• Participants reporting a global evaluation of treatment of very good or excellent,
• Or headache relief after two hours.
We pooled comparable data to look for a statistically significant difference, and calculated numbers needed to treat to benefit (NNT) with caffeine.
We also looked for any numerical superiority associated with the addition of caffeine, and information about any serious adverse events.
Main results: We identified 19 studies (7,238 participants) in valid comparisons. Most studies used paracetamol or ibuprofen, with 100 mg to 130 mg caffeine, and the most common pain conditions studied were postoperative dental pain, postpartum pain, and headache.
There was a small but statistically significant benefit with caffeine used at doses of 100 mg or more, which was not dependent on the pain condition or type of analgesic.
About 5% to 10% more participants achieve a good level of pain relief (at least 50% of the maximum) with the addition of caffeine, giving a NNT of about 15. [That is, taking caffeine with their analgesic would enable 1 more person in a group of 10 or 15 to reduce pain by 50% or better.]
Source: Cochrane Database of Systematic Reviews, Mar 2012. DOI: 10.1002/14651858.CD009281.pub2, by Derry CJ, Derry S, Moore RA. Pain Research and Nuffield Department of Clinical Neurosciences (Nuffield Division of Anaesthetics), University of Oxford; Pain Research Unit, Churchill Hospital, Oxford, UK. [Email: firstname.lastname@example.org]