Evidence Base Research Area: Pain

A Multicenter Dose-Escalation Study of the Analgesic and Adverse Effects of an Oral Cannabis Extract (Cannador) for Postoperative Pain Management

Article: Holdcroft, Anita, Mervyn Maze, Caroline Dore, Susan Tebbs, and Simon Thompson. “A multicenter dose-escalation study of the analgesic and adverse effects of an oral cannabis extract (Cannador) for postoperative pain management.” Anesthesiology 104, no. 5 (2006): 1040-1046.


Pain, cannabis and cannabinoids are a complex topic of medical importance. Whilst the exact details of the analgesic mechanisms of cannabinoids and cannabis constituents are still elusive, there is a growing body of evidence pointing towards its use as a pain-relieving medication. In this multi-centre medical trial from 2006 based in the United Kingdom a standardized cannabis extract was tested for post-surgery pain management properties in a group of patients who would usually require overnight opiate-based pain relief (typically morphine).

Study design

The investigators administered a single fixed dose of the cannabis extract post-operation that consisted of three different dosage strengths of either 5mg, 10mg or 15mg THC-rich cannabis extract (capsules). They had a total of 65 patients taking the single fixed dose of cannabis extract with 11 patients taking 5mg, 30 patients taking 10mg and 24 patients taking 15mg (see Table 1.). Following this they measured various pain scores, adverse-effects and observed whether the patients needed to take any ‘rescue medication’ to relieve pain.

Main outcomes

Pain relief was positively associated with the increasing dosage of oral cannabis extract in this study which was inferred by measuring pain via verbal report along with the request for rescue medication by patients. For instance, rescue medication was requested by 11/11 (100%) of the patients in the 5mg THC-extract cohort, whereas 15/30 (50%) for the 10mg THC-extract group and 6/24 (25%) for the 15mg THC-extract group (see Table 2).

Adverse effects were also more frequently reported in the higher dosage groups, with one severe incidence of a patient fainting in the 15mg group that had an issue with blood-pressure, dizziness and tiredness, leading to a termination of recruiting more participants to the study. Other frequently reported side-effects included xerostomia (dry mouth) and psychological effects.

Another interesting insight provided by the authors was performing a ‘numbers needed to treat’ analysis (NNTs), which is an approximate calculation that works out the number of patients needed to treat to help one patient. For the 10mg group the NNT was 2 patients and for the 15mg it was 1.3 patients. As the authors of the study write “…These values are similar to the NNTs of commonly used orally administered drugs for moderate pain intensity such as morphine, paracetamol, and ibuprofen (McQuay & Moore 1998) and indicate a potential role for cannabinoids in postoperative pain management…”


Overall, this study provides good evidence of the pain-relieving properties of a THC-rich cannabis extract in a variety of patients undergoing different surgeries (breast, general, orthopaedic, gynaecological and plastic surgeries). Whilst the number of participants is small this gives a good starting point for clinicians looking to study the pain relieving properties of cannabis and cannabinoids and for those looking to expand upon the research. However, the diversity of patient types participating in the study does also make it harder to draw specific conclusions about the therapeutic activity of this particular THC-extract in a specific type of surgery. Further, it is unclear as to how the pre-surgery medical protocols might affect the cannabis medications and individual patient outcomes, especially considering individual differences and patient histories (Prior medication use, ECS genetics etc…).

Nonetheless it does demonstrate an increase in analgesic activity of a THC-extract as the dose increases from 5mg to 15mg. Although limited insight can be gathered as it was a single-fixed dose experiment, the next step is to investigate repeated dosing regimens in post-operative pain management and to look at how the administration of cannabis extracts influence treatment outcomes. Further it is important for researchers to investigate how drug-drug and drug-herb interactions may occur in clinical settings such as surgery.

In conclusion, this research provides a great deal of insight from a variety of medical centres in the UK about the analgesic properties of cannabis in a field of medicine that is becoming ever more important to manage as opioids are increasingly being utilized in medicine. It may be that cannabis and cannabinoids offer an effective alternative that is similar in efficacy to standard treatments.

Read the original study (you must be logged in to read study details)

Further investigation and research into cannabis use (both recreational and medical) is thoroughly encouraged by The Academy, particularly through the use of our own online coursesevidence base and whitepapers.

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