Clinical Trials On THC And CBD In Relieving Pain Suffered By Cancer Patients

Clinical Trials On THC And CBD In Relieving Pain Suffered By Cancer Patients

Pain associated with cancer can be very unpleasant. Opioids and anti-inflammatory medications given as first-line drugs in the treatment of pain in oncological patients do not always give satisfactory results.

In traditional medicine, cannabis preparations have been used for thousands of years to treat diseases or relieve symptoms that accompany them, but their effectiveness in specific indications is constantly being studied.

How cannabis helps cancer patients

To date, positive results have shown that cannabis reduces nausea and vomiting suffered by cancer patients undergoing chemotherapy. Cannabis is also used to stimulate appetite usually associated with oncological patients.

Most importantly, it is the pain-relieving effect that is the most frequently mentioned reason for the medical use of cannabis in treating cancer patients.

The analgesic effect of cannabinoids is linked to the cannabinoid receptors and the endocannabinoid system. Research studies carried out so far has shown that (cannabinoid receptors and endocannabinoid system) plays a significant role in relieving the pain of various types, including somatic, visceral or neuropathic pain.

An interesting fact is that non-steroidal anti-inflammatory drugs (NSAIDs), paracetamol or opioids increase the activity of the endocannabinoid system.

The analgesic effect of cannabinoids

There are many preclinical trials (on an animal model) regarding the analgesic effect of cannabinoids, mainly tetrahydrocannabinol (THC), which is the active ingredient of dronabinol or a combination of THC and cannabidiol (CBD) in Sativex. The results of these experiments confirm the analgesic effect of these compounds in relieving the pain associated with neoplastic disease without serious side effects.

Sativex is said to help relieve spasticity associated with multiple sclerosis.

Sativex from GW Pharmaceuticals is an oromucosal spray (medication) administered to the oral mucosa. It contains THC and CBD in an equal ratio of 1: 1. It turns out that just the ratio of the two cannabinoids is optimal for analgesia.

Clinical trial 1

117 adult cancer patients

Three groups (60, 58 and 59)

This is evidenced by the results of a 2010 clinical trial in which 117 adult patients were in the final stage of cancer. The study included patients who had used the highest tolerated doses of strong opioids for at least a week and still was under an intense pain ≥4.

On a 0-10 scale (visual-analog scale [VAS] above 4 is moderate pain and anything above the value of 10 is considered unbearable pain).

Participants of the study were randomly divided into three groups. The first group of 60 people received Sativex (2.7 mg THC and 2.5 mg CBD for one spray), 58 patients from the second group took THC as a spray (2.7 mg THC on start-up), and the third group of 59 people received placebo in the spray.

In the first week, the dose was adjusted in patients based on tolerability and achieving the desired analgesic effect. The maximum allowable dose was 8 sprays in 3 hours (at intervals of at least 15 minutes between two doses) or at most 48 sprays in 24 hours (130 mg THC and 120 mg CBD).

The percentage of “respondents” (patients who had a ≥ 30% reduction in pain intensity on a 0-10 scale, which was considered clinically significant).

  • In the Sativex group was 43%.
  • In the THC group, the respondent percentage was 23%.
  • In the placebo group – 21%.

Regarding side effects, in the Sativex 10/60 group, patients discontinued treatment due to side effects; in the second group, the percentage was 7/58 patients, and in the placebo group, 3/59 of patients discontinued treatment due to adverse reactions.

The most commonly reported side effects were drowsiness, nausea, vomiting and dry mouth.

Clinical trial 2

Another clinical trial conducted in 2013 shows that 15/39 participants were treated with Sativex for less than 2 weeks; others gradually withdrew from treatment within 1 year due to side effects (23/39), loss of effectiveness (3/39) and other causes.

The study showed that long-term use of Sativex is generally well tolerated without any loss of efficiency in relieving pain due to long-term use. In addition, patients who continued to use Sativex did not seek to increase the dose of the oromucosal spray, suggesting that cannabinoids may be useful in the treatment of cancer-related pain.

Clinical trial 3

So it was left to determine the optimal dosage. Therefore, patients in the 2012 study were randomly assigned to groups receiving three different doses of Sativex: group 1 received 4 atomic sprays daily (10.8 mg THC, 10 mg CBD), another group used 10 sprays per day (27 mg) THC, 25 mg CBD) and group 3 received 16 sprays per day (43 mg THC, 40 mg CBD). During the first 7 days the dose was gradually increased (from 1 to 4, 10 or 16), and then it was optimized for the next 2 weeks. On day 21-35 a proper examination took place.

The results showed that with increasing dose, several patients discontinued treatment due to side effects: 3/91 placebo, 5/91 for the lowest dose, 6/88 for the average dose, and 20/90 for the highest dose. Adverse effects of cannabinoids primarily concerned their effect on the central nervous system (CNS) and were associated with psychomotor dysfunctions, short-term memory impairment and toxic effects (poisoning).


In conclusion, cannabinoids may be promising compounds for pain relief in oncological patients who do not respond to conventional therapy. The results of the study show that THC alone may not be effective enough to achieve a good analgesic effect. This means that tetrahydrocannabinol should be combined with CBD to achieve the desired results.

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