Pain Relief for Rats Using CBD Study and How It Might Apply to Humans

In 2017, researchers from the University of São Paulo looked at how CBD affected pain relief in rats by looking at different doses and delivery methods. In their study entitled “Cannabidiol Is a Potential Therapeutic for the Affective-Motivational Dimension of Incision Pain in Rats” the researchers found evidence that CBD provided significant results for pain relief compared to control groups. Interestingly, the dosage amount seemed to matter: too little and too much CBD didn’t yield significant pain relief.

In this article, we will look at the details of the study and what the results mean in terms of using CBD for pain relief in humans.

The Study

To get a picture of the study mentioned earlier, what they did was:¹

• Use a total of 275 rats in the test.
• They made a physical cut behind one of their hind paws and stitched it back up.
• After 24 hours, they used a probe that measured force and started poking the rat near where they made the physical cut (the wound).
• They observed when the rat lifted up its paw and visually flinched, then recorded the pressure to induce that response.
• They then injected CBD directly into the brain (a section called the rACC which people believe is responsible for feeling pain) as well as injecting it into the stomach (to simulate if you were to ingest CBD)
• Less pain was observed after a stomach injection (intraperitoneal) of 3 and 10 mg/kg
• Less pain was observed after a brain injection at a dosage of 10 to 40 nmol/0.25 μL

Study Results

The results for CBD stomach injection were as follows:

• The researchers observed the effect of CBD’s anti-pain properties for at least 150 minutes after the administration of 3mg/kg dose.
• Researchers also observed significant anti-pain effects 60 minutes after an injection of a 10 mg/kg dose.
• 3 mg/kg and 30 mg/kg had no significant response

The result from CBD injection into the brain was:

• CBD (40 nmol/0.25 μL) had a 120-minute effect

What Does This Mean for Humans?

Like any animal study, it’s difficult to extrapolate the results to apply them to humans. That being said, the biggest thing worth looking at is the amounts the rats were receiving and what the equivalent amount would need to be to elicit a similar response.

The effective results showed that in rats, the CBD dosages need to be:

• More than 3 mg/kg or 1.36 mg./lb.
• Less than 10 mg/kg or 4.55 mg./lb.

Where it wasn’t effective in rats was CBD dosages of:

• Less than 0.3 mg/kg or 0.14 mg/lb.
• More than 30 mg/kg or 13.63 mg/lb.

For an average American male who weighs 198 lbs.:

• An effective CBD dosage is between 269 mg and 900 mg.
• Non-effective CBD dosage is less than 27 mg and more than 2698 mg.

For an average American female who weighs 170 lbs. this translates to:

• An effective CBD dosage of between 231 mg and 774 mg.
• Non-effective CBD dosage of less than 24 mg and more than 2317 mg.

The study results suggest CBD doses in the recommended serving sizes found on the labels of CBD products may be inadequate. Keep in mind that in this study, they were looking at pain relief for a physical wound and not general aches and pains which most people are probably taking CBD for.

The Cost of CBD at Effective Dosages

It may give consumers some perspective in terms of cost if they were to take CBD dosages for pain relief similar to how it was done in the study.

If we were to rely on Charlotte’s Web 25 mg CBD Capsules as a reference point for cost:

• $269.99 for 90 ct (2250 mg CBD) – $0.12 per mg or $3 per capsule
• $179.99 for 60 ct (1500 mg CBD) – $0.12 per mg or $3 per capsule (no volume discount)
• $94.99 for 30 ct (750 mg CBD) – $0.13 per mg or $3.25 per capsule

To get the 3 mg/kg to 10 mg/kg effective dosage as concluded by the study, a 150 lb. person would need to take anywhere from 8 capsules to 27 capsules. Based on the cheapest price option, 8 capsules will cost $24 (3 mg/kg dose) and 27 capsules $81 (10 mg/kg dose).

Conclusion

It should be considered that the dosages previously mentioned are based on the rat study where each rat was surgically cut and then sewn back up. This is probably on the extreme side as most people aren’t using CBD strictly for pain but it makes it obvious that an effective dose of CBD is not cheap. This means for most products out there, we probably are underdosing based on this one study.

1. Genaro, K. et al. (2017 Jun 21). Cannabidiol Is a Potential Therapeutic for the Affective-Motivational Dimension of Incision Pain in Rats. Frontiers in Pharmacology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478794/.