First of all, it should be noted that neither CBD nor Kava are drugs of the pain relief type. They do, however, exhibit pain-relieving properties and CBD boasts a much broader palette here.
We have already mentioned CBD’s direct effect on TRPV1 receptors, which are responsible for pain sensation, among other things. TRPV1 is a vanilloid receptor, also known as a capsaicin receptor (a spicy substance known for feeling the spiciness of chilli peppers). Reducing the level of pain sensation is primarily an effect on the signal going to the brain. The activated receptor reduces the intensity of the signal.
The similarity in the effects of CBD and capsaicin also relates to anti-inflammatory properties. CBD effectively reduces inflammation by, among other things, acting on COX and LOX enzymes.
CBD also shows neuroprotective properties.
Kava Kava does not have such extensive capabilities in the context of pain relief. However, it is renowned for its muscle tension-reducing properties, making it invaluable in cases related to muscular pain, i.e. back pain or menstrual cramps.