Chemotherapy is maybe one of the most common treatments for cancer. It is often used in conjunction with other therapies, such as surgery. The main target is to cure, or at least to diminish the symptoms by reducing the size of the tumour or by stopping the spread of cancer cells around the body, lamentably it comes with unpleasant side effects, such as nausea and vomiting (also known as emesis).
It is estimated that around 50% of these patients will experience nausea or vomiting due to either the disease itself, or the anticancer drugs. Moreover, patients were found to experience the same bad feelings prior to a chemotherapy doses, also called anticipatory CINV, attributed to a psychological etiology. There are already a large number of anti-nausea and anti-emetic pharmaceutical medications that intend to control the problem, however, sometimes they are not strong enough, therefore alternatives are necessary. This article will discuss the current prescription available for CINV, as well as reviewing the benefits of the cannabinoids options.
Antineoplastic agents work by attacking fast-growing cells, both cancer and healthy ones. Normal tissues can be the hair follicles (causing hair loss), cells lining the mouth, stomach, and intestines. In general, people frequently delay or refuse further dosage, for the fear of facing CINV.
Current treatments regimens
During chemotherapy serotonin is released within the gastrointestinal tract. This serotonin can then join itself to 5-HT3 receptors (located in the peripheral and central nervous systems) and is known to be one of the causes of nausea and vomiting.
Classical management involves 5-HT3 receptor antagonists, which inhibit the binding itself. This form of antiemetic has proven to be very successful but it does not work for everyone and in some cases, can produce some adverse effects such as insomnia, nausea and dizziness. For that reason researchers have begun investigating cannabinoids.
To date, in the USA two forms of synthetic cannabinoids, dronabinol and nabilone, have been approved for CINV. Both are artificially manufactured variations of tetrahydrocannabinol (one of the active components that is naturally produced within the cannabis plant). These are usually given to the patient in case he has not responded to the conventional medication.
Cannabinoids, such as tetrahydrocannabinol (THC) and Cannabidiol (CBD), have been known to supress nausea and vomiting, in fact one of the first documented medicinal uses of THC was for CINV (1970’s). Since this conclusion, more and more studies has been carried out to find out if the cannabinoids mechanisms or the endocannabinoid system may have any influence over the sickness. When a cannabinoid is administered into the human body, it binds to its receptor (member of the endocannabinoid system), labelled as cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2), among others. These receptors are in the central nervous system, the immune system, the gastrointestinal tract and also within the emetic reflex pathway.
Therefore, it is understood that cannabinoids operate by inhibiting the interaction between serotonin and its receptor. An article published with animal models (vomiting was induced with CB1 receptor antagonist, cisplatin), revealed that THC was hugely effective in the reduction of emesis. These results mirrored those found in a similar study with humans. In addition, it was observed that the administration of CBD, in a dose dependent manner, also helped to decrease the reaction to cisplatin.
Cannabinoid treatment for CINV is still considered to be quite controversial, perhaps because many doctors are not well informed on its properties. However, for many it is the only hope when conventional solutions fail. THC and CBD do not only reduce any nausea or vomiting that comes from antineoplastic agents, but also increase the appetite, sleeping habits and pain relief. As more and more people opt for this kind of treatment, more research is being done to look into all the advantages of cannabinoids.