Nausea, vomiting, and marijuana
Nausea and vomiting (“emesis”) are common symptoms with many different causes: central nervous system (brain and inner ear), peripheral nervous system (usually from the heart or gastrointestinal tract), mechanical (distension of the stomach and gut), metabolic (“food poisoning”), and pharmacological (from medications, especially from cancer chemotherapy). Usually nausea accompanies vomiting, but in some conditions such as bowel obstruction, vomiting may occur without nausea. Nausea and vomiting may be caused by factors as diverse as pregnancy, viral illnesses, heart attacks, gall bladder and bowel disease, increased intracranial pressure of brain masses, and radiation poisoning, even by psychological factors such as unpleasant odors or anticipation of receiving chemotherapy.
Nausea and vomiting result when the brainstem’s “vomiting center” is stimulated. The vomiting center receives input from many sources—from the nearby “chemoreceptor trigger zone” (CTZ), from the inner ear via the cerebellum, from the gastrointestinal tract via the vagus nerve, and from chemicals circulating in the blood stream. These inputs to the vomiting center involve many of the different chemical systems of the nervous system, so similarly there are many drugs available to treat nausea and vomiting. As a group we call these drugs “antiemetics.”
As one example, consider the nausea and vomiting that accompany motion sickness. In susceptible people, motion overstimulates the “vestibular apparatus” or “labyrinth” of the inner ear. There are H2 histamine receptors and “muscarinic” acetylcholine receptors in the inner ear. Expectedly, chemicals that block histamine (e.g., Dramamine™) and acetylcholine (e.g., the scopolamine in Transderm-Scop™ patches) can treat that inner ear type of nausea and vomiting.
When stomach distention and the slow emptying of the stomach is a cause of nausea, as with patients who suffer diabetic gastropathy (diabetic damage to the nerves that control stomach motility), drugs that improve stomach movement and emptying can be helpful. Reglan™ (generic: metoclopramide) is typical of such drugs.
Another example—consider the nausea and vomiting that accompany chemotherapy, “stomach flu,” or opiate use, vomiting that is caused by stimulation of the chemoreceptor trigger zone. The CTZ has D2 dopamine receptors and 5-HT3 serotonin receptors. Chemicals that block dopamine and serotonin can treat that CTZ type of nausea and vomiting. Phenothiazines are a class of drugs best known for treating certain psychiatric conditions, but, because they are dopamine blockers, are also used to treat nausea and vomiting. Phenothiazines have an added benefit of decreasing the contractions of the muscles in the lower esophagus that would otherwise aggravate nausea and vomiting. Phenergan™ (generic: Promethazine) is typical of these drugs. Unfortunately, phenothiazines’ anti-dopamine effects can also cause severe and uncontrollable Parkinsonism-like muscle spasms, an unwelcome effect that limits phenothiazine dosages, hence limits their usefulness.
Most of the nausea and vomiting from cancer and HIV chemotherapy drugs is due to the drugs’ stimulation of the CTZ. Because the nausea and vomiting can be so severe as to cause patients to abandon their treatment, the importance of controlling such nausea and vomiting cannot be overstated. A relatively new class of antiemetics blocks the CTZ’s 5-HT3 serotonin receptors. These 5-HT3 blockers are very effective in reducing the nausea and vomiting of chemotherapy. Typical of these is Zofran™ (generic: ondansetron)—very effective, very well tolerated, and very expensive. A typical monthly cost of Marinol (big Pharma’s patented version of THC) is $1,364. Research suggests that marijuana’s antiemetic effect is mediated through similar 5-HT3 blocking and some research suggests that a combination of marijuana with other 5-HT3 blockers is the most potent treatment of nausea and vomiting available today.
The newest class of antiemetics is the NK1 neurokinin blockers, also called “Substance P Antagonists.” Glaxo’s Emend™ (generic: aprepitant) is the first of these to be clinically available in the USA. Time will tell whether this class of drugs lives up to drug company claims.
Whether from chemotherapy or inflammatory bowel diseases like Crohn’s Disease, patients have long reported that marijuana was effective in controlling their nausea and vomiting. As early as the 1970’s researchers began to investigate those reports, but the Big-Pharma-funded research expectedly focused on their expensive patented drugs, rather than upon inexpensive natural marijuana. That said, there are plenty of studies supporting inexpensive natural marijuana as an antiemetic (see pages 3-9 in Amar MB, Cannabinoids in medicine: A review of their therapeutic potential, Journal of Ethnopharmacology 105 (2006) 1–25).
The federal government insists that marijuana must be a Schedule I drug because it has no medical use. With glaring hypocrisy, the same federal government allows prescription of Marinol™ (generic: dronabinol), a synthetic version of the natural cannabinoid delta9-THC. Heaping on yet another layer of hypocrisy, the same federal government that hates for anyone to “get high” allowed Big Pharma to patent and profit from THC, the most psychoactive of marijuana’s components. Amusingly, some oppositional researchers consider euphoria (feeling good) to be “toxicity.”
Politics aside, THC is an effective antiemetic, but, unmodulated by the benefits of CBD and other natural cannabinoids, single agent treatment with synthetic Pharmacological THC alone is often associated with lightheadedness, hallucinations and unpleasant frightened feelings. Larger scale studies also find that patients prefer natural marijuana. Natural delta8-THC and Big Pharma’s semisynthetic THC analogs, nabilone and levonantradol (neither of which are available to patients in the USA), are also effective antiemetics. For more detail I refer readers to Paul Armentano’s 2005 review of the literature comparing Marinol with natural marijuana.
Marijuana is also at a nexus of treatment of pain and vomiting. Because of opiate overstimulation of the CTZ (in past days, apomorphine was injected to induce vomiting to empty the stomach in drug overdose patients), nausea and vomiting are among the most common side effects of opiate narcotic treatment of pain. Many patients are unable to obtain sufficient pain relief from opiates, because opiate-induced nausea and vomiting prevents them from taking enough opiates to relieve their pain. Plain and simply, if you vomit up your painkillers, you get no pain relief. Here is where marijuana shines with double benefit, relieving nausea while also relieving pain.
Suffice it to say that marijuana is more effective and much better tolerated than the traditional antiemetics and equals or exceeds the newer antiemetics at a fraction of the cost. And, unlike the federal government, I do not begrudge you the “toxicity” of feeling good.
Be healthy, be happy, and be good.
Topic: Nausea and marijuana (Read 631 times)