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Ask Dr. Petro
Ask Dr. Petro
Dr. Denis J. Petro
By Denis Petro, MD
Consulting Neurologist. Chief of Neurology, Malcom Grow Medical, Andrews Air Force Base, VA. Director, Patients Out of Time.
These questions were submitted through the MS Patients Union email list. Dr. Petro has graciously agreed to answer questions concerning medical uses of cannabis with particular attention to neurologic indications as his busy schedule permits. He cannot of course diagnose or in general make drug recommendations, but he can field questions regarding cannabis and MS symptoms and other MS medications.
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Subject: Re: MSPU: Ideas and calls for action
Date: Friday, April 02, 2004 12:04 PM
Regarding the Miller discussion of the Lancet (CAMS Study) Cannabis article from November 2003, I have a number of thoughts.
Paul Armentano has written a brilliant rebuttal on the merits of Miller's article. Remember that different cannabis formulations have distinct properties. Cannabidiol is an important factor in the "anti-spasticity" action of any drug preparation. I read the Lancet article last November while traveling in Europe and personally thought that the point made by Paul regarding the composition of the administered preparation was key. Also, remember that the Cannabis treatment in the CAMS study seemed to have a "protective" effect on progression of underlying MS pathology in the Lancet study. This point was totally missed in the media reports of the study.
Regarding Dr. Miller, remember that he represents the NMMS and obviously is dependent on pharmaceutical industry financial support. If anyone wants to offer an opinion to the NMMS , both the National Multiple Sclerosis Society as well as the Multiple Sclerosis Association of America will be exhibitors at the annual meeting of the American Academy of Neurology to be held at the Moscone Convention Center, San Francisco on April 24 to May 1, 2004. It would be nice to see a number of concerned patients lobby these groups while the meeting is underway. (Exhibitors are open on Monday April 26 thru Thursday April 29) I'm sure Dr. Miller will be there.
Denis Petro, MD
Posted: April 6, 2004 by webmaster.
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Q: What is the mechanism of action of Cannabis?
That is, does the ingestion of Cannabis trigger the release of endogenous Cannabinoids that cause relief in the patient or does the release of endogenous Cannabinoids cause the release of yet other chemicals that actually cause the effects Cannabis is known for? -- Michael
A: Cannabis is a complex substance which includes a number of structurally related substances (cannabinoids). As many as 60 different cannabinoids have been characterized in native plant material. Since small changes in the chemical structure of a molecule can result in important differences in biologic action, individual cannabinoids may have important differences in action. Since major discoveries in the past 20 years, we now know that cannabis acts in most cases through the interaction at specific neurotransmitter sites now called Cannabinoid Receptors. Two types of cannabinoid receptors have been described, the CB1 receptor, located primarily in the central nervous system and the CB2 receptor, located in the periphery (spleen and immune system). When a cannabinoid interacts with the CR receptor, the response is a secondary change in calcium channels located in the neuron cell membrane. The change in calcium current will be reflected in the response of the neuron. Therefore, the ingested cannabinoid acts by causing the release of other intracellular substances to cause a response.
The response to cannabinoids is further complicated by the fact that the pharmacological and behavioral effects are mediated by interactions at opiate, acetylcholine, dopamine and GABAergic systems in the CNS. For example, interactions at opiate receptor sites are important in treating pain, acetylcholine in memory, dopamine in movement disorders such as Parkinson disease, and GABA in spasticity and seizure disorders. Pharmaceutical research is directed to the development of individual cannabinoid drugs to treat stroke, MS, Parkinson disease, pain, and epilepsy.
In summary, cannabis acts at specific nerve cell membranes which results in a change of electrical potential with resultant neuronal activity. The interactions are complex and involve a number of brain receptor sites. Cannabinoid neuroscience research is one of the most exciting areas of research with the potential for significant medical benefit in the near future.
Denis J. Petro, MD
Posted: February 23, 2004 by webmaster.
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Q: Is there a difference between smoking marijuana or eating it? I mean physiologically in the body is it processed differently so therefore would affect us differently or is it just a patient preference thing? -- Rhonda
A: The question regarding the difference between inhaled and orally ingested cannabis is a good one.
Cannabis is metabolized by the liver into a number of substances which are then excreted via the biliary system. If one inhales marijuana smoke in the lungs, the chemicals in the smoke (cannabinoids) do not pass thru the liver and are distributed to the brain directly. In theory then if one is to maximize the distribution of cannabinoids to the brain, inhaled marijuana is both faster in action and more efficient in delivery of the drug. A second method to avoid the liver in drug absorption is to use a "lingual" formulation. In this method, the drug is taken by mouth but is absorbed in the lining of the mouth. This is the method some cardiac drugs such as nitroglycerin are administered. So if rapid absorption and distribution is needed, the best method is via inhalation.
In most MS patients, oral use is adequate to treat symptoms such as muscle spasms, pain and bladder complaints. Also, oral use avoids the potential for chronic lung irritation associated with smoking. I've seen a number of cookbooks which describe methods to add cannabis to foods such as in cookies or brownies. I do not have any of the recipes in my possession, I have written a medical article "Cannabis in Multiple Sclerosis: Women's Health Concerns" which may be of interest to you. If you provide a mailing address, the publication will be sent to you.
Denis J. Petro, MD
Posted: January 21, 2004 by webmaster.
Created on 07/28/2005 10:52 AM by mspuadmin
Updated on 07/28/2005 10:56 AM by mspuadmin
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