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Medicinal Cannabis in the Treatment of Chronic Pain Syndromes
Yesterday, we discussed the collected randomized-controlled trial evidence base that supports the use of inhaled smoked cannabis to treat neuropathic pain. Today, we will discuss vaporization as a smokeless delivery system for cannabis administration. We will also review the results of some clinical studies examining marijuana vaporization for the treatment of neuropathic pain.
Editors' Note: Medical marijuana has become an important area of study in healthcare. Doctors and healthcare professionals must understand the medical, legal, social and political issues to best respond to their patients’ questions and attend to their needs. This content area is not intended to encourage or dissuade the use of medical marijuana, but has been created to provide a balanced portrayal of the research in this area. The Drug Enforcement Agency issued “The DEA Position on Marijuana” in January 2011, which is their most recent position statement and provides information about medical marijuana and issues related to the conflicts between federal and state law.
Vaporization is a smokeless delivery system used for cannabis inhalation. Vaporization uses warm air or heat of 180°C to 200°C, rather than a flame, to convert cannabinoids and other compounds found in herbal cannabis into a fine mist that can be inhaled. Since temperatures are far lower, no combustion by-products such as soot or polycyclic aromatic hydrocarbons are produced. Due to their volatility, cannabinoids will vaporize at temperatures of 180°C to 200°C, but will not combust at these temperatures (32).
Vaporizers fall into two general categories: conduction-based and convection-based. Conduction-based vaporizers heat herbal cannabis on a surface that is warmed, such as a metal plate, which then allows compounds to passively volatilize. Meanwhile, the consumer generates a steady inhalation, similar to the technique used by asthma patients with metered-dose inhalers or nebulizers to achieve pulmonary administration. Convection-based vaporizers allow a stream of warm air to pass through the herbal material. Then, the air carries the volatilized vapor into a separate airtight reservoir attached to a spring-activated one-way valve that allows a consumer to inhale aliquots of the vapor. In an August 2005 perspective piece on medical marijuana by Susan Okie, M.D., the New England Journal of Medicine published a photograph of a convection-based vaporizer with the following caption: “Vaporizer System for the Administration of Marijuana. The cannabis is placed in the chamber and heated to a temperature below that required for combustion. The balloon fills with vapor that contains the active ingredients without the tar or particulates thought to be responsible for most of the drug’s adverse effects on the respiratory tract. The patient inhales the vapor from the balloon.” (33).