act on cannabinoid receptors and that this “cannabinoid system” appears to influence movement, memory, immunity, and pain sensation (see Chapter 2). The more research reveals about the diverse effects of various cannabinoids, the greater the likelihood that scientists will develop cannabinoid drugs that effectively treat specific symptoms, with a minimum of adverse side effects.

The second recommendation encourages the development and clinical testing of cannabinoid medicines for a few promising indications: pain relief, control of nausea and vomiting, and appetite stimulation. It also emphasizes the need to develop safer and more effective methods for administering these drugs to patients. While smoking marijuana allows cannabinoids to take effect rapidly and permits patients to titrate their dose—that is, to inhale just enough to achieve relief from their symptoms—it also has numerous drawbacks, particularly for people with health problems (see Chapter 3). Oral THC (in the form of dronabinol, sold as Marinol) has received approval from the FDA for treatment of nausea and vomiting as well as appetite loss. But Marinol takes effect slowly and cannot be effectively titrated by the user. Vomiting, in particular, would be far more amenable to treatment by inhalation than with a pill that needs to stay down.

The IOM team also urged, in its third recommendation, that clinical trials be designed to gauge the psychological effects of cannabinoid drugs. Marijuana's active ingredients, especially THC, produce feelings of well-being, calm, and sedation in many people. These effects could augment other therapeutic benefits of cannabinoids for some patients, but others may mistake good feelings for relief from their symptoms. The more researchers learn about how cannabinoids' physical and psychological effects interact, the better they can put the compounds to medical use.

Marijuana smoking clearly harms the cells of the respiratory system, in much the same way tobacco smoke does. But since no definitive study has shown that smoking marijuana causes cancer or chronic obstructive pulmonary disease, the IOM team called for such research in its fourth recommendation. Many studies suggest that marijuana smoke plays a role in causing respiratory disease, but no firm evidence exists to either support or refute this conclusion. This question is particularly important to AIDS patients who smoke marijuana to soothe several symptoms

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