IN A RECENT poll conducted by Medscape, a website directed at health care providers, 76 percent of physicians and 89 percent of nurses said they thought marijuana should be available as a medicine. That's a big change from the attitude in the medical community a decade ago, when few health providers believed (or would acknowledge) that cannabis had any medical utility. That was not surprising; physicians receive most of their new drug education from journal articles or from drug company advertisements and promotions, and neither of these sources provides information about medical marijuana.

The dramatic change of view is the result of clinical experience. Doctors and nurses have seen that for many patients cannabis is more useful, less toxic, and less expensive than the conventional medicines prescribed for diverse syndromes and symptoms, including multiple sclerosis, Crohn's disease, migraine headaches, severe nausea and vomiting, convulsive disorders, the AIDS wasting syndrome, chronic pain, and many others.

A mountain of anecdotal evidence speaks to marijuana's medical versatility and striking lack of toxicity. Even the federally sponsored Institute of Medicine has grudgingly acknowledged that marijuana has medical uses.

However, the government itself refuses to learn. Its official position, as stated recently by the new DEA administrator, is that "marijuana is not a medicine."

When it is at last obliged to acknowledge the medical value of marijuana, the government will be faced with the problem its present attitude has allowed it to avoid. How can it grant access to marijuana for medical purposes while prohibiting its use for other, disapproved purposes? One solution is what I would call "pharmaceuticalization": the development of prescription medicines derived from the therapeutically active components of cannabis and synthetic variants of these molecules.

This process has already begun in a small way. The Food and Drug Administration, under pressure from a growing number of physicians and patients, approved Marinol for the treatment of the nausea and vomiting of cancer chemotherapy. Marinol is synthetic tetrahydrocannabinol, the primary active cannabinoid in marijuana, packed in a capsule with sesame oil so that it cannot be smoked.

But relatively few patients have found Marinol useful. It is less effective than marijuana for several reasons. Because it must be taken orally, the effect appears only after an hour or more. That eliminates one of the main advantages of smoked or vaporized inhaled cannabis, which works so quickly that the patient can adjust the dose with remarkable precision. Furthermore, Marinol is more expensive than marijuana, even with the prohibition tariff that raises the price of illicit cannabis.

Several other products, including extracts of marijuana, are in the pipeline, but they are unlikely to be any more useful or less expensive than plant marijuana. Even if pharmaceutical companies invest the many millions of dollars it will take to develop useful cannabinoid products, they will not displace natural marijuana for most purposes. And because the primary, and for many the only, advantage of these drugs will be legality, their manufacturers will have an interest in vigorously enforced prohibition that raises the price of the competitive product, street marijuana.

The realities of human need are incompatible with the demand for a legally enforceable distinction between medicine and all other uses of cannabis. Marijuana not only has many potential medical uses, but can also safely enhance many pleasures and ease many discomforts of everyday life. In many cases what lay people do in prescribing marijuana for themselves is not very different from what physicians do when they provide prescriptions for psychoactive or other drugs.

The only workable way of realizing the full potential of this remarkable substance, including its full medical potential, is to free it from a dual set of regulations -- the laws that control prescription drugs, and the often cruel and self-defeating criminal laws that control psychoactive substances used to for nonmedical purposes. These mutually reinforcing laws strangle marijuana's uniquely multifaceted potential. The only way to liberate the potential is to give marijuana the same legal status as alcohol, a far more dangerous substance.

Marijuana should be removed from the medical and criminal control systems. It should be legalized for adults for all uses.

Dr. Lester Grinspoon, an emeritus professor of psychiatry at Harvard Medical School, is author of "Marihuana Reconsidered" coauthor of "Marijuana, the Forbidden Medicine."

© Copyright 2003 Globe Newspaper Company

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