Several dozen medical marijuana patients and caregivers gathered on a recent week night for a two-hour seminar at Forgotten Knowledge Collective in Valley Springs. After giving them an overview of the biology and science behind medical pot, biochemist Samantha Miller turned to one of the biggest questions facing the medical marijuana movement: to smoke or not to smoke.

Miller urges medical marijuana patients to cast off their butane lighters.

“When you are smoking Lady, you are losing some of your active ingredient to combustion,” Miller said.

And then there’s the lung irritation that comes from inhaling butane and the jagged soot from burning plant matter at about 1,200 degrees.

Alternatives to smoking include edible forms of the drug, skin patches and tinctures that use alcohol or glycerine solutions to deliver the active compounds. One of the most popular, however, is the use of devices that vaporize the active ingredients in marijuana without burning it.

“Smoking it is not good for you, OK?” said Dr. Stacey Kerr, a Santa Rosa physician and a member of the Society of Cannabis Clinicians.

She advises patients to seek other methods. “The least they need to do is to use a vaporizer if they are going to inhale.”

Vaporizers are not cheap. The devices can cost $200 or more and can be tricky for first-time users to operate. Also, medical marijuana users accustomed to smoking often initially report that vaporizing does not seem to yield the same benefits.

Miller acknowledged that. “The effects you are going to feel, the high, is going to be different than when you smoke,” she said.

The active compounds in marijuana vaporize at relatively low temperatures.

A study by Dr. Donald Abrams at the University of California, San Francisco, concluded that vaporizing is a “safe mode of delivery” and that participants in the study came to prefer it.

One advantage to both smoking and vaporizing is that patients can gradually consume the medication, which enters the bloodstream almost instantly, until reaching the appropriate dose.

Eaten marijuana, in contrast, is difficult to dose accurately, experts say. Not only does the eaten form take effect more slowly, but the breakdown of marijuana compounds in the liver can actually transform THC into a more potent psychoactive material.

“That is many times more psychoactive than the original form,” said Kerr. “This has made people afraid to eat it. You eat it once, (and get) too much, and you never want to eat it again.”

Another option available so far in the United Kingdom and Canada, but not the United States, is a preparation called Sativex, manufactured by GW Pharmaceuticals. Sativex is an extract from marijuana plants that contains precise amounts of THC and CBD, as well as small amounts of many other compounds in the plant.

Sativex comes as an oral spray. If a patient pumps the spray once he or she will get exactly 2.7 milligrams of THC and 2.5 milligrams of CBD. This level of dose precision is so far almost impossible to achieve with smoked, vaporized or eaten marijuana.

Doctors in Britain and Canada typically prescribe Sativex for pain and to relieve spasticity associated with multiple sclerosis. Clinical trials are now underway that could lead to its approval in the United States.