A dried flower bud of a Cannabis plant.Image credit: Evan-Amos, Wikimedia CommonsCORVALLIS, Ore. – The emergence of the legal recreational use of marijuana, in Oregon and elsewhere, has raised a wide range of questions about this drug – especially after decades of prolonged debates, some groups calling it harmless and others a “gateway” drug that should still be illegal.

At Oregon State University, pharmacological experts are helping to answer these questions. They are speaking to many public and professional groups around the state, as well as OSU pharmacy students, and trying to raise the level of medical knowledge about marijuana, based on the best available science.

That’s a challenge in itself, they say, because despite vehement arguments on both sides of these issues over many years, comparatively little valid scientific research has been done on marijuana. Some key questions remain unanswered, even though there’s evidence the drug has been used by humans for more than 4,000 years, and its use in the U.S. is now expanding significantly as legal restrictions weaken.

That being said, there’s a lot that is known.

First and foremost, today’s commercially available marijuana is not the same product that some may remember from the 1960s or 70s. It is far more potent.

“Marijuana today has a much higher content of THC, its psychoactive component, than it did in the past,” said Jane Ishmael, an associate professor of pharmacology in the OSU College of Pharmacy and a member of the Oregon Public Health Division’s Retail Marijuana Scientific Advisory Committee. Ishmael is an expert on drug action who teaches pharmacy students about drugs of abuse, ranging from alcohol to nicotine or even some over-the-counter and prescription products.

“The average THC content in marijuana decades ago used to be about 4 percent, but with years of improved cultivation techniques and plant improvements it’s now around 17 percent,” she said. “It’s even higher in some specific strains, meaning that today’s marijuana products can be at least four times stronger. For any older people who are considering use of marijuana again now that’s it’s legal, that’s something they should be aware of.”

An important research finding that’s more recent, Ishmael said, is how this age-old drug actually works.

Studies reported in the 1990s showed that the human body contains many receptor targets for THC and also produces “endocannabinoids.” Normally, the endocannabinoid system plays a role in regulation of appetite, pain control, pleasure and other sensations.

It was discovered that chemicals in marijuana, such as THC, bind to cannabinoid receptors in the brain and modulate the release of other neurotransmitters. These actions explain many of the biological impacts of marijuana for sensations of pleasure, its medicinal potential, and other aspects of neurobiology.

“One thing that people must understand is that marijuana is a recreational drug,” Ishmael said. “We’ve now chosen to make it legal, but like other drugs such as alcohol, that’s not synonymous with saying it’s completely safe and harmless. If people choose to use it, they should understand how it works, what it does, and when or with whom it should not be used.”

Among key points to consider, the experts said:

• Marijuana use is inappropriate for women who are, or may become pregnant or are nursing. THC can pass directly to the baby during pregnancy and breastfeeding, and may affect the baby. There is no known safe amount of marijuana use during pregnancy.
• For similar reasons, the laws restricting retail marijuana use to those over 21 years of age are important.
• Marijuana, as many users will attest, causes feelings of relaxation, pleasure, or a stimulated appetite.
• Marijuana can cause immediate difficulties in thinking and concentrating, dry mouth, blurred vision, increased heart rate and blood pressure, and feelings of anxiety or panic.  
• Marijuana can impair coordination, slow reaction times, change perceptions of time, danger, and lowers the perception of risk. These issues, along with changes in the ability to think and concentrate, are the clear reasons why it should never be used when driving, riding a bike or operating dangerous equipment.
• For similar reasons, a person should not ride in a vehicle, or let others ride, if it’s known the driver is under the influence of marijuana. 
• The effects of marijuana, and the time it takes to clear the body, vary with the individual and mode of use. It has an effect much more quickly if inhaled or vaporized, and most impacts usually wear off after three to four hours when used this way.
• If marijuana is eaten, as it is sometimes combined with foods to produce what are known as edibles, the effects will typically take longer to start and can last longer, up to 10 hours after eating.
• Any use of marijuana in a food or candy is a common-sense parental concern in a household where children may be present. Marijuana can make children sick and should always be kept out of sight and reach of children.
• Although THC is not believed to be a carcinogen, marijuana smoke contains the same cancer-causing chemicals as tobacco smoke, yet the health risks from second-hand exposure to marijuana smoke have been much less studied. Heavy smokers of marijuana can experience chronic bronchitis, including a chronic cough, sputum production and wheezing.
• Considerable caution should be taken when marijuana is used in conjunction with other prescription medications that act on the central nervous system, such as drugs that have a sedative effect, or with medicines that are prescribed to treat mental illness.
• Even though the psychoactive effects of marijuana may wear off in a few hours, metabolites from its use can still be detected in the blood or urine for up to three weeks – an issue as it relates to employers that forbid its use, or the complex legal issues of driving under the influence of marijuana.

Some reliable information is now emerging about the medicinal use of marijuana to improve symptoms in a variety of chronic conditions, the researchers said.

There is evidence that marijuana can aid with some types of pain control, such as painful muscle spasms associated with multiple sclerosis and neuropathic pain. It can also help relieve nausea and vomiting associated with chemotherapy, although other drugs are now available with similar effectiveness for that purpose. And it has been shown to improve quality of life in patients struggling with loss of appetite and maintaining body weight, including AIDS patients.

“Frankly, there’s still a lot we don’t know,” Ishmael said. “Marijuana contains more than 400 chemicals and we’ve focused most research just on one of them. Hopefully some future research will help better inform us about the complete range of effects, whether positive or negative.”

Roberto Linares, a senior instructor in the OSU College of Pharmacy who is also on the Oregon Board of Pharmacy, said that the legalization of marijuana will pose many challenges for medical experts in the near future.

“Pharmacies have not yet shown interest in distributing it, in part because that could conflict with the federal laws that apply to their operation,” Linares said. “But people will be coming to their doctors, to their pharmacists and other health professionals, with a lot of reasonable questions if they choose to use legalized marijuana. That’s one reason we’re trying to put out as much valid information as we can.”

Another issue almost completely unexplored, the researchers said, is the interaction of marijuana with many other legal medications. Entire books and computer programs exist with most drugs to help pharmacists analyze precisely how they might interact with another drug. With marijuana, that’s mostly a blank page.

“One other thought that people should consider is that everyone is an individual,” Ishmael said. “People’s reactions to drugs vary widely, it’s not easily predictable. With some, the effects of marijuana use will be much more intense than with others. That should be kept in mind by anyone who is considering its use.”