An important aspect of any medical treatment is making sure it’s safe and effective.

Author and pharmacologist Dr. Nichol Iverson explained the dosing testing that has been conducted to date:

“Laboratory animals (rats, mice, dogs and monkeys) can tolerate doses of up to 1000 mg/kg. This would be equivalent to a 70 kg person swallowing 70g of the drug—about 5,000 times more than is required to produce a high. Despite widespread illicit use of cannabis, there are very few, if any, instances of people dying from an overdose.”

In 1988, the Drug Enforcement Administration’s Law Judge, Francis Young—responding to a petition to reschedule cannabis under the Controlled Substances Act (to make it easier to conduct research into its efficacy)—said, “In strict medical terms, marijuana is far safer than many foods we commonly consume…. Marijuana, in its natural form, is one of the safest therapeutically active substances known to man. By any measure of rational analysis, marijuana can be safely used within the supervised routine of medical care.”

The Institute of Medicine (IOM), more than 10 years later, when investigating the physiological risks of cannabis use, concluded that “Marijuana is not a completely benign substance. It is a powerful drug with a variety of effects. However, except for the harms associated with smoking, the adverse effects of marijuana use are within the range of effects tolerated for other medications.”

Research conducted on the long-term effects of cannabis use since the IOM report has revealed that consumption of moderate amounts of cannabis to be remarkably safe, particularly when compared to other therapeutically active substances — most significantly is the relative lack of overdose risk. According to a 1995 review prepared for the World Health Organization, “there are no recorded cases of overdose fatalities attributed to cannabis”. Furthermore, a review of clinical investigations and observational studies detailed that investigators “did not find a higher incidence rate of serious adverse events associated with medical cannabinoid use.”

Toxicity and overdose risk

It is estimated that to overdose, an average sized human would need to consume 1,500 pounds of cannabis in 15 minutes—an act that is truly not possible. Using a system called LD50, which indicates the lethal dose of a drug or substance for 50 percent of the population, researchers have determined that cannabis is one of the safest substances known and one from which it is theoretically impossible to overdose. Dr. Lester Grinspoon, a psychiatry professor at Harvard Medical School, wrote the following in 1995 in the Journal of the American Medical Association:

“One of marihuana’s greatest advantages as a medicine is its remarkable safety. It has little effect on major physiological functions. There is no known case of a lethal overdose; on the basis of animal models, the ratio of lethal to effective dose is estimated as 40,000 to 1. By comparison, the ratio is between 3 and 50 to 1 for secobarbital and between 4 and 10 to 1 for ethanol [alcohol].”

“Marihuana is also far less addictive and far less subject to abuse than many drugs now used as muscle relaxants, hypnotics, and analgesics. The chief legitimate concern is the effect of smoking on the lungs. Cannabis smoke carries even more tars and other particulate matter than tobacco smoke. But the amount smoked is much less, especially in medical use, and once marihuana is an openly recognized medicine, solutions may be found; ultimately, a technology for the inhalation of cannabinoid vapors could be developed.”

The technology to which Dr. Grinspoon alluded is now available via desktop and pocket vaporizers from dozens of manufacturers. Because research regarding the rate of lung cancer and pulmonary diseases, even among chronic cannabis consumers, has shown that marijuana smokers experience no greater risk of lung cancer or related diseases. In fact, research has demonstrated that heavy cannabis smokers are at no greater risk of lung cancer than non-smokers.

Despite these findings, cannabis can’t be considered “harmless.” It delivers a variety of physiological effects, including dilation of blood vessels and rapid heart rate. In very limited cases, especially among those with cardiac conditions, these symptoms can be dangerous. However, these adverse effects are well within the range of other FDA-approved medications. Also, because of tolerance building, users often overcome such reactions to the herb.

Dr. Grinspoon added:

“The greatest danger in medical use of marihuana is its illegality, which imposes much anxiety and expense on suffering people, forces them to bargain with illicit drug dealers, and exposes them to the threat of criminal prosecution.”