Last month, Philadelphia health officials discovered that the city's latest surge of drug overdoses was linked to heroin contaminated with a synthetic cannabinoid commonly known as K2 — the same deadly mix that created a similar surge in July. The latest outbreak sickened at least 110 people and killed seven around the city. July's toll: At least 165 overdoses and 10 deaths in a single weekend.

And in August, prisons across Pennsylvania were put on lockdown over fears that corrections officers were being poisoned by synthetic marijuana, sparking stringent new rules for inmate mail.

Philadelphia emergency-room doctors said it was clear that many overdose victims displayed symptoms not typical of an opioid overdose: hallucinations, repeated vomiting, and severe agitation that, for some, required so much sedation that they had to be put on ventilators to breathe.

Used on their own, synthetic cannabinoids are 30 times more likely to harm you than regular marijuana. Even with these risks, 7 percent of high school seniors and about 17 percent of adults have tried synthetic cannabinoids. It is easy to understand why synthetic substitutes are alluring. They are easy to purchase, relatively inexpensive, produce a more potent high, and don't emit the typical marijuana scent. And, they are much harder to detect in the urine or blood than marijuana.

As an intensive-care pharmacist and clinical pharmacologist, I have been researching street drugs for more than a decade to help emergency room, critical care, and poison control clinicians treat overdosing patients.

Why is using synthetic marijuana risky?

When you open a packet of a synthetic cannabinoid, such as K2 or Spice, and pour the dried vegetation into your hand, it looks like marijuana. These dried leaves and stems can be inert or come from psychoactive plants, such as wild dagga. Some of these plants are contaminated with heavy metals, pesticides, mold, or salmonella.

However, synthetic cannabinoids are anything but natural. They are mass-produced overseas and then shipped in bulk to the United States, where they are dissolved and then mixed with dried vegetation, which absorbs the liquid. This process is very imprecise, so the dose in one packet can differ greatly within or between batches.

There are several hundred synthetic cannabinoids in existence, and they all stimulate cannabinoid type 1 receptors (CB1), just like the active component in natural marijuana, THC, that provides the high. But they do so with different intensities and for differing periods of time. Some incorporate the central ring structure of the THC molecule before laboratory modification, but many others do not. More problems arise because some synthetic cannabinoids stimulate non-cannabinoid receptors and cause unanticipated effects. There is no way to know which synthetic cannabinoids are actually in the product you purchased.

Natural marijuana does not comprise only THC. The other constituents in natural marijuana, such as cannabidiol, help temper the negative impact of THC but are absent in synthetic cannabinoids. Also, there is a risk that synthetic cannabinoids can be adulterated with other chemicals, ranging from opioids to rat poison.

Synthetic cannabinoids were initially designed by legitimate researchers in the U.S. and around the world who were looking to explore the function and structure of cannabinoid receptors. They did not intend for illegal drug labs to use their recipe for mass production.

What are the consequences of using these drugs?

In addition to giving the user a high, the primary psychological and neurological effects of synthetic cannabinoid use include anxiety, agitation, and paranoia; psychosis and seizures have also occurred. The anxiety and psychosis can cause the heart to beat fast and even trigger heart attacks or strokes when the body's adrenaline gets flowing. Many people suffer upset stomach with synthetic cannabinoids, and vomiting is common (which is paradoxical, because medical marijuana is used to prevent vomiting). Finally, there is a risk of muscle and kidney damage.

Rarely, people reported having trouble breathing, but in some cases this is due to adrenaline release. In other cases, the butane that was used to extract THC from marijuana before laboratory alteration was not removed. The butane ignites during smoking and damages the lungs. Early detection and aggressive treatment can help prevent severe adverse events or death.

What can we do to protect ourselves?

Many of the risks of synthetic cannabinoids and other illegal drugs of abuse arise because of contamination, adulteration, substitution, and inconsistent dosages. As long as people are able to manufacture, transport, and sell these drugs secretly, there is no way to assure buyers of a consistent quality product. Public health personnel, teachers, and parents need to educate adults and students alike about the inherent risks of the drugs in their pure form but should also include the risks associated with poor manufacturing practices.

People generally prefer natural marijuana to synthetic forms, but as long as natural marijuana remains illegal, highly desired, easily detected, and periodically unavailable, the desire to purchase synthetic forms will persist.

Finally, synthetic cannabinoids are primarily manufactured overseas. Foreign governments, especially in Asia, need to crack down on illegal drug factories and better scan freight for illegal drugs. In addition, shipping companies need to do more to detect the illegal transport of drugs into the United States. There are hand-held detectors that can help identify some but not most synthetic cannabinoids. However, detection will still be painstakingly slow.

C. Michael White is a professor and head of the department of pharmacy practice at the University of Connecticut. This article is republished from The Conversation under a Creative Commons license.