Synthetic marijuana, known as SPICE or K2, does not show up in drug screens but can negatively impact kidney function.

University of Alabama at Birmingham (UAB) nephrologists have reported for the first time in medical literature cases of acute kidney injury directly linked with synthetic marijuana use. The case studies are reported online in the Clinical Journal of the American Society of Nephrology and will appear in the March 2013 print edition of the journal.

The authors report that nephrotoxicity — the poisonous effect of a substance on the kidneys — from designer drugs such as SPICE or K2, which mimic the effects of marijuana but are man-made and cannot be detected in routine drug tests, should be considered when a patient presents with acute kidney injury and no other evident cause. This is especially true for young adults with negative urine drug screens, said the paper’s senior author Denyse Thornley-Brown, M.D., associate professor in the UAB Division of Nephrology.

Thornley-Brown said the use of relatively cheap synthetic marijuana preparations has increased significantly over the past few years, mostly among young adults who have a desire to experiment with a substance that is difficult to detect. The relatively low cost, about $20 per gram, is another reason for its popularity.

In the journal, Thornley-Brown and colleagues outlined four different cases of previously healthy young men whose acute kidney injury was linked to ingestion of synthetic marijuana. All the patients were residents of the same northeastern Alabama community and presented to UAB or a community hospital within a nine-week period showing symptoms of nausea, vomiting and abdominal pain after using synthetic marijuana.

“Cases of acute coronary syndrome associated with synthetic marijuana use have been reported, but our publication is the first to associate use with acute kidney injury,” said study co-author Gaurav Jain, M.D., assistant professor in the Division of Nephrology. “Tachycardia and seizures have also been reported with synthetic cannabinoids.”

In the journal, Thornley-Brown and colleagues outlined four different cases of previously healthy young men whose acute kidney injury was linked to ingestion of synthetic marijuana.

Three of the patients had acute kidney injury marked by the excretion of an abnormally small volume of urine, known as oliguric acute kidney injury, and the fourth had a decrease in effective blood flow to the kidney, known as prerenal acute kidney injury. Three of the patients underwent a kidney biopsy that showed acute tubular necrosis, which is the death of cells that form the minute canals in the kidney that secrete, reabsorb, collect and transport urine. Left untreated, this can cause the kidneys to shut down. In these four cases, the patients recovered kidney function, and none required dialysis.

Thornley-Brown said the patients’ common history of synthetic marijuana ingestion suggests a possible pathogenic role of its preparation in these patients’ acute kidney injury. The time of occurrence and geographic clustering of the cases is consistent with a common toxic exposure. However, due to the small number of patients, the inability to obtain a sample of the synthetic marijuana involved and the patients’ serum and urine samples being discarded by the time of the investigation, the researchers found it difficult to argue for a causative role of the preparations in acute kidney injury.

But, Jain added, given that synthetic marijuana preparations involve using several additives, the causative agent of the acute kidney injury in these cases may have been an additive rather than the cannabinoid itself.

“There is very little information regarding the ingredients in synthetic cannabinoids that are sold on the streets, although it is known that additional compounds are added to the preparations,” Jain added. “It is very likely that a possible nephrotoxin adulterated the preparation used by our patients.”

The authors recommend that physicians inquire about the use of designer drugs when evaluating patients with acute kidney injury — especially in cases where the etiology is unknown and the urine drug screen is negative. For young people, the take-home message should be that these drugs may have unanticipated and potentially life threatening side effects, and they should be avoided.

“If they don’t get to a physician in time, the damage to their kidneys could be permanent, and they could end up on dialysis,” Jain added.

Gautam Kantilal Bhanushali, Huma Fatima and Leah J. Leisch, all from UAB, were co-authors on the study.