Priapism is defined as an erection that lasts for longer than four hours. Erections are usually painful and unrelated to sexual stimulation or arousal. Although a relatively uncommon condition, priapism tends to present more commonly in particular individuals, such as those who suffer from sickle cell anemia. Approximately 42 percent of adults with sickle cell anemia will experience an episode of priapism.

Clinicians have identified various risk factors that may predispose a person to develop priapism. Blood disorders, such as sickle cell anemia, are commonly implicated. Certain medications, such as those used to treat depression and erectile dysfunction, have also been linked to priapism. Traumatic injury and the use of alcohol, cocaine, and marijuana are also risk factors that seem to increase the likelihood of developing priapism.

A recent report published in the Journal of Cannabis Research discussed the case of a 32-year-old African American man who presented to the emergency department with a persistent erection that had lasted for more than six hours.

The patient had previously suffered similar episodes of a prolonged erection (“Priapism”), starting at age 16. The initial onset coincided with the first time he used cannabis. Episodes of painful, prolonged erection repeatedly occurred throughout his teenage years, particularly when he was using cannabis heavily around the ages of 16 and 17. It appeared to cease when the patient was in his 20s, which was a time during which he abstained from cannabis use.

The authors investigated whether any previous research had described a patient with priapism within the context of cannabis use. However, they were unable to find any case-studies that discussed cannabis use in patients experiencing priapism in the absence of pre-existing risk factors, such as disease and drug use.

After interviewing to elicit the patient’s medical history, alongside physical and laboratory assessments, clinicians determined that the patient did not have any known predisposing-factors for the development of priapism except for cannabis use. He tested positive on a urine drug screen but did not show any indication of the use of other substances. Therefore, this is the first study of its kind to have documented cannabis-associated priapism in a context when all other risk factors have been ruled out.

Theories and Explanations

The authors of this study considered several potential mechanisms that could explain why cannabis might trigger an episode of priapism. Delta-9-tetrahydrocannabinol (THC), the primary psychoactive constituent of cannabis, exerts its litany of effects through stimulating cannabinoid receptors throughout the body. There are two types of cannabinoid receptors: Cannabinoid Receptor 1 (CB1) and Cannabinoid Receptor 2 (CB2).

THC primarily acts upon CB1, which can be found (among many other areas) within the testicular tissue and its blood vessels. CB1 receptors, when stimulated, promote nerve-signaling throughout the body, which initiates and maintains a penile erection. Theoretically, excessive cannabinoid stimulation of the nervous system could lead to the type of erection seen in priapism. Additionally, direct stimulation of the blood supply to the penis could have a similar effect.

Cannabis use, particularly that of a chronic nature, has also been shown to affect the blood itself, rather than just the vessels that contain it. THC can cause the blood to clump and clot. However, it is important to mention, THC also shows anti-coagulant activity. Clotting of the blood within the vessels supplying the penis could lead to a very painful and prolonged erection, like that seen in priapism. This mechanism of clotting within the penile vessels is not entirely dissimilar to that seen in sickle cell disease, a disorder where red blood cells have reduced ability to deform and increased strength of clotting.

Significance and Limitations

In looking at the medical history of the patient featured in this case study, it is clear that he had multiple initial episodes of priapism coinciding with when he first started using cannabis: from the ages of 16-17. At 18 years of age, the patient stopped using cannabis, subsequently reporting no further episodes of priapism throughout his 20s, in which he remained abstinent. The patient then resumed cannabis consumption six months before his emergency room admission.

Throughout the six-month period during which the patient was using cannabis, he reported that he had experienced at least a dozen episodes of erections that were similar to that seen in priapism. However, these resolved naturally and lasted for less than four hours.

In light of the lack of other predisposing risk factors, the authors concluded that cannabis use was a likely cause for priapism in the patient. The recognition of this association might provide insights for treatment and prevention within future clinical practice. If future case reports report similar findings, clinicians may be able to mitigate priapism in those who use cannabis through the use of proper counseling and patient education. This is particularly important in those with a pre-existing disorder, such as sickle cell anemia, which can predispose a person to priapism. The knowledge of cannabis increases the risk of priapism in those already vulnerable may help many patients in the future.

It is important to note that a single case study does not provide conclusive results that can be applied to a broad scope of patients. As stated by the authors, this is the first case study of its kind. Although this study provides a unique insight into the association between priapism and cannabis, we cannot yet determine whether this link is correlative or causative.

Final Thoughts

This study provides a unique account of a patient case that sheds light on the association between cannabis use and the development of priapism. There appears to be a strong association between cannabis use and the onset of priapism in this particular patient. These findings can be used to increase awareness for clinicians who may find patients presenting similarly.

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