Cannabis and Prolonged Erections (Priapism)
Cannabis use can cause priapism (prolonged, painful erections) in rare cases, as documented in multiple case reports, though this is not listed as a common side effect in clinical guidelines. 1, 2, 3
Evidence on Cannabis and Priapism
Case Reports
Several case reports have documented the association between cannabis use and priapism:
- A 37-year-old man developed priapism after cannabis use, requiring emergency aspiration of blood from the corpora cavernosa and intra-cavernous injection of ephedrine 1
- A 28-year-old man experienced a 58-hour priapism after regular use of synthetic cannabinoids, which did not resolve with standard treatments and ultimately required penile prosthesis implantation 2
- A 32-year-old man with no other risk factors developed recurrent (stuttering) priapism attributed to cannabis use alone 3
- Another case involved a 24-year-old man with multiple episodes of priapism who admitted to using marijuana and cocaine, along with anabolic steroids 4
Mechanism
The exact mechanism by which cannabis might cause priapism is not fully understood, but may involve:
- Cannabis affects vascular tone through cannabinoid receptors
- THC acts as a partial agonist at cannabinoid receptor Type 1 (CB1) and Type 2 (CB2) receptors, causing cardiovascular effects 5
- These effects are primarily mediated through beta-adrenergic stimulation and alterations in vascular tone 5
Cardiovascular Effects of Cannabis
Cannabis use has documented effects on the cardiovascular system that may contribute to this rare phenomenon:
- THC can cause orthostatic hypotension and is associated with myocardial ischemia in at-risk individuals 5
- Cannabis use is linked to increased heart rate (tachycardia), changes in blood pressure, and alterations in peripheral vascular resistance 5
- THC can affect cerebral blood flow and vasodilation 5
Clinical Considerations
Risk Factors
The risk of cannabis-induced priapism may be increased by:
- Higher THC concentrations (modern cannabis has significantly higher potency, with THC levels increasing from 9% in 2008 to 17% in 2017, and concentrates reaching up to 70%) 6, 5
- Method of consumption (smoking, vaping, edibles) may affect risk profiles 6
- Individual susceptibility factors that remain poorly understood
Management
If a patient presents with priapism and reports cannabis use:
- Treat priapism as a urological emergency according to standard protocols
- Recognize that cannabis may be the causative agent
- Consider aspiration of blood from the corpora cavernosa and intra-cavernous injection of vasoconstrictors as first-line treatment 1
- Be aware that cannabis-induced priapism may be resistant to standard treatments in some cases 2
Limitations of Evidence
- Most clinical guidelines on cannabis, including the ASCO guideline 6 and ACP position paper 6, do not specifically mention priapism as a known side effect
- The evidence consists primarily of case reports rather than large-scale studies
- Confounding factors (such as concurrent use of other substances) may be present in some cases 4
- Research on cannabis and male sexual function has been limited and sometimes contradictory 7
Recommendations for Patients
Patients using cannabis should be informed that:
- Priapism is a rare but documented potential side effect of cannabis use
- Priapism is a medical emergency requiring immediate treatment to prevent permanent erectile dysfunction
- They should seek immediate medical attention for any erection lasting longer than 4 hours
The increasing potency of modern cannabis products may increase the risk of adverse effects, including rare cardiovascular complications like priapism 6, 5.