Safety Profile

There are both peripheral and central nervous system effects related to opioid and cannabis use. Peripherally and centrally, opioids cause reduced peristalsis leading to constipation and pruritis.11 However, it is the CNS action that increases somnolence, obtundation, miosis, and respiratory depression. The latter side effect is generally regarded as the source of opioid related deaths. Centrally, effects are also associated with decreasing levels of systemic tolerance, hyperalgesia, and mood effects such as dysphoria or euphoria.11

Cannabis possess primary adverse effects on the CNS and respiratory systems.10,15 However, unlike opioids, cannabis has never been linked to acute overdose toxicity or death when used alone.8 This, however, does not imply universal safety.8 For example, inhalation injury has been repeatedly displayed in cannabis users when the substance is smoked. There is an exponential increases in serum carboxyhemoglobin levels and tar retention in lungs in cannabis smokers as compared to tobacco smokers, due in large part to the nearly 70% greater exposure to carcinogens in cannabis vs cigarettes.5,10 Interestingly, this appears to be linked to the physiology of the user’s experience; longer periods of inhalation and breath holding are more likely to lead to lung damage, including chronic obstructive pulmonary disease and cancer.5,10 With the increase in carbon monoxide exposure with cannabis use, there is increasing risks for acute coronary syndromes including arrhythmia, cardiomyopathy, myocardial infarction, and even stroke.5,8,10

Draz et al reported evidence of coronary artery disease in young patients with history of cannabis use, even in the absence of known risk factors, such as diabetes mellitus, hyperlipidemia, or hypertension.8 It is therefore of greater clinical significance in those patients with known underlying heart disease.5 Cannabis use in pregnancy has been linked to derangements in fetal development and malignancies such as astrocytoma and rhabdomyosarcoma.10 Conversely, a large study reported no additional congenital defects in utero among mothers who reported occasional cannabis use during pregnancy.16    

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Vaping vs Smoking     

To reduce the risks associated with smoking cannabis, alternative methods of delivery for inhaling cannabis have been suggested. One such method is vaporization. Vaporizing cannabis is achieved by heating the herb to a high enough temperature to release the THC and other active components but not cause combustion.17 Therefore, a patient can get the active components of the medicinal cannabis without the harmful pyrrole compounds. 17 Carbon monoxide is still produced, but in significantly reduced amounts when compared to more traditional smoking.17 Respiratory conditions are subsequently diminished without pyrrole release, and there is a reported reduction in symptoms such as cough and phlegm production seen in vaporizer use vs smoking.18 

A study that surveyed nearly 7000 people who use cannabis monthly revealed that of those that vaporized the cannabis, 65.8% reported no concerning respiratory symptoms compared with 56.0% of those who smoked it.18 This data may not accurately depict the difference in respiratory effect between vaporizing vs smoking. Factors such as age, sex, the amount of cannabis used, and other respiratory irritants such as cigarette smoking were not accounted for in these statistics, making cause and affect inferences a challenge.18

While historically considered a more favorable method of delivery, there has been an emergence of e-cigarette, or vaping, product used-associated lung injury (EVALI). The Centers for Disease Control and Prevention (CDC) and Food and Drug Administrations (FDA) are discouraging people from using vaping products, particularly those containing cannabis, until the true cause of EVALI can be delineated.19,20 Since there release in 2007, e-cigarette use has exploded, especially among adolescent and young adults. Corresponding to the rise in use, pulmonary injury patterns have been observed in a much broader age demographic such as those as young as 13 and as old 72 years.20,21  While no one brand or chemical has been directly linked to EVALI, nearly 77% of those reported use of a THC containing compound in the 30-days prior to the onset of their lung injury.20