Know the Patient’s History Before Recommending Cannabis
Always review absolute contraindications before discussing strains or symptom management.
Contraindications include:
- Recent heart attack or existing heart disease
- Arrhythmia (irregular heart rhythm, e.g., atrial fibrillation)
- Pregnancy or planning pregnancy, breastfeeding
- Age <25
- Personal or family history of mental illness (schizophrenia, bipolar disorder, psychosis)
- History of drug or alcohol abuse
- Chronic lung disease (emphysema, chronic bronchitis, asthma)
Risks:
- Smoking cannabis after a recent heart attack increases cardiovascular risk.
- Cannabis can trigger arrhythmias, lower blood pressure, and increase heart rate — leading to dizziness, fainting, or even stroke.
- In pregnancy, cannabis may impair cognition, reasoning, and behavior in the child.
- Chronic use worsens respiratory symptoms and infection risk in patients with lung disease.
- Heavy use can worsen or precipitate mental illness, including psychosis and suicidal ideation.
- Sedation risk is higher when combined with alcohol, benzodiazepines (Xanax, Valium), or other CNS depressants.
Polypharmacy and Drug–Drug Interactions
Older adults often take 5+ medications (polypharmacy) and are at higher risk for cannabis–drug interactions. Clinicians should monitor closely for adverse effects and altered drug levels.
Indications for Cannabis
Not all are FDA-approved, but potential therapeutic areas include:
- Chemotherapy-induced nausea and vomiting (CINV)
- Chemotherapy-induced neuropathy
- Anorexia/cachexia (weight loss in advanced cancer, AIDS)
- Epilepsy (certain pediatric syndromes)
- Muscle spasms from multiple sclerosis (MS)
Precautions and Warnings
- Older adults: Slower metabolism, increased risk of dizziness, falls, memory impairment.
- Youth <25: May develop impaired problem solving and thinking.
- Lung disease: Smoking can worsen breathing, reduce function, and increase infection risk.
- Liver/kidney disease: Slower metabolism may prolong effects (e.g., Hepatitis C).
- Pregnancy and breastfeeding: Cannabis crosses the placenta and is secreted in breast milk.
- Mental illness: Avoid THC-heavy products in those with psychosis, schizophrenia, or bipolar disorder.
- Substance use disorder: Higher risk of cannabis use disorder.
- Heart/brain disease: Patients with prior heart attack or stroke should avoid cannabis.
- Driving and operating machinery: Cannabis impairs alertness and judgment.
- Drug screening: Positive cannabis screens may persist for weeks, affecting employment.
- Hypersensitivity: Cannabis can cause allergic-like reactions (rash, watery eyes, cough, runny nose).
References
- Blesching U. The Cannabis Health Index. Cannabis and heart attack. p.121.
- Blesching U. The Cannabis Health Index. Cardiac Arrhythmias. p.118.
- Huizink A.C. Prenatal cannabis exposure and infant outcomes. Prog Neuropsychopharmacol Biol Psychiatry. 2014;52:45-52.
- The Health Effects of Cannabis and Cannabinoids. NASEM. Respiratory Disease, pp.192-193.
- The Health Effects of Cannabis and Cannabinoids. NASEM. Cardiometabolic Risk, p.166.
- The Health Effects of Cannabis and Cannabinoids. NASEM. Mental Health, pp.289-331.
- Government of Canada. Cannabis and the cannabinoids: Information for health care professionals.