Does cannabis have any bad interactions with pharmaceutical meds?
Medical cannabis is becoming more common across the United States in the treatment of diseases as far ranging as cancer and epileptic seizures, to pain relief and anti-anxiety. But how do cannabis or purified cannabinoid preparations fare when taken in combination with traditional pharmaceutical preparations?
Unfortunately, not a lot of research exists that has tested these questions clinically. This is due to the regulatory hurdles currently in place by the DEA classification of cannabis and cannabinoid isolates as Schedule I compounds, meaning they have no medicinal value and are too dangerous to be administered to patients without the direct supervision of a physician. It’s almost impossible for hospitals or universities to carry out a clinical study on cannabis, which translates to a dearth of published data on the topic of medication crossover.
However, some research has been done. In the past twenty years, and with large amounts of lay-people encouragement based on anecdotal evidence,a sizeable number of clinical and translational research studies have been carried out to definitively establish the potential of cannabinoids in the treatment of epilepsy. [1,2] It was determined that cannabidiol was the largest mediator of anti-seizure effects.  Among the clinical studies performed, a group at Massachusetts General Hospital wanted to see how the new cannabis treatment might affect the medication regimen their pediatric patients were on to combat seizures.  This study found that the CBD isolate Epidiolex® could safely be used in combination with currently available anti-seizure medications.
Cannabis has also become a mainstay supportive therapy in easing treatment-induced nausea and vomiting in the oncology ward. A 2014 WebMD poll indicated that 82% of oncologists surveyed believe that patients should have access to cannabis to make their cancer treatment feel less awful.  To support these findings, a 2007 clinical study by Engels et al showed no cross-over between oral cannabinoid administration and mainstay chemotherapy agents Irinotecan and Docetaxel. 
Finally, cannabinoids seem to have no mal-effects when it comes to HIV. A study undertaken to examine the effects of cannabis on viral load (quantity of virus in a defined volume) and T-cell (subtype of white blood cell) counts, as well as levels of anti-retroviral medications of immunocompromised patients found no substantial differences between the experimental and control group.  The medicinal use of cannabis was not problematic for this population of patients, either.
The main take away from this article is that not a lot of research has really been done, and the verdict on any interactions between cannabis and most pharmaceuticals is definitely still out until the scientific community can have its day in the clinic and in the lab.
- Friedman, Daniel, and Devinsky, Orrin. “Cannabinoids in the Treatment of Epilepsy”. N Engl J Med. 2015; 373: 1048-1058[Times cited = 150, Journal impact factor = 79.258]
- Szaflarski, J.P., and Bebin, E.M. “Cannabis, cannabidiol, and epilepsy–from receptors to clinical response”. Epilepsy Behav. 2014; 41: 277-82[Times cited = 91, Journal impact factor = 2.061]
- Devinsky, Orrin, et al. “Cannabidiol: Pharmacology and Potential Therapeutic Role in Epilepsy and Other Neuropsychiatric Disorders”. Epilepsia. 2014; 55(6): 791-802[Times cited = 395, Journal impact factor = 4.706]
- Geffrey, Alexandra L., et al. “Drug–drug interaction between clobazam and cannabidiol in children with refractory epilepsy”. Epilepsia. 2015; 56(8): 1246-51[Times cited = 148, Journal impact factor = 4.706]
- Rappold, R. Scott. Legalize Medical Marijuana, Doctors Say in Survey. WebMD. Published April 2, 2014. Accessed Feb 14 2019
- Engels, Frederike K., et al. “Medicinal Cannabis Does Not Influence the Clinical Pharmacokinetics of Irinotecan and Docetaxel”. The Oncologist. 2007; 12: 291–300[Times cited = 46, Journal impact factor = 5.306]
- Abrams, D.I., et al. “Short-term effects of cannabinoids in patients with HIV-1 infection: a randomized, placebo-controlled clinical trial”. Ann Intern Med. 2003 Aug 19;139(4):258-66[Times cited = 244, Journal impact factor = 19.384]
Image Citation: The Cannabis Reporter