Researchers and medical practitioners alike are eager to discover what conditions medical cannabis can help treat.
One important area of research could mean the difference between medical cannabis being a beneficial treatment option and being a detriment to a patient’s health is that of drug interactions. When treating certain conditions, medical cannabis will likely be used in conjunction with other treatments. In some cases, it might be used to treat a patient with several conditions.
Knowing how cannabis interacts with various other medications is thus important.
Here are five medical cannabis drug interactions physicians should know before they authorize or recommend medical cannabis to any patient.
The Effects of Medical Cannabis Could Be Increased by Certain Drugs
Medical cannabis contains delta-9 tetrahydrocannabinol, or THC. This compound is one of the best-known and best-studied cannabinoids. It occurs in varying concentrations in different strains and preparations of medical cannabis.
THC is responsible for many of the effects of cannabis, including drowsiness, a feeling of relaxation, and even hunger. It can also increase some psychological effects, such as paranoia or anxiety, thanks to its psychoactive properties.
THC is oxidized by CYP mixed function oxidases, and so substances that decrease the availability of these oxidases could increase the bioavailability of THC. In turn, this could increase the chances of experiencing THC-related side effects.
Medications that would increase a patient’s chances of experiencing THC side effects include some anti-depressants like fluoxetine, proton pump inhibitors like cimetidine, and macrolides like clarithromycin. Antimycotics, calcium antagonists, HIV protease inhibitors, amiodarone, and isoniazid are also implicated.
Some Drugs May Decrease the Bioavailability of THC
Conversely, some medications, like phenobarbital, rifabutin, primidone, and Saint John’s Wort may actually decrease the bioavailability of THC. These drugs accelerate the metabolization of THC in the body by increasing the availability of CYP oxidases. THC is thus oxidized faster.
While this may sound like good news as it reduces the chances of a patient experiencing THC-related side effects, it could be detrimental in a therapeutic context. If the patient is trying to achieve symptom relief, they may need to exceed the recommended dose as the effectiveness of medical cannabis is reduced.
Medical Cannabis Could Increase the Bioavailability of Some Drugs
Medical cannabis can also affect how other medications are metabolized in the body. THC, CBD, and CBN are all known to inhibit some CYP isozymes, including CYP 1A1, CYP 1A2, and CYP 1B1. By limiting the availability of these enzymes, these cannabinoids increase the bioavailability of substances that would be metabolized by them.
These drugs include phenacetin, granisetron, dacarbazine, and flutamide. Patients taking these medications could find their effectiveness enhanced. Alternately, toxicity may be achieved at a much lower dosage than expected.
Physicians should exercise caution when authorizing medical cannabis for use in patients who also use these medications.
Cannabis Interacts with Opioids
One of the hopes for medical cannabis is that it may be able to help combat the current opioid crisis. Many patients have self-reported results from the combination of medical cannabis and opioids, suggesting cannabis could help them reduce or eliminate their dependence on opioids.
Physicians must exercise caution here, as cannabinoids and opioids are known to interact. Fentanyl, oxycodone, and related opioids appear to both prolong and intensify the “high” patients experience when taking medical cannabis.
Antipsychotic medications such as clozapine may also interact with cannabis in a similar way. Some opioids, such as morphine, do not appear to interact with cannabinoids as the above examples do.
What does this mean? As always, physicians must be prudent and examine patients on a case-by-case basis. Drug interactions can have serious consequences, so caution must be exercised to ensure patients stay safe when taking medical cannabis.
Other Drug Interactions to Consider
CBD can also interact with clobazam and other antiepileptics. It is important to always talk to a doctor about these potential interactions. Also, using cannabis can lower blood sugar, so diabetics may want to check their blood sugars more often when first starting cannabis. Using cannabis with other sedating medications such as benzodiazepines or sleeping pills may also lead to further sedation and increased risks of car accidents or falls.