Taking THC together with medications that also slow blood clotting could increase the risk of bruising and bleeding. While generally considered safe, CBD can cause drowsiness, lightheadedness, nausea, diarrhea, dry mouth and, in rare cases, liver damage. Taking CBD with other medications that have similar side effects may increase the risk of developing unwanted symptoms or toxicity. In other words, taking CBD at the same time as over-the-counter or prescription drugs and substances that cause drowsiness, such as opioids, benzodiazepines (such as Xanax or Ativan), antipsychotics, antidepressants, antihistamines (such as Benadryl), or alcohol, can cause increased sleepiness, fatigue, and possibly accidental falls and accidents while driving.
You can also experience increased sedation and tiredness when consuming certain herbal supplements, such as kava, melatonin and St. Taking CBD with stimulants (such as Adderall) may cause a decrease in appetite, while taking it with metformin, a medication for diabetes, or with certain medications for heartburn (such as Prilosec), it may increase the risk of diarrhea. Delta-9-tetrahydrocannabinol (THC) and cannabidiol are pharmacologically active cannabinoids in marijuana that are metabolized by cytochrome P450 (CYP), 3A4; THC is also metabolized by CYP2C9, a liver enzyme.1 A pharmacokinetic study revealed that ketoconazole, a CYP3A4 inhibitor, nearly doubled the concentrations of THC and cannabidiol,2 and similar interactions could occur with other CYP3A4 inhibitors, such as macrolides and verapamil, increase the psychoactive effects of THC and dose-related adverse effects of cannabidiol (for example, in vitro studies indicate that THC and CBD have a limited capacity to inhibit the activity of CYP450 enzymes). A case report showed an increase in the response to warfarin in a patient who smoked 4 to 5 marijuana joints per week.
7 Smoking marijuana, but not by oral administration, has been shown to increase the metabolism of theophylline and chlorpromazine, with a reduction of approximately 50% in their plasma concentrations, 8 This is believed to be due to the induction of CYP1A2 by smoking more than 2 joints of marijuana per week.