Side Effects and Drug Interactions

Unlike pharmaceutical medications, CBD has no lethal dose.

Safety: A review paper on the Safety and side effects of CBD by the NCBI suggests that controlled CBD administration is safe and non-toxic in humans and animals. It also does not induce changes in food intake; nor does it affect physiological parameters like heart rate, body temperature or blood pressure. Also, according to this review paper, “high doses up to 1,500 mg/day of CBD are reportedly well tolerated in humans.”

There are very few known side effects of CBD. The above review paper mentions the following as potential side effects:

1. Inhibition of hepatic drug metabolism

CBD can potentially inhibit the activity of the liver enzyme called cytochrome P450. This family of enzymes metabolizes nearly 60% of the pharmaceutical drugs used to treat humans. If one takes extremely high doses of CBD, this can temporarily neutralize the activity of P450 enzymes and thus alter the way drugs are metabolized inside the body. In particular, CBD can regulate blood pressure effectively enough to warrant reduction in HBP medications.

To put this in perspective, though, eating a portion of grapefruit would have a similar effect on the P450 liver enzymes. Drug interactions should be viewed as a minor side effect of cannabidiol. As a precaution, if you are taking pharmaceutical drugs and plan to take CBD, you should discuss any potential complications regarding reduced P450 enzyme activity with your doctor and/or pharmacist. In states that have legalized medical marijuana and CBD for many years, this potential interaction with the P450 has not proven to be clinically significant.

The only documented serious concern has been noted in epilepsy patients taking a medication clobazam, an anticonvulsant. A majority of these patients needed to have their dose of clobazam reduced due to side effects. A 2015 report concluded that CBD is safe and effective for treatment of refractory epilepsy in patients receiving clobazam, but emphasized the importance of monitoring blood levels of clobazam in those patients using CBD.

2. Dry mouth

Another reported side effect of CBD administration is an unpleasant dry sensation in the mouth. This effect seems to be caused by the involvement of the endocannabinoid system in the inhibition of saliva secretion. A study published by Argentinian researchers back in 2006 showed that cannabinoid receptors (type 1 and 2) are present in the submandibular glands which are responsible for producing saliva. The activation of these receptors alters the salivary production, leading to mouth dryness (also referred to as “cotton-mouth”). In addition, the presence of an anti-inflammatory terpene called carene, commonly found in Hemp, can contribute to reduced saliva production. Dry mouth will pretty much just make you thirsty.

3. Increased tremor in Parkinson’s disease at high dose CBD

Early research suggests that CBD taken in high doses may worsen tremor and muscle movement in Parkinson’s disease sufferers. Yet there are also studies that suggest that cannabidiol is safe and well-tolerated by patients affected by this condition. If symptoms do worsen, reducing the dose should reduce this potential side effect. Parkinson’s disease sufferers should consult their doctor before taking CBD and also begin any regimen by taking smaller doses.

4. Low blood pressure

Higher doses of CBD oil can cause a small drop in blood pressure , usually within a few minutes of the CBD entering your system. This drop in blood pressure is often associated with a feeling of lightheadedness. If you are taking medication for blood pressure, you should consult your doctor before taking CBD.

5. Lightheadedness

This can be caused by the drop in blood pressure that can affect those using higher doses. This side effect of CBD is temporary and can often be resolved by drinking a cup of coffee or tea.

6. Drowsiness

In higher doses, CBD can cause drowsiness. If you are affected in this way, you should not operate machinery or drive a vehicle. In most cases, however, CBD is a wake-inducing agent. Alternatively, high doses of CBD can be used as a very effective sleep aid, activating serotonin and melatonin receptors, raising dopamine levels during sleep, and promoting photoentrainment (the tying of circadian rhythm to sunlight cycles).