What Is Bioavailability?

Bioavailability is a measure of how much a substance is able to access the circulation and reach the target area, and it depends on absorption (how much the body takes in) and secretion (how much the body gets rid of).

Bioavailability can apply to food, pharmaceuticals, and to cannabis, as well as any substance taken into the body. 

Why is Bioavailability Important for Medical Cannabis?

According to cannabis experts, only about 10 to 14% of CBD products are actually absorbed into the system. Your body metabolizes and expels the rest. Because of the low amount being absorbed, it’s important that bioavailability of that percentage be as high as possible to ensure you’re getting the maximum effect from your CBD. In addition, CBD can be absorbed by the body better in fat than in water which is why CBD oil is one of the preferred method for administration. 

However, a study first published in 2007 titled “Human Cannabinoid Pharmacokinetics” reveals that, depending on smoking topography (depth of inhalation, number of puffs, and length of time between puffs) smoking can yield bioavailability from 20 to 60% for high-dose THC. The same review notes that oral administration (edibles, vapes, tinctures) are used more frequently for medical purposes because of the negative impact of cannabis smoke on the body. Bioavailability of oral administrations of THC were shown to be lower at 4 to 11 percent. A study by Wall et al was reported at 10-20% for oral THC. Participants were dosed with either 15 mg for women or 20mg for men with THC dissolved in sesame oil and contained in gelatin capsules.

Other Methods of Administration

Other methods of administration of THC include oromucosal (administration where a solution is given in the side of the mouth, into the space between the gum and the cheek. Typically using a spray and most frequently to treat the neuropathic pain associated with multiple sclerosis). Rectal administration using suppository formulations reduces first pass metabolism found in oral administration and increases bioavailability to 13.5% in a study or twice that or the oral route of administration due to higher absorption and lower first-pass metabolism.

Transcutaneous (delivered across the depth of the skin) and transdermal (application through the skin, typically with a patch) are additional routes for cannabinoid exposure that avoid first-pass metabolism and improve bioavailability in topical administration. Cannabinoids are highly “hydrophobic” and resist any moisture including that found in the skin. Using a dermal patch for transdermal delivery, delivery of Delta 8 THC was maintained for 48 hours. Not only do these delivery systems bypass what can be negatives effects from inhalation, it could also provide a more convenient delivery method. For example, a patient taking chemo treatment could place a dermal patch on and wear it for 48 hours or even several days after treatment to help reduce side effects from chemotherapy.

Cannabidiol Absorption

Cannabidiol (CBD) is a natural, non-psychoactive constituent of Cannabis Sativa. CBD has been reported to be neuroprotective, analgesic, sedating, anti-emetic, anti-spasmodic, and anti-inflammatory. The absorption of the cannabinoids regulates the effectiveness so, the more bioavailable the better. 

Here are some conclusions we can draw based on research and studies of bioavailability and cannabis:

  • Oral CBD — Has the lowest bioavailability, but can be improved with supplements like piperine, and taking the CBD along with fats.
  • Inhaled CBD — Offers a high-rate of absorption, but can be damaging to the lungs over time.
  • Transdermal CBD — Provides a slow and steady delivery, which offers advantages to people who need to maintain consistent levels of CBD in the blood.
  • Sublingual CBD — Such as oral sprays and sublingual drops have absorption rates similar to ingested CBD, while nasal inhalers have more rapid absorption rates comparable to inhaled CBD, without the downsides to the lung tissue.
  • Intravenous CBD (IV) — This is the fastest route of administration but also leaves the body the fastest. This method is reserved for medical professionals.

In addition to bioavailability, your state of health will influence which delivery forms may or may not work for you. Please contact The Healing Clinics and one of our knowledgable health professionals can help guide you to the best options for your specific health goals.