CBD Patches

Introduction

Transdermal CBD patches are medicated strips that release cannabinoids through the skin into the bloodstream when stuck on specific areas of the skin.

The WHO reports that 70% of deaths worldwide are due to non-communicable diseases. That collectively includes cardiovascular diseases, cancer, chronic respiratory diseases, and diabetes. Besides, several other conditions that branch out of them. That said, what are the driving causes of these chronic disorders?

Human habits such as tobacco use, alcohol abuse, unhealthy diet, and lack of physical activity are the root causes of these conditions. But to diagnose, treat, cure, or prevent these severities comes with a lot of challenges. In particular conventional drug delivery systems such as oral tablets, capsules, or intravenous administration do not completely address pain and inflammation. As a result, they are ineffective and come with adverse side effects. 

Therefore there is a growing need to improve efficacy and optimize bioavailability.

Thanks to new drug delivery systems developed to deliver desired cannabinoids through oral, dermal, and implantable systems to deliver more effectively.

For people who choose cannabis-based therapies, or CBD products, CBD patches are yet another option. Transdermal delivery of cannabidiol helps in a controlled and sustained release that allows the CBD to target directly to the tissues.

In sum, this article aims to address some common questions about CBD patches, their functions, and effects.

What are CBD patches?

“Transdermal Drug Delivery, (TDDS) a self-contained, discrete dosage form known as patches.” defines a 2017 study¹ 

In appearance, a CBD patch is similar to a band-aid. ( probably the size of your palm) And may come in a square or circular shape. These CBD patches are made from thin layers of plastic, infused with CBD, coated with adhesive and reagents that enhance skin penetration. This transdermal technology supports delivering definite doses of the cannabinoid directly into the bloodstream through the skin.

A 2008 study² discusses that the design of most transdermal patches is more or less similar.

The drug is stored in a reservoir where one side is encased in a leak-proof backing and the other adhesive side contacts the skin. According to the manufacturer, the patch designs might vary and can have two or up to four layers including leak-proof impermeable backing membrane, drug reservoir, semi-permeable membrane, and the adhesive layer. Such designs are suitable to contain liquid or gels.

Transdermal patches are long-lasting as they are sweat and waterproof. As a result, CBD delivery is consistent and effective.

CBD patches are available in different potencies and may contain full-spectrum, broad-spectrum or isolated CBD depending on the manufacturer.

Types of Patches

Reference from two studies, a 2007 study³ and a 2011 study⁴ elaborate on the classification of different patches and their functions. 

Matrix patch	Reservoir patch or Membrane controlled system	Drug-in-adhesive patch
A polymer matrix holds and controls the  release of the drug.	The drug is stored and released through a liquid reservoir behind a leak-proof rate-limiting membrane.	The drug is directly incorporated into the adhesive layer.
Such patches are used when the drug and the transdermal adhesive are not compatible or soluble.		Such patches are capable of readily permeating the skin. Example: lidocaine, nitroglycerine, and nicotine.
The active ingredient is distributed evenly throughout the patch.	Reservoir patches give tighter control of delivery rates.
Less risk of accidental overdose and offers less potential for abuse than the reservoir system.	Risk of sudden release of drug into the skin and overdose, as a larger area of skin is exposed for drug absorption.

How to use a CBD patch?

• Using a CBD patch is as simple as it looks. But to deliver CBD effectively into the system, choosing an appropriate area of your skin is the first step.
• Spot the area of pain and try to apply the patch close to the pain area. 
• Avoid bony areas or the elbow part that has more thick layers of skin.
• A CBD patch applied to a venous part of the body allows CBD to penetrate the skin readily, as the molecules get in close contact with a large part of the skin. Thereupon, this transdermal delivery route ensures maximum bioavailability of CBD into the bloodstream.
• Below the neck behind the ear, front portion of your foot, behind the ankle, wrist, shoulders, in between biceps and triceps, thigh, calf muscle, and lower back are effective spots that could sense relief quickly.
• Gently wipe the area where you want to apply the patch with an alcohol swab before you stick the patch.
• Peel the outer sheet and apply the patch. 

Suggested reading: CBD for muscle spasms.

How do CBD patches work?

In short, as soon as a CBD patch is attached to the skin, a series of chemical reactions follow. The body heat releases the CBD molecules and other ingredients contained in the patch. As these molecules get released, the skin begins to absorb them and head to the bloodstream. 

Now, let us try to understand in detail.

A 2011 study⁴ elaborates that a patch consists of the drug, release liner, adhesive, membranes, backing layer and other ingredients. 

• The release liner seals the area of the formulation to control the release of the drug. 
• The backing layer is a protective covering for the drug it holds. It raises the hydration level of the outermost layer of the skin, SC( stratum corneum).
• The adhesive keeps the patch firmly attached to the skin throughout use. 

The 2007 study³ explains, 

• Once the patch is attached, a drug concentration gradient gets established, and through it, the drug begins to move to the skin. ( Depends on the type of patch) 
• The outermost layer of the skin SC establishes a reservoir,
• The drug further moves to the other layers of the skin. And it gets absorbed into the network of blood vessels, which transports the drug for systemic circulation.

Benefits of transdermal delivery of CBD patches.

• In general, the transdermal route of administration of CBD products is discreet and easy to use. 
• It can be easily self-administered.
• A CBD patch is a need-based cannabinoid delivery. When not necessary, it is easier to remove.
• The 2018 study⁵ points out that absorption in oral routes is slow, erratic, and variable. But transdermal route eliminates the first-pass metabolism or the gut processes. 
• Hence patch delivers improved bioavailability. 
• Equally important, taking CBD through the transdermal route facilitates a steady release of cannabidiol over a longer duration. At the same time, the risk of higher drug peak concentrations gets diminished.  
• Topical routes are best suited for localized pain or symptoms. For instance, in arthritis, peripheral neuropathic pain, or dermatological conditions. 
• CBD patches provide positive effects in decreasing pain-related conditions including, pain caused by inflammation, localized pain, muscle spasms, multiple sclerosis, chemotherapy, lower back pains, injury, etc. 
• A 2015 study⁶ concludes that topical CBD application has therapeutic potential in relieving arthritis pain-related behaviours and inflammation without evident side-effects.
• A 2017 study⁷ states that the therapeutic value of many drugs could be enhanced through this method, as it eliminates all problems associated with drug-like lower absorption, GI irritation, decomposition due to hepatic first-pass metabolism. 

Disadvantages of transdermal delivery

A 2017 study⁸ points out the possibility of the low permeability of certain substances on the skin. 

We are aware that the human skin has low permeability. Because the skin acts as a protective barrier that does not allow easy absorption of a substance transdermally. 

Reference from a 1997 study⁹ on the permeability barrier of the skin, is noteworthy at this point. It states that the resistance of the outermost layer of the epidermis makes the transdermal delivery of drugs difficult and impossible. 

But, contrasting to the above reference, another study asserts the possibility of penetration of drugs that could vary in different regions of the skin (such as the forearm, shoulder, scalp, back, abdomen, buttock, etc.)

A 2010 study¹⁰ reports that chemical enhancers increase the skin permeability to therapeutic drugs. It also adds that some of the commonly used enhancers combined with iontophoresis ( a process of transdermal drug delivery using voltage) are terpenes, fatty acids, glycerides, etc. 

Are patches a new form of drug delivery? What does the research say?

• According to a reference from a 2008 study¹¹ in the United States in 1979, a three-day patch containing scopolamine, a medication to treat motion sickness was approved. But the profile of transdermal delivery among the public heightened when nicotine patches got introduced a decade later.
• Today, this drug administration method gets applied in contraception, hormone replacement therapy, ultrasonic delivery for analgesia, and more. Examples of drugs delivered transdermally are estradiol, lidocaine, testosterone, estrogen, progesterone, and many other combination drugs.
• A 2015 study¹² traces the use of salves, ointments, and patches that contained plant, animal and mineral extracts as early as 3000BC in ancient Egypt Babylonian medicine. 

Conclusion

• Transdermal patches avoid gastrointestinal administration and first-pass metabolism. And provides more controlled release of drug and maintain constant blood plasma levels. For this reason, many users prefer this form of delivering cannabinoids into their system.
• Need for further investigations in several topics: efficacy of cannabinoid patches, risks involved, patient compliance, the interaction between oral and transdermal routes, and performance of the drug.
• Decide on the ideal dosage route of CBD that best suits you. study¹³ confirm that biological factors such as skin temperature, age, gender, ethnicity, skin hydration level, skin metabolism, etc affect absorption.
• CBD transdermal patches aid in managing pain, inflammation, skin conditions, localized pains, and more conditions. Interestingly, the applicability of patches in delivering desired drugs to patients undergoing psychiatric disorders is increasing reports a study¹⁴
• There is a need to provide impetus to develop cost-effective solutions for developing transdermal patches. Because currently, they are an expensive alternative to oral cannabinoids.

References

1. Sandeepthi et al, TRANSDERMAL DRUG DELIVERY: AN OVERVIEW  J. Global Trends Pharm Sci, 2017; 8(4): 4537 – 4541 [↩]
2. Prausnitz MR, Langer R. Transdermal drug delivery. Nat Biotechnol. 2008;26(11):1261-1268. doi:10.1038/nbt.1504 [↩]
3. Lyn Margetts, FRCA, Richard Sawyer, FRCA FIPP, Transdermal drug delivery: principles and opioid therapy, Continuing Education in Anaesthesia Critical Care & Pain, Volume 7, Issue 5, October 2007, Pages 171–176 [↩] [↩]
4. Singh I, Morris AP. Performance of transdermal therapeutic systems: Effects of biological factors. Int J Pharm Investig. 2011;1(1):4-9. doi:10.4103/2230-973X.76721 [↩] [↩]
5. Bruni N, Della Pepa C, Oliaro-Bosso S, Pessione E, Gastaldi D, Dosio F. Cannabinoid Delivery Systems for Pain and Inflammation Treatment. Molecules. 2018;23(10):2478. Published 2018 Sep 27. doi:10.3390/molecules23102478 [↩]
6. Hammell DC, Zhang LP, Ma F, et al. Transdermal cannabidiol reduces inflammation and pain-related behaviours in a rat model of arthritis. Eur J Pain. 2016;20(6):936-948. doi:10.1002/ejp.818 [↩]
7. Sandeepthi et al, TRANSDERMAL DRUG DELIVERY: AN OVERVIEW  J. Global Trends Pharm Sci, 2017; 8(4): 4537 – 4541 [↩]
8. Sandeepthi et al, TRANSDERMAL DRUG DELIVERY: AN OVERVIEW  J. Global Trends Pharm Sci, 2017; 8(4): 4537 – 4541 [↩]
9. Pirot F, Kalia YN, Stinchcomb AL, Keating G, Bunge A, Guy RH. Characterization of the permeability barrier of human skin in vivo. Proc Natl Acad Sci U S A. 1997;94(4):1562-1567. doi:10.1073/pnas.94.4.1562 [↩]
10. Longsheng Hu, Priya Batheja, Victor Meidan, Bozena B. Michniak-Kohn, CHAPTER 4 – Iontophoretic Transdermal Drug Delivery, Handbook of Non-Invasive Drug Delivery Systems, William Andrew Publishing,2010, Pages 95-118, ISBN 9780815520252 [↩]
11. Prausnitz MR, Langer R. Transdermal drug delivery. Nat Biotechnol. 2008;26:11:1261-1268. doi:10.1038/nbt.1504 [↩]
12. Pastore MN, Kalia YN, Horstmann M, Roberts MS. Transdermal patches: history, development, and pharmacology. Br J Pharmacol. 2015;172(9):2179-2209. doi:10.1111/bph.13059 [↩]
13. Singh I, Morris AP. Performance of transdermal therapeutic systems: Effects of biological factors. Int J Pharm Investig. 2011;1(1):4-9. doi:10.4103/2230-973X.76721 [↩]
14. Isaac M, Holvey C. Transdermal patches: the emerging mode of drug delivery system in psychiatry. Ther Adv Psychopharmacol. 2012;2(6):255-263 [↩]