Cannabidiol is the major nonpsychoactive ingredient in cannabis. Cannabidiol demonstrates a range of effects that may be therapeutically useful, including anti-seizure, antioxidant, neuroprotective, anti-inflammatory, analgesic, anti-tumor, anti-psychotic, and anti-anxiety properties. Exact mechanism of action of cannabidiol is not known, but may include effects on the orphan G-protein-coupled receptor GPR55; the transient receptor potential of vanilloid type-1 channel; the 5-HT1a receptor; and the α3 glycine receptors. GW Pharmaceuticals successfully developed the world’s first prescription medicine derived from the cannabis plant, Sativex® (buccal spray containing delta-9-tetrahydrocannabinol and cannabidiol) now approved in over 29 countries outside of the United States for the treatment of spasticity due to Multiple Sclerosis. GW Pharmaceuticals is developing Epidiolex® (a liquid formulation of pure plant-derived cannabidiol) for certain rare and severe early-onset, drug-resistant epilepsy syndromes.

Bepotastine is a non-sedating, selective antagonist of the histamine 1 (H1) receptor. It belongs to the second-generation piperidine chemical class. It is a mast cell stabilizer and suppresses the migration of eosinophils into inflamed tissues. Bepotastine was approved in Japan for use in the treatment of allergic rhinitis and uriticaria/puritus in July 2000 and January 2002, respectively, and is marketed by Tanabe Seiyaku Co., Ltd. under the brand name Talion. It is available in oral and opthalmic dosage forms in Japan. The opthalmic solution is FDA approved since Sept 8, 2009 and is under the brand name Bepreve.

Capsaicin is a topical analgesic that is FDA approved for the treatment of neuropathic pain associated with postherpetic neuralgia. Capsaicin is most often used as a topical analgesic and exists in many formulations of cream, liquid, and patch preparations of various strengths; however, it may also be found in some dietary supplements. Capsaicin is a naturally-occurring botanical irritant in chili peppers, synthetically derived for pharmaceutical formulations. Capsaicin is an agonist for the transient receptor potential vanilloid I receptor (TRPVI), which is an ion channel-receptor complex expressed on nociceptive nerve fibers in the skin. Common adverse reactions include erythema, rash, pruritus, nausea.

Camphor is a bicyclic monoterpene ketone found widely in plants, especially cinnamomum camphora. Topically, camphor is used to relieve pain. It has been used to treat warts, cold sores, hemorrhoids, and osteoarthritis. It has also been applied topically as an analgesic and an antipruritic. It has been used as a counterirritant, and to increase local blood flow. Camphor has frequently been used topically to treat respiratory tract diseases involving mucous membrane inflammation. It is sometimes used topically to treat cardiac symptoms. Camphor is also used topically as an eardrop, and for treating minor burns. In inhalation therapy, camphor is used as an antitussive. Orally, camphor is used as an expectorant, antiflatulent, and for treating respiratory tract diseases. Today, most camphor is synthetic. It is approved by the FDA as a topical antitussive. Camphor is produced synthetically from the oil of turpentine. It has been used for centuries for its medicinal features, in religious rituals, and in cooking. It is no longer used as pesticide. In 1982, the US Food and Drug Administration restricted commercial products intended for medicinal use to contain <11% camphor.

Davasaicin is a synthetic derivative of capsaicin, developed at the Korea Research Institute of Chemical Technology. Davasaicin possesses very potent analgesic activity, demonstrated in several animal models, such as phenylbenzoquinone-induced writhing test, tail-flick test in mice and adjuvant arthritic flexion test in rats. When administered topically, davasaicin has an antipruritic effect in the mouse model.

Resiniferatoxin (RTX or RTX-107) is a vanilloid derived from a cactus-like plant (Euphoria resiniferous) and has anti-inflammatory activity. This compound is an agonist of the transient receptor potential vanilloid 1 (TRPV1). Resiniferatoxin produces analgesia by desensitizing the TRPV1 receptor. Findings of several studies have suggested a potential therapeutic use of the anti-inflammatory effect of resiniferatoxin. Phase I and II clinical trials have been completed or are underway, evaluating the safety and efficacy of resiniferatoxin in pain-related disorders such as osteoarthritis and cancers.

PAC-14028 was developed as a transient receptor potential vanilloid type 1 (TRPV1) antagonist. It is known that TRPV1 might be deeply associated with skin permeability barrier function, suggesting that modulation of TRPV1 might be beneficial for the skin disorders with barrier damages. Amorepacific developed a topical cream formulation of PAC-14028. This drug completed phase III clinical trial for the treatment of atopic dermatitis. In addition, PAC-14028 participated in phase II clinical trials to evaluate its safety and efficacy in seborrheic dermatitis and in rosacea. Moreover, PAC-14028 has been used in trials studying the treatment of pruritus.

SB-705498 is a selective vanilloid receptor-1 (VR1/TRPV1) antagonist developed by GlaxoSmithKline. The drug was tested in phase II of clinical trials for the treatment of pain (dental, rectal, in migraine) and rhinitis/cough. The development of the drug has been terminated by unknown reason (SB-705498 is no longer in GSK pipeline).

ABT-102 is a selective antagonist of transient receptor potential vanilloid type 1 (TRPV1), designed for the treatment of nociceptive pain. ABT-102 potently blocks multiple modes of TRPV1 receptor activation and effectively attenuates downstream consequences of receptor activity.