Citrus medication relieves dry mouth in cancer patients

Natural citrus oil from oranges, lemons and limes has proven highly effective in combating dry mouth, and when combined with a new lipid-based formula, new research shows it can be effective without significant side effects.

Developed by the University of South Australia in collaboration with Stanford University School of Medicine, this world-first formula uniquely combines limonene (citrus essential oil) with a lipid-based drug delivery system to treat dry mouth (xerostomia), a common side effect of radiation therapy.

The new formulation demonstrated 180-fold better solubility compared to pure limonene in laboratory experiments and increased relative bioavailability by more than 4000% compared to pure limonene in preclinical studies.

Dry mouth is the most common side effect after radiation therapy for head and neck cancer, affecting up to 70% of patients due to damage to the salivary glands. It can lead to difficulty speaking and swallowing, significantly reducing quality of life.

Limonene has a protective effect on saliva production during radiation therapy, but due to its poor solubility, large doses are required to achieve the effect, causing digestive disturbances, abdominal discomfort and an unpleasant ‘citrus burp’.

Lead researcher Professor Clive Prestidge says the new combination of limonene and UniSA lipids creates a “super-soluble” remedy that reduces dry mouth at a lower dose and without unpleasant side effects.

“The therapeutic properties of limonene are well known. It is used as an anti-inflammatory, antioxidant and mood-enhancing agent, and can also improve digestion and bowel function. But despite its widespread use, its volatility and poor solubility limit its use as an oral agent,’ says Prof. Prestidge. – Because limonene is an oil, it forms a film on top of the stomach contents, causing severe pain and discomfort”.

“Our new formula combines limonene with beneficial fats and oils – called lipids – to create a super-soluble compound that is easily absorbed by the body with reduced unpleasant side effects. This increases the distribution of limonene in the stomach, enhances absorption and controls biodistribution – all while increasing the patient’s saliva production and reducing dry mouth.”

According to co-investigator Dr. Leah Wright, the drug has the potential to significantly improve the quality of life for cancer patients and others who suffer from dry mouth.

“Cancer patients undergoing radiation therapy and other treatments regularly experience dry mouth, which not only prevents them from swallowing comfortably, but can have other negative and potentially life-threatening consequences.”

Dr. Leah Wright, Co-researcher, University of Adelaide

Although limonene can be taken orally by itself, it is poorly tolerated, especially by those who suffer from dry mouth. In addition, its poor absorption prevents it from effectively reaching the salivary glands, the target site.

This innovative and very effective limonene lipid formulation could be a simple and effective solution to dry mouth, providing cancer patients with long-lasting relief and comfort, improved oral health and a better quality of life during a difficult period.

Clinical trials of the new formula are ongoing and further milestones will be announced shortly.