A natural citrus oil from oranges, lemons, and limes is proving highly effective in relieving dry mouth, and when combined with a new lipid formulation, new Australian research suggests it may be effective without significant side effects.
Developed by the University of South Australia in collaboration with the Medical School at Stanford University, this world first formulation uniquely combines limonene (a citrus essential oil) with a lipid-based drug delivery system to treat dry mouth (xerostomia), a common side effect of radiotherapy.
The new formula demonstrated 180-fold better solubility than pure limonene in lab experiments and boosted relative bioavailability by over 4000 per cent compared to pure limonene in pre-clinical trials.
Dry mouth is the most reported side effect following radiotherapy for the treatment of head and neck cancer, affecting up to 70 per cent of patients due to salivary gland damage. It can lead to difficulty speaking and swallowing, significantly reducing quality of life.
Limonene has protective effects on saliva production during radiotherapy, but its poor solubility means high doses are needed to take effect, and these cause indigestion, abdominal discomfort and unpleasant ‘citrus burps’.
“The therapeutic benefits of limonene are well known,” lead researcher Professor Clive Prestidge said.
“It’s used as an anti-inflammatory, antioxidant, and mood-enhancing agent, and can also improve digestion and gut function. But despite its widespread use, its volatility and poor solubility have limited its development as an oral therapy.
“As limonene is an oil, it forms a film on the top of the stomach contents, causing significant stomach pain and discomfort.”
The team’s novel formulation combines limonene with healthy fats and oils—called lipids—to create a super-solubilising compound that the body can easily absorb with reduced uncomfortable side effects.
This increases the dispersion of limonene in the stomach, boosts absorption, and controls biodistribution—all while increasing a patient’s saliva production and reducing dry mouth.
“This inventive and highly impactful limonene-lipid formulation could provide a simple, effective oral solution for dry mouth, offering cancer patients long-lasting relief and comfort, improved oral health, and a higher quality of life during a difficult time,” co-researcher Dr Leah Wright added.
Clinical trials for the new formula are ongoing, with next steps to be announced soon.
