Analgesic effects of rosemary essential oil and its interactions with codeine and paracetamol in mice

The use of herbal medicinal products in the management of pain has been increasing steadily in recent years, often in combination with conventional analgesics, which can induce significant interactions. In traditional medicine, rosemary was used as mild analgesic, for relieving renal colic pain and dysmenorrhea. The aim of our study was to examine analgesic effects of rosemary essential oil and its pharmacodynamic interactions with codeine and paracetamol in mice.

The identification and quantification of chemical constituents of the essential oil isolated from air-dried aerial parts of rosemary were carried out by GC/FID and GC/MS. The hot plate test was performed on NMRI mice by placing them individually on hot plate and assessing their response to the thermal stimulus.

In this research, we identified 29 chemical compounds of the studied rosemary essential oil, and the main constituents were 1,8-cineole, camphor, and α-pinene. Administration of investigated essential oil increased significantly the latency time of animal response to heat-induced pain between 20th and 50th minute of the test, when compared to saline-treated group. Rosemary essential oil in the dose of 20 mg/kg was shown to be more efficient than in the dose of 10 mg/kg, in combinations with both codeine and paracetamol.

Our findings support the use of rosemary in the management of pain and indicate a therapeutic potential of rosemary essential oil in combination with analgesic drugs. The mechanisms involved in analgesic effects of rosemary essential oil and the potential influence on cytochromes and drug metabolism should be more in-depth investigated.