The effects of Lavandula angustifolia essential oil on analgesic effects and percutaneous absorption of naproxen sodium gel; an in vivo and in vitro study.

The percutaneous bioavailability of naproxen is low and several technologies have been utilized to overcome the problem. Although, some studies have reported the permeation-enhancing properties of natural essential oils, no research has reflected the effectiveness of Lavandula angustifolia essential oil (LAEO) on increasing the percutaneous absorption of naproxen sodium from a topical gel. Therefore, the present study was designed to investigate whether LAEO increased the percutaneous absorption and the analgesic effects of naproxen sodium topical gel. In the present study, naproxen topical gel was formulated using carbopol 940 (a gelling agent) and several vehicles such as PEG 400, ethanol, and water and the properties of gels were measured. Percutaneous absorption-enhancing properties of LAEO were measured too. Based on our data, the essential oil-containing formulation of naproxen represented greater penetration into (222.19 ± 24.87 vs. 107.65 ± 6.38 μg/cm 2 ), and also across (22.07 ± 4.42 vs. 13.14 ± 2.87 μg/cm 2 ) skin layers compared to the naproxen gel. Additionally, a significant analgesic property was observed in the naproxen topical gel containing 0.5% essential oil during both first and late phases of formalin test, as well as the late phase of tail-flick test. It could be concluded that LAEO significantly enhanced naproxen percutaneous absorption and also its analgesic effects.