- Black Pepper (Piper nigrum, Piperaceae)
- Analgesic Properties
In Chinese medicine, black pepper (Piper nigrum, Piperaceae) is known to warm the body. Studies have also indicated that the essential oil of black pepper has anti-inflammatory effects. In particular, linalool, a monoterpene, is one component of black pepper essential oil that has demonstrated analgesic properties in preclinical studies. Little is known about black pepper essential oil beyond these effects. The aim of this randomized, double-blind, placebo-controlled trial was to evaluate the analgesic properties of black pepper essential oil in patients experiencing pain.
Patients were recruited from the physiotherapy unit at the Hospital-School of the University Fernando Pessoa in Porto, Portugal, between May 2015 and July 2015. Patients included in the study were 18 years and older, presenting with pain, and available for the study period. Patients were excluded if they were using pain medication 8 hours before the study period, were pregnant or nursing, had active infections in the superior respiratory tract, or were consuming medication that could interfere with the olfactory system (e.g., quinolones).
A total of 54 patients were randomly divided into 2 different groups and provided identical-looking vials containing either the experimental oil (group A, n = 25) or the placebo oil (group B, n = 29). Patients in group A inhaled the black pepper essential oil (manufacturer unknown), while patients in group B inhaled sesame (Sesamum indicum, Pedaliaceae) oil (manufacturer unknown), both for 15 minutes. Before and after the treatment, patients were provided a questionnaire where they indicated the intensity (scale of 0 to 10) and location of the pain.
The mean patient age in this study was 39.9 ± 15.3 years (age range, 18-73 years). There were a total of 35 (64.8%) females and 19 (35.2%) males in this study. More females were in group A (80%, n = 20) than in group B (51.7%, n = 15). In this study, the area of pain was divided into 3 different caloric regions based on the principles of Chinese medicine. Overall, the patients presented with pain in the upper caloric region (upper chest area, 37%), in the middle caloric region (middle abdomen, 3.7%), the lower caloric region (area between the navel and the feet, 53.7%), and both the upper caloric and middle caloric regions (5.6%). In particular, group A presented with pain in the upper, middle, lower, and upper and lower caloric regions (40%, 8%, 40%, and 12%, respectively). Group B presented with pain in the upper and lower caloric regions (34.5% and 65.5%, respectively).
The median value of pain intensity before inhalation was 6.37 for all patients, 6 for group A, and 7 for group B (for all groups, the minimum value [min] was 3 and the maximum value [max] was 10). There were no significant differences between the 2 groups. The median value of pain intensity after inhalation of the essential oil was 4 for all patients (min, 0; max, 10), 3 for group A (min, 0; max, 8), and 6 for group B (min, 3; max, 10). There was a significant difference found between the 2 groups (P = 0.00) after inhalation, which was further supported by the lower mean rank values for A (17.70) compared to the mean rank values for B (35.95).
Consistent with preliminary research on the volatile constituents of black pepper, the authors of this study found that inhalation of black pepper essential oil resulted in a significantly lower pain intensity score than the placebo oil. Due to the small sample size, pain region variability, and unbalanced gender of this trial, more studies will have to be conducted to not only confirm the study results but also to assess differences between gender and pain regions. The results of this study indicate that black pepper essential oil may be an untapped resource for pain management.
Costa R, Machado J, Abreu C. Evaluation of analgesic properties of Piper nigrum essential oil: a randomized, double-blind, placebo-controlled study. World Journal of Traditional Chinese Medicine. 2016;2(2):60-64.