Can vitamin C be used as an adjuvant for managing postoperative pain? A short literature review.

LETTER TO EDITORS

Postoperative pain management remains a major challenge for health care providers [1,2]. Despite huge technological advances in pain management, many researchers have documented that unrelieved pain remains common after surgeries. Although most surgical patients receive some form of postoperative pain management, it is estimated that up to 75% of patients do not achieve adequate pain relief postoperatively [2,3]. A study conducted by Apfelbaum et al. showed that approximately 80% of the patients experienced pain after surgery. Of these patients, 86% had moderate, severe, or extreme pain [3]. Poorly controlled postoperative pain may result in clinical and psychological changes such as atelectasis or pneumonia, myocardial infarction, coronary ischemia, poor wound healing, insomnia and demoralization. These changes cause increase in morbidity and mortality and patients' health-care costs while impoverishing quality of life and patient satisfaction [4,5]. The major goal in the management of postoperative pain is to minimize the dose of medications to lessen the side effects while still providing adequate analgesia, because side effects of commonly used pain medications are known to be the reasons that could lead to inadequate postoperative pain treatment. This goal is best accomplished with multimodal analgesia [6,7]. One agent that can exert antinociceptive and pain reducing effects is vitamin C [8,9].

Vitamin C (ascorbic acid) is water-soluble, found throughout the body and is especially highly concentrated in the brain [10]. Vitamin C is necessary for normal growth, development and the formation of collagen which is important for the healing of skin and scar tissue, blood vessels, ligaments and tendons [7]. In addition, vitamin C has antioxidant and neuroprotective properties [10,11]. Moreover, it has been proven that the plasma vitamin C concentration decreases after surgery and the requirement for vitamin C increases in surgical patients, possibly due to greater demand caused by increased oxidative stress [12]. Regarding the effect of vitamin C on acute pain, a result from a recent study with the aim to evaluate the potential role of vitamin C in reducing acute pain after laparoscopic cholecystectomy showed that supplementation with oral vitamin C significantly decreased morphine consumption after surgery [7]. Two studies by Zollinger et al. [13] and Besse et al. [14] with the aim to assess the effectiveness of vitamin C in the prevention of complex regional pain syndrome after orthopedic surgery revealed that vitamin C significantly reduces the prevalence of complex regional pain syndrome. Additionally, a case report by Byun et al. [15] showed that in the case of postherpetic neuralgia, which did not respond to conventional therapy such as analgesics and nerve block, an intravenous infusion of vitamin C resulted in an immediate reduction in pain which is in agreement with the result by Chen et al. [16] who reported that an infusion of vitamin C was effective in zoster associated neuralgia. The antinociceptive effect of vitamin C and its site of action are not well understood; however, vitamin C has several potential functions, including antioxidation and neuromodulation, which may play an important role in pain relief [7]. Because vitamin C is water soluble and easily excreted in the urine, supplementation with high doses has little adverse effect when administered either orally or parenterally [12].

In summary, because of the reduction in vitamin C concentration after surgery and the modest evidence for vitamin C's antinociceptive effect and role in postoperative pain relief, further clinical trials are warranted to determine its potential effect on postoperative pain, as well as its optimal doses and routes of administration.