DISCUSSION
This new finding of methylene blue as an effective treatment for
chemotherapy-induced oral mucositis in a pediatric patient outlines a
potential alternative analgesic therapy for this common adverse event of
cancer therapy, not explored before on this age population.
Methylene blue is a monoamine oxidase, nitric oxide synthase, and
guanylate cyclase inhibitor [9]. When methylene blue and dye with
biologic substrates are combined, they react with nucleic acids and
damage proteins and lipid membranes of organisms [10]. It is not
well understood how these properties translate to its analgesic
properties, but there are several clinical and in vitro findings
of methylene blue’s action on both peripheral and central neural
pathways [9]. Methylene blue has the unique property of temporarily
ablating nerve endings, which has been useful in the treatment of
intractable
pruritus
ani [11]. In patients with open lumbar diskectomy, its
anti-inflammatory mechanism has been shown to reduce lower back pain
after surgery [12]. Deng et al. found that an injection of methylene
blue within the disc for discogenic back pain led to decreased pain
scores at 3 and 6 months (p < 0.05) [13]. Our report now
adds to the literature on the therapeutic usefulness of topical
methylene blue.
Methylene blue comes in several different formulations, including
intravenous and tablet, and was most recently used in conjunction with
photodynamic therapy. Its diverse methods of administration make it a
prime anti-nociceptive agent for many types of patients and pain
complaints. Unlike other therapies for oral mucositis–related pain that
include the use of local anesthetics, this oral rinse formulation uses
only methylene blue and normal saline. Without the sensation-dulling
effect of local anesthetics, a patient’s sensation of taste can be
preserved and therefore encouraging oral intake. For the pediatric
population, this is paramount, as oral mucositis can lead to rapid
weight loss and poor nutritional status.
When used systemically (e.g. oral or parenteral) methylene blue is not
risk-free. Patients who are taking monoamine oxidase inhibitors,
selective serotonin reuptake inhibitors, or serotonin and norepinephrine
reuptake inhibitors are advised to use methylene blue with caution,
given the increased risk of life-threatening serotonin syndrome [14]
[15]. In addition, when given as an oral capsule may cause nausea,
upset stomach, diarrhea, vomiting, or bladder irritation [16].
Despite its potential risk when used systemically, methylene blue
appears to be safe and well tolerated in its oral rinse or topical
formulation.