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Updated: Feb 20, 2026
Pupillometry to Assess Auditory Sensation in Guinea Pigs
Published on: January 6, 2023
Study of Methylene Blue Ototoxicity in the Guinea Pig
Sarah Belhassen1, Musaed Alzahrani1, Marc-Elie Nader1
1Division of Otolaryngology-Head and Neck Surgery, University of Montreal, Sainte-Justine University Hospital Center (CHU SJ), Montreal, Quebec, Canada.
Background:
Methylene blue is widely used in the medical field, especially as a blue dye for staining. It is also used as a photosensitizing agent in antimicrobial photodynamic therapy, which once photoactivated is effective for the eradication of several multi-resistant bacteria. The objective of this study was to investigate the ototoxic potential of methylene blue and precise its use in otology.
Methods:
It was a prospective animal study performed on guinea pigs in our tertiary medical center. We divided the animals into two groups: an experimental group and a control group, who underwent a series of three intratympanic (IT) injections. In the control group (n = 10), they received injections of gentamicin in one ear (positive control) and normal saline in the contralateral ear (negative control). The experimental group (n = 10) received injections of methylene blue in one ear, compared to injections of normal saline in the contralateral ear. We conducted auditory-evoked brainstem response (ABR) before and 1 week after the injection series. Once this is completed, the cochlea was dissected and caspase-3 was analyzed by immunohistochemistry.
Results:
The mean difference of hearing loss in the methylene blue group compared to normal saline was 1.50 dB, and it was not shown to be statistically significant (P = 0.688). For the positive control group, which received IT injections of gentamicin, the mean threshold of hearing loss difference for all the frequencies combined was 66.25 dB (P < 0.001). Furthermore, uptake of caspase-3 by immunohistochemistry (apoptotic marker) was negative in our group, which received injections of methylene blue.
Conclusion:
In light of our results, IT injections of methylene blue did not demonstrate an ototoxic potential. We recommend further studies to precise its use in the otologic field.
Insights
Methylene blue injections did not show ototoxicity in guinea pigs, indicating potential for otologic applications. Further research is recommended to confirm its safety and efficacy in ear treatments.
Area of Science:
- Otolaryngology
- Pharmacology
- Toxicology
Background:
- Methylene blue is a versatile medical agent, utilized as a dye and photosensitizer in antimicrobial photodynamic therapy.
- Its efficacy against multi-resistant bacteria is established, but its ototoxic potential remains unexplored.
Purpose of the Study:
- To investigate the ototoxic potential of methylene blue.
- To determine the safety of methylene blue for otologic applications.
Main Methods:
- A prospective animal study was conducted on guinea pigs.
- Animals received intratympanic injections of methylene blue, gentamicin, or normal saline.
- Auditory-evoked brainstem response and caspase-3 analysis were performed.
Main Results:
- Methylene blue injections showed no statistically significant hearing loss compared to saline.
- Gentamicin injections resulted in significant hearing loss (P < 0.001).
- Caspase-3 (apoptotic marker) was negative in the methylene blue group.
Conclusions:
- Intratympanic methylene blue injections demonstrated no ototoxic potential.
- Further studies are warranted to explore methylene blue's use in otology.
