The goal of this clinical trial is to learn how the muscle relaxant tizanidine affects the acoustic reflex in adults. The acoustic reflex is a natural protection system of the ear that helps reduce the impact of loud sounds. It is not known whether tizanidine changes how this reflex works.

The main question this study aims to answer is:

Does taking tizanidine for 1 week change acoustic reflex thresholds in the same person when comparing before and after treatment? Participants who receive tizanidine will undergo hearing and acoustic reflex tests before treatment and again at the end of the treatment period.

Tizanidine is a commonly used muscle relaxant prescribed for musculoskeletal pain. Its relaxing effect on body muscles is well known. However, it is not clear whether tizanidine also affects the small middle ear muscle responsible for the acoustic reflex.

The acoustic reflex is a natural protection system of the ear. When a loud sound occurs, a tiny muscle called the stapedius contracts. This contraction reduces the amount of sound energy that reaches the inner ear and helps protect the inner ear and auditory nerve from acoustic damage. If this reflex does not work properly, a person may become more sensitive to loud sounds and may be more vulnerable to noise-related ear injury.

Only a few studies have looked at how muscle relaxant medications influence the acoustic reflex, and most have focused on drugs used during anesthesia. There is very little information about tizanidine, which is used in daily clinical practice for muscle and joint pain. Because of this gap, it is important to understand whether tizanidine changes the strength or timing of the acoustic reflex.

This single-arm clinical study will follow adults who are already planned to receive tizanidine as part of their treatment. Participants will take tizanidine 6 mg by mouth once a day for 1 week. Hearing and acoustic reflex tests will be performed at two time points: before starting tizanidine and at the end of the treatment period. The same standardized audiological methods will be used at both time points, including tympanometry and acoustic reflex measurements in both ears.

The main goal is to compare acoustic reflex measurements before and after tizanidine treatment in the same participants. By evaluating changes in acoustic reflex thresholds, amplitudes, and response patterns, the study aims to determine whether tizanidine has a measurable effect on stapedius muscle function. If the results suggest that tizanidine weakens or delays the acoustic reflex, this could mean that patients taking tizanidine may need to avoid excessive noise exposure during treatment. The findings may help clinicians better understand the auditory safety of muscle relaxant therapy and guide practical advice for patients.

Inclusion Criteria:

• Voluntary participation and ability to provide informed consent
• Age 18 years or older
• Currently receiving tizanidine 6 mg once daily as part of clinical care
• No active middle ear disease that could affect tympanometric or acoustic reflex measurements
• No chronic neuromuscular disease
• Ability to complete audiological testing

Exclusion Criteria:

• Refusal to participate
• Withdrawal of consent at any time
• Age under 18 years
• Presence of any ear condition that affects the acoustic reflex (e.g., otitis media, tympanic membrane perforation, otosclerosis)
• Presence of chronic neuromuscular disease
• Current alcohol or substance use disorder
• Any condition preventing completion of acoustic reflex or tympanometry testing

Individual participant data will not be shared due to institutional restrictions on the external sharing of personal health information.