Researchers will compare oral flurbiprofen (%0.25) spray and ice cream to a placebo (a look-alike substance that contains no drug) to see if oral flurbiprofen (%0.25) spray and ice cream works to effect post-thyroidectomy throat pain and voice quality.

Participants will:

• Receive 1 puff of oral flurbiprofen (0.25%) spray or 105 ml of ice cream or 1 puff of oral spray prepared with drinking water (placebo) at 5 hours postoperatively according to randomization result
• Undergo voice analysis using Praat voice analysis (University of Amsterdam) at 6 hours postoperatively
• Undergo a visual analog scale for analgesia status at 6 hours postoperatively

Patients undergoing thyroidectomy will be randomized into three groups using a card selection method (this method will be used to ensure that patients' personal medication/food preferences do not affect the randomization). The first group will receive one puff of oral flurbiprofen (0.25%) spray (for pain palliation) at 5 hours post-operatively; the second group will receive 105 ml of frozen ice cream at 5 hours post-operatively; and the third group will receive one puff of spray prepared with drinking water at 5 hours post-operatively as a placebo.

At 6 hours post-operatively, voice analysis will be performed using Praat voice analysis (University of Amsterdam / Netherlands) and analgesia status will be analyzed using a visual analog scale to compare the two methods with each other and with the placebo.

Routine proton pump inhibitor, analgesic, and antiemetic treatments will be administered post-operatively. The patient's clinical follow-up will be documented by the lead investigator and the associate investigator. A case report form will be completed for each registered patient and signed by the lead investigator or co-investigator. This will also apply to records of patients who do not complete the study. If a patient withdraws from the study, the reason will be recorded on the case report form. If a patient withdraws from the study due to a treatment-limiting adverse event, every effort will be made to clearly document the outcome. All forms will be completed legibly with indelible ink. Corrections will be initialed and dated by the lead investigator or co-investigator. The investigator is responsible for the accuracy of the data transferred to the forms and will sign them to demonstrate their consistency with the recorded data.

Patients participating in the study will have their detailed pre-operative allergic status checked and will undergo close vital sign monitoring during the procedure. Volunteer patients may withdraw from the study at any stage at their own request.

This study will be conducted in full compliance with the principles of the "Helsinki Declaration" and the laws and regulations of our country, and will also adhere strictly to the principles outlined in good clinical practice.

It is the researcher's responsibility to obtain written informed consent from each individual participating in the study after explaining the aims, methods, objectives, and potential risks of the study, and before any action related to the study is taken. The researcher will use a consent form approved by the local ethics committee for this study, and each informed consent form will be appropriately signed and dated by the patient or, for individuals lacking or unable to give consent, by the patient's legally authorized representative and the person receiving consent.

The researcher or the person(s) they designate are entirely free to refuse to participate in the study or to withdraw from the study at any time for any reason. If new information regarding safety results in significant changes to the risk/benefit assessment, the consent form will be revised and updated as needed; all individuals, including those currently undergoing treatment, will be provided with the new information, a copy of the signed form will be given, and their consent to continue in the study will be obtained.

The investigator will report all adverse and serious adverse events to the local ethics committee and fulfill any additional local notification requirements.

The investigator will ensure the confidentiality of patient names and the protection of individual identities from unauthorized parties; patients will be identified only by their initials and randomization number on the case report form; any document identifying the patient will be kept in complete confidentiality by the principal investigator; in accordance with good clinical practice and legal requirements, the investigator may allow the appropriate legal authority(ies) to review patient files.

All protocol arrangements will require approval from the local ethics committee before any changes to the protocol are implemented, except where the change is necessary to eliminate an immediate risk or where the change only concerns logistical or administrative aspects.

The investigator may terminate the study as defined in the clinical trial agreement, and the principal investigator will notify the ethics committee in writing of the completion or early termination of the study.

The investigator will maintain adequate and accurate records to ensure that the study's administration is fully documented and that the study data can be subsequently verified. These documents will be classified into two separate categories: 1) The investigator's study file and 2) The patient's clinical resource documents.

The investigator's study file will contain protocols/modifications, approval and correspondence from the local ethics committee and licensing authority, a sample informed consent form, medication records, personnel histories and authorization documents, and other relevant documents/correspondence, etc. Furthermore, at the end of the study, the investigator will keep patient data in a human-readable format on a compact disc, including an audit sequence detailing all changes to the data, correspondence for resolving questions, and the reasons for the changes. This will also be kept in the investigator's study file.

The patient's clinical resource documents will include patient hospital/clinic records, physician and nurse notes, signed informed consent forms, and logbooks. The investigator will retain both types of documents for at least 15 years after the completion or termination of the study. After this period, documents may be destroyed in accordance with local regulations. Patient-identifying records within the study will be kept confidential; however, as an exception, these records may be provided to and inspected by government agencies. All information provided to the researcher by the sponsor will be considered confidential unless otherwise stated. Participants' personal identification information and audio recordings will be collected by the research supervisor and team. Unauthorized access will be restricted by the research supervisor.

This protocol and all appendices given to the individual (such as individual information forms or study descriptions used to obtain informed consent) will be submitted by the researcher to the local ethics committee. A written document stating the date of the local ethics committee meeting and the date of approval will be provided to the researcher before the study begins. Any changes to the protocol after obtaining local ethics committee approval will also be submitted by the researcher to the ethics committee in accordance with local procedures and regulatory requirements. As a result of the preliminary assessment for the study, the required sample size is determined to be at least 84 patients in total, with at least 28 patients in each group. In this case, the power of the test is expected to be approximately 90.68%.

The data set obtained from the study is expected to be analyzed using Analysis of Variance (ANOVA) if it meets the parametric test prerequisites, and Kruskal-Wallis test if it does not. For categorical variables, Pearson chi-square and Fisher's exact test analysis methods are foreseen. A p-value <0.05 will be considered statistically significant.

Inclusion Criteria:

• No history of neck surgery
• Age between 18-85 years
• Undergoing thyroidectomy
• Agreeing to participate in the study
• Operation duration between 60-120 minutes

Exclusion Criteria:

• History of neck surgery
• History of radiotherapy to the head and neck region
• Pre-operative or post-operative vocal cord paralysis
• Pre-operative phonetic disorder
• Pre-operative laryngeal pathology
• Being under 18 years of age
• Refusal to participate in the study
• Smoking
• Flurbiprofen allergy
• Lactose intolerance