An interventional study of isotretinoin in Smell Dysfunction, sponsored by Uşak University. Completed at 1 site in Turkey (Türkiye). Open to participants aged 18 Years to 45 Years. Per ClinicalTrials.gov, last updated 2026-07-13.
Sponsored by Uşak University · Not applicable, Interventional, and Basic science
Isotretinoin is a common medicine used to treat moderate to severe acne. It often causes dryness of the skin and the inside of the nose. Because a normal sense of smell depends on a healthy nasal lining, this dryness may affect how well a person can smell.
This study will examine whether isotretinoin treatment changes the sense of smell in adults with acne. Before starting isotretinoin, participants will complete a standardized smell test and two short questionnaires about nasal symptoms and quality of life: the Nasal Obstruction Symptom Evaluation (NOSE) scale and the 22-item Sino-Nasal Outcome Test (SNOT-22). After at least 4 weeks of treatment, the same smell test and questionnaires will be repeated.
By comparing results before and after treatment, the study will test the hypothesis that isotretinoin has a negative effect on olfactory function and may reduce patients' ability to smell.
Isotretinoin is a systemic retinoid widely used for the treatment of moderate to severe acne that does not respond adequately to conventional topical or oral therapies. Although highly effective, isotretinoin is known to cause mucocutaneous dryness, which may alter the nasal environment and potentially influence olfactory function. The sense of smell depends on the integrity of the olfactory epithelium, the moisture of the nasal mucosa, and the ability of odorant molecules to reach and dissolve within the mucus layer. Changes in these factors may lead to measurable reductions in olfactory sensitivity or identification ability.
Previous studies examining the effects of isotretinoin on olfaction have produced conflicting results. One investigation reported an increase in olfactory sensitivity during treatment, while another found a decrease in smell function using a different testing method. These inconsistent findings, combined with the limited number of available studies, highlight the need for further research using standardized and reproducible assessment tools.
This prospective clinical study will evaluate olfactory function in adults initiating isotretinoin therapy for dermatologic indications. Participants will undergo a structured olfactory assessment using the Connecticut Chemosensory Clinical Research Center (CCCRC) smell test, which includes both odor identification and discrimination components. In parallel, patient-reported nasal symptoms and sinonasal-related quality of life will be assessed using the NOSE and SNOT-22 questionnaires, allowing a broader understanding of subjective nasal changes that may accompany isotretinoin use.
All assessments will be performed at two time points: before the start of isotretinoin therapy and after a minimum of four weeks of continuous treatment. This within-subject design will allow comparison of pre-treatment and post-treatment measurements to determine whether isotretinoin produces quantifiable changes in olfactory performance. The study hypothesis is that isotretinoin may negatively affect olfactory function due to its well-recognized drying effects on the nasal mucosa.
The findings of this research may assist clinicians in counseling patients regarding potential sensory side effects of isotretinoin and may provide a basis for further investigations into the mechanisms by which systemic medications influence nasal physiology and smell perception.
70 studies on the registry are indexed under Olfaction Disorders; 18 are open to participants now.
This study's enrollment of 54 is close to the median of 60 across 49 interventional studies indexed under Olfaction Disorders.
Browse Olfaction Disorders studies →Uşak University is the lead sponsor of 80 studies on the registry; 10 are open to participants now.
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Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants in this arm will receive standard-of-care oral isotretinoin prescribed by the Dermatology Department for the treatment of acne vulgaris. The dosage and duration of isotretinoin therapy will follow routine clinical practice and will be determined by the treating dermatologist. Olfactory function and nasal symptom assessments will be performed before starting isotretinoin and after at least four weeks of treatment.
Drug: isotretinoin
Oral isotretinoin prescribed as standard-of-care treatment for acne vulgaris. The dosage, formulation, and duration of therapy will follow routine clinical practice and will be determined by the treating dermatologist based on the participant's clinical condition and body weight. Participants will typically receive daily oral isotretinoin for at least four weeks before the post-treatment assessments.
Change in Olfactory Function Score
Change in olfactory function from baseline to at least 4 weeks after initiation of oral isotretinoin therapy, measured using the Connecticut Chemosensory Clinical Research Center (CCCRC) smell test. The CCCRC test includes odor identification and odor discrimination components, and yields a composite score representing overall olfactory performance.
Time frame: Baseline and 4 weeks after starting isotretinoin treatment.
Plan to share: No — Individual participant data will not be shared because institutional policy does not permit external sharing of health-related data.
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This study is completed, as verified in Jun 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Isotretinoin
Uşak University