Effects of Isotretinoin on Smell

NCT ID: NCT07309341

Last Updated: 2025-12-30

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: NA
• Total Enrollment: 54 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-06-01
• Study Completion Date: 2026-06-01

Brief Summary

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 (NOSE and 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.

Detailed Description

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.

Conditions

Smell Dysfunction

Keywords

olfaction; smell disfunction; isotretinoin

Study Design

• Allocation Method: NA
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

Isotretinoin Treatment Group

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.

Group Type: EXPERIMENTAL

isotretinoin

Intervention Type: DRUG

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.

Interventions

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.

Intervention Type: DRUG

Eligibility Criteria

Inclusion Criteria

• Diagnosed with acne and scheduled to start oral isotretinoin as part of routine dermatology care
• Willing to participate and able to give informed consent
• Not currently smoking
• No history of allergic rhinitis, sinusitis, or active upper respiratory infection
• No medical condition known to affect the sense of smell

Exclusion Criteria

• Younger than 18 years or older than 45 years
• Current cigarette smoking
• History of chronic sinonasal disease
• Any condition that would prevent completing the smell test
• Not willing to continue participation or withdrawal of consent at any time

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 45 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

The Scientific and Technological Research Council of Turkey

OTHER

Sponsor Role: collaborator

Uşak University

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Locations

Uşak University Faculty of Medicine

Uşak, Merkez, Turkey (Türkiye)

Site Status: RECRUITING

Countries

Turkey (Türkiye)

Central Contacts

Faruk Kadri Bakkal, MD, Asistant Professor

Role: CONTACT

Phone: +905059242255

Email: faruk.bakkal@usak.edu.tr

Neslihan Demirel Öğüt, MD, Associate Professor

Role: CONTACT

Email: neslihan.ogut@usak.edu.tr

Facility Contacts

Faruk Kadri Bakkal

Role: primary

Other Identifiers

1919B012412359

Identifier Type: OTHER_GRANT

Identifier Source: secondary_id

ISO51116

Identifier Type: -

Identifier Source: org_study_id