Topical Intranasal Co-Phenylcaine Affects Olfactory Assessment
Applied/Translational Research
Care Continuum
Singapore Health Biomedical Congress
National Healthcare Group
6 January 2026
To determine if topical intranasal cophenylcaine affects olfactory assessment To determine how long its effects persist for. Administration of topical intranasal cophenylcaine has a clinically significant impact on olfactory assessment and can last beyond 90.
Year Submitted: 2025
Published Date: 06 January 2026
Tags: Applied/Translational Research, Care Continuum, Quality Of Life, Quantitative Research
About this Content
Aims
To determine if topical intranasal cophenylcaine affects olfactory assessment
To determine how long its effects persist for
Background
With an increasingly healthy population focused on
improving quality of life, and the recent COVID-19
pandemic with its high prevalence of COVID-19 associated
olfactory dysfunction, there has been renewed interest and
awareness in olfactory disorders. Patients presenting to our
clinic with olfactory dysfunction are first evaluated with
nasoendoscopy to exclude any sinonasal pathology, before
a Sniffin Sticks (SS) test is performed to grade their
olfactory function.
Topical intranasal co-phenylcaine, comprising a
decongestant (phenylephrine) and an anaesthetic
(lidocaine), is commonly used prior to nasoendoscopic
evaluation of olfactory dysfunction. However, its effect on
subsequent olfactory assessment is unclear. This pilot aims
to study 1) if topical intranasal co-phenylcaine affects
olfactory assessment and 2) how long its effects last for.
Methods
20 adults with no self-reported smell loss, sinonasal disease
or prior nasal surgery were recruited to our study
voluntarily. They underwent SS Threshold and
Discrimination olfactory assessment and nasoendoscopy at
baseline, at 15 minutes and at 90 minutes after intranasal
co-phenylcaine was administered.
The maximum score is 16 for each SS component, with
higher scores indicating better olfactory function.
The Minimal Clinically Important Difference (MCID) of the
SS test was defined as 2.5 points for Threshold testing and
3 points for Discrimination testing.
Results
As a cohort, the mean SS Threshold score was 12.8 +-3.5
pre-spray, 11.4 +-4.6 15 minutes post-spray and 13.3 +-2.8
90 minutes post-spray (p=0.04).Though statistically
significant the change in scores did not meet MCID.
The mean SS Discrimination score was 12.1 +-1.4 prespray, 11.8 +-2.0 15 minutes post-spray and 11.8 +-2.8 90
minutes post-spray (p=0.84).
Individually, however, 45% of participants experienced
changes in SS Threshold scores meeting MCID at 15
minutes post-spray and 20% of participants experienced
changes persisting till 90 minutes post-spray (Chart 1a).
20% of participants experienced changes in SS
Discrimination scores meeting MCID at 15 minutes postspray and 35% of participants experienced changes in
Discrimination scores meeting MCID at 90 minutes postspray (Chart 1b)
Conclusion
Administration of topical intranasal cophenylcaine has a
clinically significant impact on olfactory assessment and
can last beyond 90 minutes. This is in contrast to the
available literature. Clinicians should avoid using cophenylcaine if intending to proceed with olfactory
assessment.
Lessons Learnt
Patients scheduled for Sniffin Sticks smell testing should not have their tests done within 90 minutes of co-phenylcaine administration. It may be preferable for the smell tests to be done on another day after the initial clinical visit.
Additional Information
SHBC Singapore Clinician Investigator Award - Merit
Keywords
Sniffin Sticks, olfaction, smell test
Innovators' Details
Innovators' Details
Healthcare Cluster(s) | National Healthcare Group |
Organization(s) Involved | Woodlands Hospital |
Platform(s) | Singapore Health Biomedical Congress |
Healthcare Professional Group(s) | Medical |
Applicable Specialty or Discipline | Otolaryngology |
Project Lead(s) | Lim Quan Qing Richmond |
Project Member(s) | Yew Wan Xin |
Connect with this contributor!
Lim Quan Qing Richmond - richmond.lim@nhghealth.com.sg