Causality assessment · Causality: well established

Terbinafine and Taste disturbance (ageusia/dysgeusia): is the FAERS signal real?

n=273 co-reports · PRR 32.5 · ROR 33.7

Terbinafine side-effect profile All assessments See in the full list

A written Bradford Hill assessment of one drug–event pair. The grade is a judgement about the signal, not a statement that this drug causes this event in any one person; FAERS counts are reports, not rates.

Causality: well established

Terbinafine ↔ Taste disturbance (ageusia/dysgeusia)

n=273 co-reports · PRR 32.5 · ROR 33.7

Terbinafine commonly disturbs the sense of taste, most famously causing loss of taste (ageusia) or altered taste (dysgeusia) that can impair appetite and quality of life. The effect typically appears weeks into therapy and usually recovers slowly after the drug is stopped. It is a genuine, well-recognised drug effect rather than an idiosyncratic one-off. The 273 co-reports (PRR 32.5) reflect both the real effect and terbinafine's wide use for fungal nail and skin infections.

Regulatory basis: terbinafine prescribing information (taste disturbance, including loss of taste). Established terbinafine-dysgeusia literature.

Bradford Hill viewpoint	Status	Note
Temporality (necessary)	met	Taste disturbance appears weeks into therapy and usually recovers after withdrawal
Strength	met	PRR 32 on a modest co-report count
Consistency	met	Reproduced across case series and in trial data
Specificity	met	A characteristic terbinafine effect among antifungals
Biological gradient	partial	Broadly dose- and duration-related
Plausibility	met	Likely effect on taste-bud or nerve function is proposed
Coherence	met	Coheres with the labelled taste-disturbance warning
Experiment	met	A randomized trial recorded ageusia only in the terbinafine arm
Analogy	met	Analogous to taste disturbance from certain other drugs

This page's own qualitative read, not an automated/citation-gated assessment.

✓ Trial evidence found — A Study to Evaluate Efficacy and Safety of Four Posaconazole Regimens With Placebo and Terbinafine in the Treatment of Toenail Onychomycosis (Study P05082AM2)(COMPLETED) (NCT00491764), N=216

Term (as recorded)	Posaconazole 100 mg QD for 24 Weeks (n=36)	Posaconazole 200 mg QD for 24 Weeks (n=37)	Posaconazole 400 mg QD for 24 Weeks (n=36)	Posaconazole 400 mg QD for 12 Weeks (n=36)	Terbinafine 250 mg QD for 12 Weeks (n=36)	Placebo for 24 Weeks (n=35)
AGEUSIA — Nervous system disorders	0	0	0	0	2	0

Ageusia (loss of taste) was recorded only in the terbinafine arm (2 of 36 patients) and in none of the four posaconazole arms or placebo — a small but arm-specific confirmation of terbinafine's well-known taste-disturbance signal. View on ClinicalTrials.gov →