What medications can cause a loss of sense of smell?

Medications That Can Cause Loss of Sense of Smell

Several medications can cause loss of sense of smell (anosmia) or smell distortion, with macrolide antibiotics like azithromycin being among the most well-documented causes. 1

Common Medication Classes Associated with Olfactory Dysfunction

Antibiotics

• Macrolides: Azithromycin is specifically documented to cause "taste/smell perversion/loss" as an adverse effect 1
• Aminoglycosides: Amikacin has been reported to cause reversible anosmia 2
• Other antibiotics: Doxycycline, amoxicillin, clarithromycin, roxithromycin, kanamycin, and streptomycin have been documented to cause olfactory disorders 2

Cardiovascular Medications

• ACE inhibitors can cause rhinitis which may affect smell function 1
• Calcium channel blockers may affect smell receptor function 3

Psychotropic Medications

• Tricyclic antidepressants and thioridazines can affect sensory function 1

Other Medications

• Phosphodiesterase-5 inhibitors 1
• Alpha-receptor antagonists 1
• NSAIDs including aspirin 1
• Intranasal medications causing rhinitis medicamentosa (rebound congestion from overuse of intranasal decongestants) 1

Mechanisms of Medication-Induced Smell Loss

Medications can impair olfactory function through several mechanisms:

1. Direct receptor inactivation: Drugs may inhibit odorant receptor binding or function 3
2. Disruption of signal transduction: Interference with G-protein function, inositol trisphosphate function, or ion channel activity 3
3. Inflammatory effects: Medications causing rhinitis can indirectly affect smell by causing nasal congestion and inflammation 1
4. Distortion of smell perception: Some drugs cause abnormal persistence of receptor activity or failure to properly inactivate receptors 3

Clinical Presentation and Assessment

Patients with medication-induced olfactory dysfunction may present with:

• Complete loss of smell (anosmia)
• Reduced smell sensitivity (hyposmia)
• Distorted smell perception (dysosmia or parosmia)

Assessment should include:

• Detailed medication history, including prescription, OTC, and recreational drugs
• Evaluation of onset timing in relation to medication use
• Validated olfactory function testing when available 4
• Nasal endoscopy to rule out other causes 4

Impact on Quality of Life

Smell loss significantly impacts quality of life:

• Reduced enjoyment of food and beverages
• Safety concerns (inability to detect gas leaks, smoke, spoiled food)
• Psychological effects including depression and anxiety 5
• Social implications and reduced quality of life 5

Management Approach

1. Identify the causative medication:

   • Review medication history and timing of smell loss onset

2. Consider medication modification:

   • If possible, discontinue the suspected medication (in consultation with prescribing physician)
   • Consider alternative medications with lower risk of olfactory effects

3. Monitor for recovery:

   • Most cases resolve with discontinuation of the offending medication 3
   • Recovery time varies from days to months

4. For persistent cases:

   • Olfactory training is recommended as first-line therapy 4
   • Consider intranasal corticosteroids if inflammation is present 4
   • Zinc supplementation may help in some cases 3

Prevention and Patient Education

• Inform patients about potential olfactory side effects when prescribing high-risk medications
• Advise patients to report smell changes promptly
• Recommend safety measures for patients with smell loss:
  • Install gas and smoke detectors
  • Check food expiration dates carefully
  • Exercise caution with gas appliances 4

Pitfalls to Avoid

• Overlooking medication-induced causes: Always consider medications in the differential diagnosis of new-onset smell disorders
• Assuming spontaneous recovery: While many cases resolve with medication discontinuation, some may persist and require specific treatment
• Underestimating impact: Don't dismiss the significant impact of smell loss on quality of life and safety
• Misattributing cause: Post-viral olfactory loss (e.g., after COVID-19) is common and may be confused with medication effects 4, 6

Early recognition and management of medication-induced olfactory dysfunction can significantly improve patient outcomes and quality of life.