Phantosmia and Benzodiazepine Withdrawal: A Case Report

TL;DR

A woman experienced a bad smell hallucination after stopping clonazepam, a benzodiazepine, and her symptoms went away when she restarted the medication.

Contribution

This is the first reported case linking olfactory hallucinations to benzodiazepine withdrawal.

Findings

Olfactory hallucinations can occur as a symptom of benzodiazepine withdrawal.

Restarting clonazepam resolved the hallucinations and related symptoms promptly.

The case highlights the need for provider and patient education on benzodiazepine discontinuation.

Abstract

Olfactory hallucinations, known as phantosmia, involve the perception of smell without the presence of existing chemical stimuli and are usually described as unpleasant. Other than a single brief mention as one of the symptoms of benzodiazepine withdrawal, olfactory hallucinations are not specifically listed as a symptom of benzodiazepine withdrawal in the common literature.

We report the case of an older female with no previous history of psychosis, taking clonazepam for anxiety for five years. She was instructed by her outpatient provider to stop clonazepam before her elective surgery. Due to fear of mixing oxycodone prescribed for postoperative pain, the patient did not resume taking clonazepam during the hospitalization after surgery. No education was provided about benzodiazepine withdrawal or its symptoms. After discharge, she continued to hold clonazepam and started to experience a series of symptoms, such as insomnia, increased sensitivity to smell, and hearing music in her ears. On the day of admission, 14 days after her last clonazepam, she presented with the perception of an unpleasant odor, which she described as “bad” and “evil.” Clonazepam was restarted, and all symptoms promptly resolved.

To the best of our knowledge, no such case has been reported before. This case illustrates a rare presentation of olfactory hallucinations most likely precipitated by benzodiazepine withdrawal that was completely reversed by restarting the medication. In addition, it emphasizes the importance of providers and patient education regarding safe benzodiazepine discontinuation and raising awareness that olfactory hallucinations may present as a symptom of benzodiazepine withdrawal.