Does Clonazepam Have Anticholinergic Properties?
No, clonazepam does not have significant anticholinergic (antimuscarinic) properties—it is a benzodiazepine that acts primarily through GABA-A receptor enhancement, not muscarinic receptor blockade.
Mechanism of Action
Clonazepam works by enhancing the activity of gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system 1. This is fundamentally different from anticholinergic medications, which block muscarinic receptors.
Evidence from Guidelines
The 2021 Mayo Clinic polypharmacy guideline explicitly distinguishes between anticholinergic medications and benzodiazepines in their deprescribing recommendations 2:
- Anticholinergic medications (like diphenhydramine, cyclobenzaprine, oxybutynin) cause "broad muscarinic receptor blockade" resulting in impaired vision, urinary retention, constipation, and cognitive impairment
- Benzodiazepines (including clonazepam) are listed separately with different side effects: sedation, cognitive impairment, falls, and withdrawal syndromes—but not anticholinergic effects
The guideline specifically states that opioids have "anticholinergic properties" but makes no such claim about benzodiazepines like clonazepam 2.
Clinical Side Effect Profile
Multiple sleep medicine guidelines 3, 4, 5 consistently describe clonazepam's side effects as:
- Morning sedation
- Gait imbalance and falls
- Cognitive disturbances (delirium, amnesia)
- Respiratory depression
- Depression
Notably absent from these comprehensive lists are classic anticholinergic effects such as:
- Dry mouth
- Urinary retention
- Constipation
- Blurred vision
- Tachycardia
Important Clinical Caveat
One case report 6 described a patient taking multiple medications including clonazepam who developed severe hyperthermia attributed to "excessive anticholinergic effects." However, this patient was simultaneously taking amitriptyline, cyclobenzaprine, and benztropine—all of which are strongly anticholinergic medications. The hyperthermia was caused by the combination of truly anticholinergic drugs, not by clonazepam itself.
Practical Implications
- Do not count clonazepam when calculating anticholinergic burden scales or Drug Burden Index scores
- Clonazepam does not contribute to anticholinergic side effects like urinary retention, constipation, or dry mouth
- However, clonazepam does carry significant risks in older adults through its sedative and cognitive effects, warranting caution per Beers Criteria 3
- When a patient on clonazepam develops anticholinergic symptoms, look for other culprit medications
The distinction matters clinically: while both anticholinergics and benzodiazepines can impair cognition in older adults, they do so through entirely different mechanisms and require different management strategies.