Risks of Atropine Drops for Drooling
Atropine for drooling carries significant anticholinergic side effects that frequently lead to treatment discontinuation, with the most common adverse effects being dry mouth, blurred vision, constipation, urinary retention, and behavioral changes—particularly in children with developmental disabilities. 1, 2
Common Anticholinergic Side Effects
The FDA-approved labeling identifies the following direct antimuscarinic adverse reactions that commonly occur with atropine use 1:
- Dry mouth (xerostomia) - the most frequent side effect 1
- Blurred vision and photophobia - occur commonly with therapeutic doses 1
- Tachycardia - frequently observed with chronic administration 1
- Anhidrosis (inability to sweat) - can produce heat intolerance, particularly concerning in children 1
- Constipation - especially problematic in elderly patients and children with limited mobility 1
- Difficulty with urination - may occur, particularly in elderly patients 1
Serious Warnings and Precautions
Cardiovascular Risks
Atropine-induced tachycardia poses significant risk in patients with coronary artery disease by increasing myocardial oxygen demand. 1 The FDA specifically warns that total dosing should be restricted to avoid detrimental cardiac effects 1.
Acute Glaucoma
Atropine may precipitate acute angle-closure glaucoma, representing a vision-threatening emergency 1.
Gastrointestinal Obstruction
Atropine may convert partial organic pyloric stenosis into complete obstruction 1.
Urinary Retention
Complete urinary retention may occur in patients with prostatic hypertrophy 1.
Respiratory Complications
Atropine may cause inspissation (thickening) of bronchial secretions and formation of viscid plugs in patients with chronic lung disease 1.
Pediatric-Specific Concerns
In children with developmental disabilities treated for drooling, research demonstrates that side effects are common and frequently prompt treatment discontinuation 2:
- Behavioral issues were particularly problematic with benzhexol (trihexyphenidyl), especially in males 2
- Poor head control and poor oromotor function predict poor treatment response 2
- Side effects offset therapeutic benefits in many cases 2
A pilot study of sublingual atropine eyedrops noted that several parents complained about difficult administration, though no irreversible side effects occurred 3.
Hypersensitivity Reactions
Occasional hypersensitivity reactions have been observed, especially skin rashes which in some instances progressed to exfoliation 1.
Evidence Quality Considerations
The evidence for atropine's efficacy in drooling is weak. A randomized controlled trial in cancer patients failed to demonstrate effectiveness of sublingual atropine over placebo 4. A systematic review concluded that no general conclusion could be made about anticholinergic drug efficacy for drooling in children with multiple handicaps 5.
Clinical Context Caveat
All the cardiac guidelines and FDA warnings cited above pertain to intravenous atropine use for bradycardia and life-threatening conditions 6, 7, not specifically for sublingual drops used for drooling management. However, the systemic anticholinergic effects remain relevant regardless of route when the drug achieves therapeutic levels 1.
Practical Risk Mitigation
When atropine is used for drooling despite limited evidence:
- Monitor for anticholinergic toxicity symptoms (fever, confusion, hallucinations) 6
- Ensure adequate hydration to prevent heat intolerance from anhidrosis 1
- Screen for glaucoma risk factors before initiation 1
- Assess for urinary retention, particularly in patients with neurological impairment 1
- Consider that glycopyrrolate may have fewer side effects than atropine for drooling management 2