What are the potential causes of lip smacking in an elderly patient with brittle asthma and a complex medical history?

Causes of Lip Smacking

Lip smacking in an elderly patient with brittle asthma is most commonly caused by medication side effects (particularly from beta-agonists and anticholinergics), tardive dyskinesia from other medications, focal seizures, or oral/dental discomfort—not the asthma itself.

Medication-Related Causes (Most Likely in This Context)

Beta-Agonist Effects

• Chronic or high-dose beta-agonist use (common in brittle asthma management) can cause oral motor side effects including tremor, dry mouth, and repetitive oral movements 1, 2.
• Patients with Type 1 brittle asthma often require continuous subcutaneous terbutaline or salbutamol infusions, which significantly increase systemic beta-agonist exposure 2, 3.
• Beta-receptor stimulation can produce involuntary muscle movements, particularly with the high doses needed in brittle asthma 3.

Anticholinergic Medication Effects

• Ipratropium bromide and other anticholinergics used in severe asthma cause profound dry mouth 4.
• Xerostomia (dry mouth) triggers compensatory lip smacking and tongue movements as patients attempt to generate saliva 4.

Corticosteroid-Related Issues

• Oral thrush (candidiasis) from inhaled or systemic corticosteroids causes oral discomfort leading to repetitive mouth movements 5.
• Patients with brittle asthma frequently require high-dose inhaled steroids plus oral steroids, increasing thrush risk 1, 6.

Neurological Causes

Tardive Dyskinesia

• Repetitive, involuntary movements of the lips, tongue, and jaw from chronic use of antipsychotics or metoclopramide 6.
• Particularly relevant given that patients with brittle asthma have significantly higher rates of psychiatric comorbidity and may be on psychotropic medications 6.
• The study found 12/20 patients with brittle asthma had intercurrent or past psychiatric disorders compared to 5/20 controls 6.

Focal Seizures

• Focal motor seizures can manifest as repetitive oral automatisms including lip smacking, chewing, or tongue movements.
• Consider if episodes are stereotyped, brief, and associated with altered awareness.

Metabolic and Systemic Causes

Electrolyte Disturbances

• Hypokalemia and hypomagnesemia from chronic beta-agonist use can cause neuromuscular irritability 4.
• Monitoring of potassium and magnesium is specifically recommended in patients receiving intensive bronchodilator therapy 4.

Hypoxia or Hypercapnia

• Severe asthma with oxygen saturation <92% or elevated CO2 can cause altered mental status and abnormal movements 5, 7.
• Life-threatening features include confusion, which may be accompanied by oral motor abnormalities 5.

Oral/Dental Causes

• Ill-fitting dentures, oral ulcers, or dental pain causing repetitive mouth movements.
• Dry mouth from medications exacerbates dental problems.

Critical Clinical Approach

Immediate Assessment Required

1. Check oxygen saturation and peak expiratory flow to rule out severe asthma exacerbation 7, 4.
2. Review all medications systematically, particularly beta-agonists (dose and delivery method), anticholinergics, corticosteroids, and any psychotropic drugs 4, 2.
3. Examine the oral cavity for thrush, ulcers, or dental pathology 5.
4. Assess mental status for confusion or altered consciousness suggesting severe hypoxia 5, 7.

Medication Audit Priorities

• Document total daily beta-agonist exposure (inhaled, nebulized, subcutaneous) 2, 3.
• Note if patient is on continuous subcutaneous terbutaline/salbutamol infusion, which is used in Type 1 brittle asthma 2, 3.
• Check for sedatives or anxiolytics, which are absolutely contraindicated in asthmatic patients 4.

Laboratory Evaluation

• Serum potassium and magnesium levels given chronic beta-agonist use 4.
• Consider arterial blood gas if respiratory distress present 5.

Common Pitfalls to Avoid

• Do not dismiss as anxiety or stress without thorough medication review, despite the known psychiatric comorbidity in brittle asthma 6.
• Do not assume it's related to asthma severity alone—the lip smacking is a separate issue requiring distinct evaluation.
• Do not overlook medication-induced movement disorders in patients on multiple drugs for complex medical conditions.
• Never administer sedatives to manage presumed anxiety in asthmatic patients, as benzodiazepines and opioids are contraindicated and can cause respiratory depression 4.