What are the contraindications for scopolamine, especially in geriatric patients or those with a history of narrow-angle glaucoma, myasthenia gravis, obstructive uropathy, gastrointestinal obstruction, cardiovascular disease, or dementia?

Scopolamine Contraindications

Scopolamine is absolutely contraindicated in patients with narrow-angle glaucoma unless they have undergone laser iridotomy, and should be used with extreme caution in patients with myasthenia gravis, obstructive uropathy, and gastrointestinal obstruction. 1

Absolute Contraindications

Narrow-Angle Glaucoma

• Scopolamine is strictly contraindicated in untreated narrow-angle glaucoma due to its anticholinergic properties that can precipitate acute angle-closure attacks by causing pupillary dilation and blocking aqueous humor outflow 1, 2
• Case reports document acute angle-closure glaucoma developing within days of transdermal scopolamine patch application 2
• However, scopolamine is not contraindicated in open-angle glaucoma or in angle-closure glaucoma already treated with laser iridotomy, as these patients can safely use anticholinergics 3, 4
• Studies in open-angle glaucoma patients show no significant intraocular pressure changes with transdermal scopolamine, though pupil dilation and accommodation effects occur 4

Myasthenia Gravis

• Scopolamine is contraindicated in myasthenia gravis because anticholinergic agents interfere with acetylcholine transmission at the neuromuscular junction 1
• The drug can worsen muscle weakness and potentially precipitate myasthenic crisis 1

Obstructive Uropathy and Prostatic Hypertrophy

• Scopolamine is contraindicated in patients with obstructive uropathy, prostatic hypertrophy with urinary retention, or bladder outlet obstruction 1, 5
• Anticholinergic effects reduce detrusor muscle contractility and can precipitate acute urinary retention 1
• A post-void residual measurement may be useful before initiating therapy in patients at higher risk for retention 1

Gastrointestinal Obstruction

• Scopolamine is contraindicated in patients with gastrointestinal tract obstruction, stenosing peptic ulcer disease, or impaired gastric emptying 1, 5
• The drug's antimuscarinic effects reduce GI motility and can worsen obstructive conditions 1, 6

Cardiovascular Contraindications and Precautions

Cardiac Disease

• Scopolamine is contraindicated in patients with tachycardia, angina, and cardiac failure according to product monographs 5
• The drug should be used very cautiously in patients with cardiac arrhythmias, coronary insufficiency, or cardiac decompensation, and only when benefits clearly outweigh risks 1, 5
• Patients with these conditions require careful cardiac monitoring in environments with resuscitation equipment and trained staff readily available 5

Severe Hypertension

• Scopolamine should be avoided in patients with severe systemic arterial hypertension (≥200/110 mm Hg) 1

Special Population Considerations

Geriatric Patients

• Elderly patients are at increased risk for anticholinergic adverse effects including confusion, cognitive impairment, urinary retention, and cardiovascular instability 1, 6
• Scopolamine produces central sedative, amnestic effects, and can cause hallucinations, particularly at higher doses 6
• The drug should be used with heightened caution in older adults given their increased susceptibility to anticholinergic toxicity 1

Patients with Dementia

• While not explicitly listed as an absolute contraindication, anticholinergics like scopolamine can impair cognitive function and should be avoided or used with extreme caution in patients with dementia 1
• The risk of worsening confusion and delirium is substantial in this population 6

Common Pitfalls and Clinical Pearls

Glaucoma Assessment

• Routine history-taking about glaucoma type is essential before prescribing scopolamine 3
• Many clinicians inappropriately avoid anticholinergics in all glaucoma patients, when only untreated narrow-angle glaucoma is truly contraindicated 3
• Conversely, some clinicians pay insufficient attention to glaucoma risk, potentially causing harm 3
• Patients who have used scopolamine should be counseled post-procedure to present emergently if they experience eye pain, redness, decreased vision, nausea, vomiting, or headache 5

Drug Interactions

• Scopolamine potentiates anticholinergic effects when combined with other medications having anticholinergic properties 1
• The drug is contraindicated with solid oral potassium chloride due to reduced gastric emptying potentially increasing potassium absorption 1

Dosage Form Considerations

• Transdermal scopolamine patches minimize adverse effects compared to oral or parenteral administration due to more stable plasma concentrations and lower peak levels 6
• Oral scopolamine has limited bioavailability (only 2.6% excreted unchanged in urine) and undergoes significant first-pass metabolism 6
• The short half-life and dose-dependent adverse effects (hallucinations, vertigo, dry mouth, drowsiness) limit clinical use of non-transdermal formulations 6