From the FDA Drug Label
PRECAUTIONS General:Use with caution in patients with: autonomic neuropathy, hyperthyroidism, coronary heart disease, congestive heart failure, cardiac arrythmias, hypertension, and renal disease. Investigate any tachycardia before giving any anticholinergic drug since they may increase the heart rate. Use with caution in patients with hiatal hernia associated with reflux esophagitis We do not give Levsin (hyoscyamine) in the following situations:
- Autonomic neuropathy
- Hyperthyroidism
- Coronary heart disease
- Congestive heart failure
- Cardiac arrythmias
- Hypertension
- Renal disease
- Tachycardia (without investigation)
- Hiatal hernia associated with reflux esophagitis (without caution) 1
From the Research
Levsin (hyoscyamine) should not be given to patients with myasthenia gravis, glaucoma, obstructive gastrointestinal disorders, urinary retention, severe ulcerative colitis, toxic megacolon, or unstable cardiovascular status. The medication works by blocking acetylcholine receptors, reducing smooth muscle spasms, but this mechanism also creates potentially dangerous effects in susceptible individuals, such as exacerbating muscle weakness in myasthenia gravis patients, as discussed in studies like 2 and 3. Some key conditions to avoid when prescribing Levsin include:
- Myasthenia gravis, as it can worsen muscle weakness, as seen in patients with ocular myasthenia gravis 2
- Glaucoma, especially narrow-angle glaucoma, due to increased intraocular pressure
- Obstructive gastrointestinal disorders, such as pyloric stenosis, intestinal atony, or paralytic ileus, as Levsin can decrease GI motility
- Urinary retention or bladder neck obstruction, including prostatic hypertrophy, due to anticholinergic effects that can worsen urinary retention
- Severe ulcerative colitis, toxic megacolon, or unstable cardiovascular status, particularly tachycardia, as these conditions can be exacerbated by Levsin's mechanism of action. Caution is also warranted in elderly patients, who are more sensitive to anticholinergic side effects like confusion, and in patients with hyperthyroidism, where it may exacerbate symptoms.