hyoscyamine
Cystospaz

hyoscyamine sulfate
A-Spas S/L, Anaspaz, Cystospaz-M, Levsin, Levsin Drops, Levsin/SL, Levsinex Timecaps

Available forms
Available by prescription only
hyoscyamine
Tablets: 0.15 mg
hyoscyamine sulfate
Capsules (extended-release): 0.375 mg
Elixir: 0.125 mg/5 ml
Injection: 0.5 mg/ml
Oral solution: 0.125 mg/ml
Tablets: 0.125 mg
Tablets (extended-release): 0.375 mg
Tablets (S.L.): 0.125 mg

Indications and dosages
 GI tract disorders caused by spasm; adjunctive therapy for peptic ulcers. Adults: 0.125 to 0.25 mg P.O. or S.L. q.i.d. before meals and h.s.; 0.375 to 0.75 mg P.O. (extended-release form) q 12 hours; or 0.25 to 0.5 mg I.M., I.V., or S.C. q 4 hours b.i.d. to q.i.d. (Substitute oral form when symptoms are controlled.)
Children ages 2 to 12: 0.033 mg at about 10 kg (22 lb); 0.0625 mg at about 20 kg (44 lb); 0.0938 mg at about 40 kg (88 lb); 0.125 mg at about 50 kg (110 lb). May repeat q 4 hours, p.r.n. Maximum dose is 0.75 mg daily.
Children younger than age 2: 0.0125 mg at about 2.3 kg (5 lb); 0.0167 mg at about 3.4 kg (7.5 lb); 0.02 mg at about 5 kg (11 lb); 0.025 mg at about 6.8 kg (15 lb); 0.033 mg at about 10 kg (22 lb); 0.05 mg at about 15 kg (33 lb). May repeat q 4 hours, p.r.n. Maximum daily doses are 0.075 mg, 0.1 mg, 0.125 mg, 0.15 mg, 0.2 mg, and 0.275 mg, respectively.
 Endoscopy or hypotonic duodenography. Adults: 0.25 to 0.5 mg I.V., I.M., or S.C., 5 to 10 minutes before procedure.
 Preoperative medication. Adults and children older than age 2: 5 mcg/kg I.V., I.M., or S.C. 30 to 60 minutes before induction of anesthesia.

Pharmacodynamics
Antispasmodic and antiulcer actions: Hyoscyamine competitively blocks acetylcholine at cholinergic neuroeffector sites, decreasing GI motility and inhibiting gastric acid secretion.

Pharmacokinetics
Absorption: Well absorbed when taken orally.
Distribution: Well distributed throughout the body and crosses the blood-brain barrier. About 50% of dose binds to plasma proteins.
Metabolism: Metabolized in the liver. Usual duration of effect is up to 4 hours with standard oral and parenteral administration and up to 12 hours for the extended-release preparation.
Excretion: Excreted in the urine.

Contraindications and precautions
Contraindicated in patients with glaucoma, obstructive uropathy, obstructive disease of the GI tract, severe ulcerative colitis, myasthenia gravis, hypersensitivity to anticholinergics, paralytic ileus, intestinal atony, unstable CV status in acute hemorrhage, or toxic megacolon.
  Use cautiously in patients with autonomic neuropathy, hyperthyroidism, coronary artery disease, arrhythmias, heart failure, hypertension, hiatal hernia with reflux esophagitis, hepatic or renal disease, and ulcerative colitis. Also use cautiously in hot or humid environments where drug-induced heat stroke can occur.

Interactions
Drug-drug. Amantadine: Increases anticholinergic effects. Avoid use together.
Antacids, antidiarrheals: Decreases hyoscyamine absorption. Give hyoscyamine 1 hour before these drugs.
Antihistamines, phenothiazines, tricyclic antidepressants: Increases adverse anticholinergic effects of hyoscyamine. Avoid use together.
Haloperidol, phenothiazines: Reduces antipsychotic effectiveness. Monitor patient carefully.

Adverse reactions
CNS: fever, headache, insomnia, drowsiness, dizziness, nervousness, weakness, confusion and excitement in elderly patients.
CV: palpitations, tachycardia.
EENT: blurred vision, mydriasis, increased intraocular pressure, cycloplegia, photophobia.
GI: dry mouth, dysphagia, constipation, heartburn, loss of taste, nausea, vomiting, paralytic ileus.
GU: urinary hesitancy, urine retention, impotence.
Skin: urticaria, decreased sweating or possible anhidrosis, other dermal manifestations.
Other: allergic reactions.

Effects on lab test results
None reported.

Overdose and treatment
Signs and symptoms of overdose include curare-like symptoms, such as respiratory paralysis; central stimulation followed by depression; and such psychotic symptoms as disorientation, confusion, hallucinations, delusions, anxiety, agitation, and restlessness. Peripheral effects may include dilated, nonreactive pupils; blurred vision; flushed, hot, dry skin; dryness of mucous membranes; dysphagia; decreased or absent bowel sounds; urine retention, hyperthermia; headache; tachycardia; hypertension; and increased respiration.
 Treatment is primarily symptomatic and supportive, as needed. Maintain patent airway. If patient is alert, induce emesis (or use gastric lavage) and follow with a saline cathartic and activated charcoal to prevent further drug absorption. In severe cases, physostigmine may be administered to block antimuscarinic effects. Give fluids, as needed, to treat shock; diazepam to control psychotic symptoms; and pilocarpine (instilled into the eyes) to relieve mydriasis. If urine retention occurs, catheterization may be needed.

Special considerations
• Hyoscyamine is administered P.O. Hyoscyamine sulfate usually is administered P.O. or S.L. but may be given I.V., I.M., or S.C. when therapeutic effect is needed or if oral administration isn’t possible.
• Adjust drug regimen based on patient’s response and tolerance.
Breast-feeding patients
• Drug may appear in breast milk, possibly resulting in infant toxicity. Avoid use in breast-feeding women. Drug also may decrease milk production.
Pediatric patients
• Safety and efficacy for use in children haven’t been reported.
Geriatric patients
• Use drug cautiously in elderly patients; lower doses are indicated.

Patient education
• Advise patient to avoid driving or performing other hazardous activities if drowsiness, dizziness, or blurred vision occurs.
• Tell patient to drink fluids to avoid constipation.
• Instruct patient to report rash or other skin eruptions.
• Advise patient that extended-release tablets may not completely disintegrate and tablet fragments may be excreted in stools.
• Tell patient not to crush or chew extended-release tablets.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use