Each sustained-release tablet for oral administration contains:

Hyoscyamine Sulfate . . . 0.375 mg

Hyoscyamine sulfate is one of the principal anticholinergic/antispasmodic components of belladonna alkaloids.

Hyoscyamine sulfate is Benzeneacetic acid, α-(hydroxymethyl)-, 8- methyl-8-azabicyclo[3.2.1]oct-3-yl ester, [3(S)- endo]-, sulfate (2:1), dihydrate.

(C 17H 23NO 3) 2•H 2SO 4•2H 2O
M.W. 712.85

Inactive ingredients include: calcium phosphate dibasic, ethylcellulose, green dye, lactose monohydrate, magnesium stearate (veg.), microcrystalline cellulose, and stearic acid.

Hyoscyamine has actions similar to those of atropine, but is more potent in both its central and peripheral effects. This product inhibits gastrointestinal propulsive motility and decreases gastric acid secretions. This product controls excessive pharyngeal, tracheal, and bronchial secretion. Once absorbed, this product disperses rapidly in the blood and is distributed throughout the entire body. The majority of hyoscyamine sulfate is excreted in the urine unchanged within the first 12 hours and only traces of hyoscyamine sulfate are found in the breast milk.

This product may be used in functional intestinal disorders to reduce symptoms such as those seen in mild dysenteries and diverticulitis. It can also be used to control gastric secretion, visceral spasm and hypermotility in cystitis, pylorospasm and associated abdominal cramps. Along with appropriate analgesics, this product is indicated in symptomatic relief of biliary and renal colic and as a drying agent in the relief of symptoms of acute rhinitis. This product is effective as adjunctive therapy in the treatment of peptic ulcer and irritable bowel syndrome, acute enterocolitis and other functional gastrointestinal disorders.

Glaucoma, obstructive uropathy, obstructive diseases of the gastrointestinal tract, paralytic ileum, intestinal atony of elderly or debilitated patients, unstable cardiovascular status, severe ulcerative colitis, toxic megacolon, myasthenia gravis, and myocardial ischemia. This product is not recommended for use in children under twelve years of age.

Heat prostration can occur with drug use in the event of high environmental temperature. Diarrhea may be an early symptom of incomplete intestinal obstruction, especially in patients with ileostomy or colostomy; in this instance, treatment would be inappropriate and possibly harmful. This product may cause drowsiness or blurred vision. Patients taking this product should be warned not to engage in activities requiring mental alertness such as operating a motor vehicle or other machinery or to perform hazardous tasks while taking this drug.

Not all of the following adverse reactions have been reported with hyoscyamine sulfate. The following adverse reactions have been reported for pharmacologically similar drugs with anticholinergic- antispasmodic action. Adverse reactions may include dryness of the mouth, urinary hesitancy and retention; blurred vision; tachycardia; palpitations; mydriasis; cycloplegia; increased ocular tension; loss of taste; headache; nervousness; drowsiness; weakness; dizziness; insomnia; nausea; vomiting; impotence; suppression of lactation; constipation; bloated feeling; allergic reactions or drug idiosyncrasies; urticaria and other dermal manifestations; ataxia; speech disturbance; some degree of mental confusion and/or excitement (especially in elderly persons); and decreased sweating.

The signs and symptoms of overdose are headache, nausea, vomiting, blurred vision, dilated pupils, hot dry skin, dizziness, dryness of the mouth, difficulty in swallowing and CNS stimulation. Measures to be taken are immediate lavage of the stomach and injection of physostigmine 0.5 to 2 mg intravenously and repeated as necessary up to a total of 5 mg. Fever may be treated symptomatically (tepid water sponge baths, hypothermic blanket). Excitement to a degree which demands attention may be managed with sodium thiopental 2% solution given slowly intravenously or chloral hydrate (100-200 mL of a 2% solution) by rectal infusion. In the event of progression of the curare-like effect to paralysis of the respiratory muscles, artificial respiration should be instituted and maintained until effective respiratory action returns.

In rats, the LD 50 for hyoscyamine is 375 mg/kg. Hyoscyamine is dialyzable.

Adults and children 12 years or older: 1 or 2 tablets every 12 hours. Dosage may be adjusted to 1 tablet every 8 hours if needed. Do not exceed 4 tablets in 24 hours. Tablets should be swallowed whole.

Note: Geriatric patients may be more sensitive to the effects of the usual adult dose.

Symax®-SR is supplied as green, capsule shaped tablets debossed “SR 375” on one side and plain on the opposite side. Available in bottles of 100 tablets, NDC 64543-112-01.

Figure 1: Bottle Label