hyoscyamine sulfate

Action

Competitively inhibits acetylcholine action at autonomic nerve sites, relaxing smooth muscle and decreasing glandular secretions

Availability

hyoscyamine

Tablets: 0.15 mg

hyoscyamine sulfate

Capsules (timed-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 (orally disintegrating): 0.125 mg

Tablets (sublingual): 0.125 mg

Indications and dosages

➣ Adjunct in GI tract disorders; pain and hypersecretion in pancreatitis; cystitis; renal colic; infant colic; acute rhinitis; rigidity, tremors, and hyperhidrosis in Parkinson's disease; partial heart block due to vagal activity

Adults and children ages 12 and older: 0.125 to 0.25 mg (sulfate) P.O. or S.L. two to four times daily, or 0.375 to 0.75 mg (extended-release sulfate) P.O. q 12 hours, or 0.25 to 0.5 mg (sulfate) subcutaneously, I.M., or I.V. two to four times daily p.r.n.

Children ages 2 to 12: In children weighing approximately 50 kg (110 lb), 0.125 mg (sulfate) P.O. q 4 hours p.r.n.; in children weighing approximately 20 kg (40 lb), 0.0625 mg P.O. (sulfate); in children weighing approximately 10 kg (22 lb), 0.031 to 0.033 mg (sulfate) P.O. Don't exceed 0.75 mg/day.

Children ages 2 and younger: In children weighing approximately 7 kg (15 lb), 0.025 (sulfate) P.O. q 4 hours p.r.n.; in children weighing approximately 5 kg (11 lb), 0.0208 mg (sulfate) P.O. q 4 hours p.r.n.; in children weighing approximately 3.4 kg (7.5 lb), 0.0167 mg (sulfate) P.O. q 4 hours p.r.n.; in children weighing approximately 2.3 kg (5 lb), 0.0125 mg (sulfate) P.O. q 4 hours p.r.n.

➣ Before endoscopy or hypotonic duodenography

Adults: 0.25 to 0.5 mg (sulfate) subcutaneously, I.M., or I.V. 5 to 10 minutes before procedure

➣ Preoperatively to inhibit salivation and excessive respiratory secretions

Adults and children older than age 2: 5 mcg/kg (sulfate) I.M., I.V., or subcutaneously 30 to 60 minutes before anesthesia induction

➣ Muscarinic toxicity

Adults: 1 to 2 mg (sulfate) I.V. Additional 1-mg doses may be given I.M. or I.V. q 3 to 10 minutes until muscarinic signs and symptoms subside; doses may be repeated if needed. Patient may need up to 25 mg during first 24 hours. For maintenance, 0.5 to 1 mg P.O. at intervals of several hours until signs and symptoms disappear.

Contraindications

• Hypersensitivity to anticholinergics, alcohol, sulfites, or tartrazine

• Angle-closure glaucoma, synechia

• GU or GI obstructive disease, severe ulcerative colitis

• Renal or hepatic disease

• Neonates or premature infants

Precautions

Use cautiously in:

• cardiovascular disease, prostatic hypertrophy, reflux esophagitis, brain damage, autonomic neuropathy, hyperthyroidism, glaucoma, Down syndrome, spastic paralysis

• elderly patients

• pregnant (safety not established) or breastfeeding patients

• infants and small children.

Administration

• Administer 30 to 60 minutes before meals and at bedtime.

• Give bedtime dose at least 2 hours after last evening meal or snack.

• Be aware that hyoscyamine is given P.O. only, whereas hyoscyamine sulfate may be given P.O., I.M., I.V., sublingually, or subcutaneously.

• Know that a cholinerase reactivator (pralidoxime) is given concomitantly to treat muscarinic toxicity.

Adverse reactions

CNS: confusion, excitement, nervousness, dizziness, light-headedness, headache, insomnia

CV: palpitations, tachycardia

EENT: blurred vision, cycloplegia, increased intraocular pressure, mydriasis, photophobia

GI: nausea, vomiting, constipation, bloating, dry mouth, paralytic ileus

GU: urinary hesitancy or retention, erectile dysfunction, lactation suppression

Skin: flushing, decreased sweating, urticaria, local irritation (with I.M., I.V., or subcutaneous use)

Other: altered taste, allergic reactions (including fever), heat intolerance, anaphylaxis

Interactions

Drug-drug. Amantadine, antihistamines, antiparkinsonian drugs, disopyramide, glutethimide, meperidine, procainamide, quinidine, tricyclic antidepressants: increased anticholinergic effects

Antacids: decreased hyoscyamine absorption

Atenolol: increased atenolol effects

Ketoconazole: interference with absorption of both drugs

Methotrimeprazine: increased risk of extrapyramidal effects

Phenothiazines: decreased phenothiazine effects, increased anticholinergic effects

Drug-herbs. Jimsonweed: adverse cardiovascular effects

Patient monitoring

• Watch for adverse reactions.

• Check for mental status changes, such as confusion.

• Evaluate fluid intake and output.

• Assess patient's response to temperature changes (especially hot weather). Drug may cause heat intolerance, predisposing patient to heat stroke.

Patient teaching

• Tell patient to take on empty stomach 30 to 60 minutes before meals and at least 2 hours after last evening meal or snack.

• Instruct patient with urinary hesitancy to empty bladder before taking.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and herbs mentioned above.

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