Kwells

Action

Acts as competitive inhibitor at postganglionic muscarinic receptor sites of parasympathetic nervous system and on smooth muscles that respond to acetylcholine but lack cholinergic innervation. May block cholinergic transmission from vestibular nuclei to higher CNS centers and from reticular formation to vomiting center.

Availability

Injection: 1 mg/ml in 1-ml vials, 0.4 mg/ml in 0.5-ml ampules and 1-ml vials, 0.86 mg/ml in 0.5-ml ampules

Transdermal system (Transderm-Scop): 1.5 mg/patch (releases 0.5 mg scopolamine over 3 days)

Indications and dosages

➣ Preanesthetic sedation and obstetric amnesia

Adults: 0.3 to 0.6 mg I.M., I.V., or subcutaneously 45 to 60 minutes before anesthesia, usually given with analgesics

➣ Postoperative nausea and vomiting

Adults: One transdermal patch placed behind ear on evening before surgery and kept in place for 24 hours after surgery. For cesarean section, one transdermal patch placed behind ear 1 hour before surgery.

➣ Motion sickness

Adults: One transdermal patch placed behind ear 4 hours before anticipated need, replaced q 3 days if needed

Contraindications

• Hypersensitivity to scopolamine, other belladonna alkaloids, or barbiturates

• Hypersensitivity to bromides (injection only)

• Angle-closure glaucoma

• Acute hemorrhage

• Myasthenia gravis

• Obstructive uropathy (including prostatic hypertrophy)

• Obstructive GI disease (including paralytic ileus and intestinal atony)

• Reflux esophagitis

• Ulcerative colitis or toxic megacolon

• Hepatic or renal impairment

• Chronic lung disease (with repeated doses)

Precautions

Use cautiously in:

• suspected intestinal obstruction; pulmonary or cardiac disease; tachyarrhythmia or tachycardia; open-angle glaucoma; autonomic neuropathy; hypertension; hyperthyroidism; ileostomy or colostomy

• history of seizures or psychosis

• elderly patients

• pregnant or breastfeeding patients (safety not established)

• children.

Administration

• For I.V. use, give by direct injection at prescribed rate after diluting with sterile water.

• After removing protective strip from transdermal patch, avoid finger contact with exposed adhesive layer to prevent contamination.

Adverse reactions

CNS: drowsiness, dizziness, confusion, restlessness, fatigue

CV: tachycardia, palpitations, hypotension, transient heart rate changes

EENT: blurred vision, mydriasis, photophobia, conjunctivitis

GI: constipation, dry mouth

GU: urinary hesitancy or retention

Skin: decreased sweating, rash

Interactions

Drug-drug. Antidepressants, antihistamines, disopyramide, quinidine: additive anticholinergic effects

Antidepressants, antihistamines, opioid analgesics, sedative-hypnotics: additive CNS depression

Oral drugs: altered absorption of these drugs

Wax-matrix potassium tablets: increased GI mucosal lesions

Drug-herbs. Angel's trumpet, jimsonweed, scopolia: increased anticholinergic effects

Drug-behaviors. Alcohol use: increased CNS depression

Patient monitoring

• Assess vital signs and neurologic, cardiovascular, and respiratory status.

• Monitor patient for urinary hesitancy or retention.

Patient teaching

• Tell patient transdermal patch is most effective if applied to dry skin behind ear 4 hours before traveling.

• Caution patient to avoid touching exposed adhesive layer of transdermal patch.

• Advise patient to wash and dry hands thoroughly before and after applying patch.

• If patch becomes dislodged, instruct patient to remove it and apply new patch on a different site behind ear.

• Tell patient that using patch for more than 72 hours may cause withdrawal symptoms (headache, nausea, vomiting, dizziness). Advise him to limit use when feasible.

• Inform patient that his eyes may be markedly sensitive to light during patch use. Instruct him to wear sunglasses and use other measures to guard eyes from light.

• Caution patient to avoid alcohol because it may increase CNS depression.

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